Tuning defects in oxides at room temperature by lithium reduction

Neighbouring Synergy in High-Density Single Ir Atoms on CoGaOOH for Efficient Alkaline Electrocatalytic Oxygen Evolution

The catalytic performance of single-atom catalysts was strictly limited by isolated single-atom sites. Fabricating high-density single atoms to realize the synergetic interaction in neighbouring single atoms could optimize the adsorption behaviors of reaction intermediates, which exhibited great potential to break performance limitations and deepen mechanistic understanding of electrocatalysis. However, the catalytic behavior governed by neighbouring single atoms is particularly elusive and has yet to be understood. Herein, we revealed that the synergetic interaction in neighbouring single atoms contributes to superior performance for oxygen evolution relative to isolated Ir single atoms. Neighbouring single atoms was achieved by fabricating high-density single atoms to narrow the distance between single atoms. Electrochemical measurements demonstrated that the Nei-Ir1/CoGaOOH with neighbouring Ir single atoms exhibited a low overpotential of 170 mV at a current density of 10 mA cm-2, and long-durable stability over 2000 h for oxygen evolution. Mechanistic studies revealed that neighbouring single atoms synergetic stabilized the *OOH intermediates via extra hydrogen bonding interactions, thus significantly reducing the reaction energy barriers, as compared to isolated Ir single atoms. The discovery of the synergetic interaction in neighbouring single atoms could offer guidance for the development of efficient electrocatalysts, thus accelerating the world's transition to sustainable energy.

Multienzyme-Like Polyoxometalate-Based Single-Atom Enzymes for Cancer-Specific Therapy Through Acid-Triggered Nontoxicity-to-Toxicity Transition

Single-atom enzymes (SAzymes) exhibit great potential for chemodynamic therapy (CDT); while, general application is still challenged by their instability and unavoidable side effects during delivery. Herein, a manganese-based polyoxometalate single-atom enzyme (Mn-POM SAE) is first introduced into tumor-specific CDT, which exhibits tumor microenvironment (TME)-activated transition of nontoxicity-to-toxicity. Different from traditional POM materials, the aggregates of low-toxic Mn-POM SAE nanospheres are obtained at neutral conditions, facilitating efficient delivery and avoiding toxicity problems in normal tissues. Under acid TME conditions, these nanospheres are degraded into smaller units of toxic Mn(II)-PW11; thus, initiating cancer cell-specific therapy. The released active units of Mn(II)-PW11 exhibit excellent multienzyme-like activities (including peroxidase (POD)-like, oxidase (OXD)-like, catalase (CAT)-like, and glutathione peroxidase (Gpx)-like activities) for the synergistic cancer therapy due to the stabilized high valence Mn species (MnIII/MnIV). As demonstrated by both intracellular evaluations and in vivo experiments, ROS is generated to cause damage to lysosome membranes, further facilitating acidification and impaired autophagy to enhance cancer therapy. This study provides a detailed investigation on the acid-triggered releasing of active units and the electron transfer in multienzyme-mimic-like therapy, further enlarging the application of POMs from catalytical engineering into cancer therapy.

Opening and Constructing Stable Lithium-ion Channels within Polymer Electrolytes

Lithium-ion batteries play an integral role in various aspects of daily life, yet there is a pressing need to enhance their safety and cycling stability. In this study, we have successfully developed a highly secure and flexible solid-state polymer electrolyte (SPE) through the in situ polymerization of allyl acetoacetate (AAA) monomers. This SPE constructed an efficient Li+ transport channel inside and effectively improved the solid-solid interface contact of solid-state batteries to reduce interfacial impedance. Furthermore, it exhibited excellent thermal stability, an ionic conductivity of 3.82×10-4 S cm-1 at room temperature (RT), and a Li+ transport number (tLi+) of 0.66. The numerous oxygen vacancies on layered inorganic SiO2 created an excellent environment for TFSI- immobilization. Free Li+ migrated rapidly at the C=O equivalence site with the poly(allyl acetoacetate) (PAAA) matrix. Consequently, when cycled at 0.5C and RT, it displayed an initial discharge specific capacity of 140.6 mAh g-1 with a discharge specific capacity retention rate of 70 % even after 500 cycles. Similarly, when cycled at a higher rate of 5C, it demonstrated an initial discharge specific capacity of 132.3 mAh g-1 while maintaining excellent cycling stability.

Synthesis of n-Propanol from CO2 Electroreduction on Bicontinuous Cu2O/Cu Nanodomains

n-propanol is an important pharmaceutical and pesticide intermediate. To produce n-propanol by electrochemical reduction of CO2 is a promising way, but is largely restricted by the very low selectivity and activity. How to promote the coupling of *C1 and *C2 intermediates to form the *C3 intermediate for n-propanol formation is challenging. Here, we propose the construction of bicontinuous structure of Cu2O/Cu electrocatalyst, which consists of ultra-small Cu2O nanodomains, Cu nanodomains and large amounts of grain boundaries between Cu2O and Cu nanodomains. The n-propanol current density is as high as 101.6 mA cm-2 at the applied potential of -1.1 V vs. reversible hydrogen electrode in flow cell, with the Faradaic efficiency up to 12.1 %. Moreover, the catalyst keeps relatively stable during electrochemical CO2 reduction process. Experimental studies and theoretical calculations reveal that the bicontinuous structure of Cu2O/Cu can facilitate the *CO formation, *CO-*CO coupling and *CO-*OCCO coupling for the final generation of n-propanol.

Catalytic Oxidation of Toluene over Pt/CeO2 Catalysts: A Double-Edged Sword Effect of Strong Metal-Support Interaction

Strong metal-support interaction (SMSI), which has drawn widespread attention in heterogeneous catalysis, is thought to significantly affect the catalytic performance for volatile organic chemical (VOC) abatement. In the present study, strong interactions between platinum and ceria are constructed by modulating the oxygen vacancy concentration of CeO2 through a NaBH4 reduction method. For a catalyst with higher content of oxygen vacancy, more electrons would transfer from ceria to Pt, which is attributed to the stronger effect of SMSI. The obtained electron-richer Pt sites exhibit higher ability for toluene activation, contributing to better performance for toluene oxidation. On the other hand, the stronger metal-support interaction would facilitate CeOx species migrating to the Pt nanoparticle surface and forming an encapsulated structure. Smaller Pt dispersion leads to fewer sites for toluene adsorption and activation, which is to the disadvantage of the reaction. Therefore, taking the negative and positive effects together, the Pt/CeO2-0.5 catalyst has the highest catalytic performance for toluene abatement. Our study provides new insights into strong metal-support interaction on toluene oxidation and contributes to designing noble metal catalysts for VOC abatement.

Interfacial Crosslinking for Efficient and Stable Planar TiO2 Perovskite Solar Cells

The buried interface between the electron transport layer (ETL) and the perovskite layer plays a crucial role in enhancing the power conversion efficiency (PCE) and stability of n-i-p type perovskite solar cells (PSCs). In this study, the interface between the chemical bath deposited (CBD) titanium oxide (TiO2) ETL and the perovskite layer using multi-functional potassium trifluoromethyl sulfonate (SK) is modified. Structural and elemental analyses reveal that the trifluoromethyl sulfonate serves as a crosslinker between the TiO2 and the perovskite layer, thus improving the adhesion of the perovskite to the TiO2 ETL through strong bonding of the ─CF3 and ─SO3 - terminal groups. Furthermore, the multi-functional modifiers reduced interface defects and suppressed carrier recombination in the PSCs. Consequently, devices with a champion PCE of 25.22% and a fill factor (FF) close to 85% is achieved, marking the highest PCE and FF observed for PSCs based on CBD TiO2. The unencapsulated device maintained 81.3% of its initial PCE after operating for 1000 h.

Achieving high selectivity and activity of CO2 electroreduction to formate by in-situ synthesis of single atom Pb doped Cu catalysts

Exploring highly selective and stable electrocatalysts is of great significance for the electrochemical conversion of CO2 into fuel. Herein, a three-dimensional (3D) nanostructure catalyst was developed by doping Pb single-atom (PbSA) in-situ on carbon paper (PbSA100-Cu/CP) through a low-energy and economical method. The designed catalyst exhibited abundant active sites and was beneficial to CO2 adsorption, activation, and subsequent conversion to fuel. Interestingly, PbSA100-Cu/CP showed a prominent Faraday efficiency (FE) of 97 % at -0.9 V versus reversible hydrogen electrode (vs. RHE) and a high partial current density of 27.9 mA·cm-2 for formate. Also, the catalyst remained significantly stable for 60 h during the durability test. The reaction mechanism was investigated by density functional theory (DFT), demonstrating that the doping PbSA induced the electrons redistribution, promoted the formate generation, reduced the rate-determining step (RDS) energy barrier, and inhibited the hydrogen evolution reaction. The study aims to provide a new strategy for developing of single-atom catalysts with high selectivity and stability, which will help reduce environmental pressure and alleviate energy problems.

Ultrafine CuO/graphene oxide cellulose nanocomposites with complementary framework for polycyclic aromatic hydrocarbon pollutants removal

Efficient and sustainable methods for eliminating polycyclic aromatic hydrocarbon pollutants (PAHPs) are in highly desired. Proven technologies involve physical and chemical reactions that absorb PAHPs, however they encounter formidable challenges. Here, a bottom-up refining-grain strategy is proposed to rationally design ultrafine CuO/graphene oxide-cellulose nanocomposites (LCelCCu) with a mirror-like for tetracycline (TC) to substantially improve the efficient of the purification process by active integrated-sorption. The LCelCCu captures TC with a higher affinity and lower energy demand, as determined by sorption kinetic, isotherms, thermodynamics, and infrared and X-ray Photoelectron Spectroscopy. The resulting material could achieve ultra-high sorption capacity (2775.23 mg/g), kinetic (1.2499 L g-1 h-1) and high selectivity (up to 99.9 %) for TC, nearly surpassing all recent adsorbents. This study simultaneously unveils the pioneering role of simultaneous multi-site match sorption and subsequent advanced oxidation synergistically, fundamentally enhancing understanding of the structure-activity-selectivity relationship and inspires more sustainable water purification applications and broader material design considerations.

Atomic Confinement Empowered CoZn Dual-Single-Atom Nanotubes for H2O2 Production in Sequential Dual-Cathode Electro-Fenton Process

Single-atom catalysts (SACs) are flourishing in various fields because of their 100% atomic utilization. However, their uncontrollable selectivity, poor stability and vulnerable inactivation remain critical challenges. According to theoretical predictions and experiments, a heteronuclear CoZn dual-single-atom confined in N/O-doped hollow carbon nanotube reactors (CoZnSA@CNTs) is synthesized via spatial confinement growth. CoZnSA@CNTs exhibit superior performance for H2O2 electrosynthesis over the entire pH range due to dual-confinement of atomic sites and O2 molecule. CoZnSA@CNTs is favorable for H2O2 production mainly because the synergy of adjacent atomic sites, defect-rich feature and nanotube reactor promoted O2 enrichment and enhanced H2O2 reactivity/selectivity. The H2O2 selectivity reaches ∼100% in a range of 0.2-0.65 V versus RHE and the yield achieves 7.50 M gcat -1 with CoZnSA@CNTs/carbon fiber felt, exceeding most of the reported SACs in H-type cells. The obtained H2O2 is converted directly to sodium percarbonate and sodium perborate in a safe way for H2O2 storage/transportation. The sequential dual-cathode electron-Fenton process promotes the formation of reactive oxygen species (•OH, 1O2 and •O2 -) by activating the generated H2O2, enabling accelerated degradation of various pollutants and Cr(VI) detoxification in actual wastewater. This work proposes a promising confinement strategy for catalyst design and selectivity regulation of complex reactions.

CeO2-Based Frustrated Lewis Pairs via Defective Engineering: Formation Theory, Site Characterization, and Small Molecule Activation

Activation of small molecules is considered to be a central concern in the theoretical investigation of environment- and energy-related catalytic conversions. Sub-nanostructured frustrated Lewis pairs (FLPs) have been an emerging research hotspot in recent years due to their advantages in small molecule activation. Although the progress of catalytic applications of FLPs is increasingly reported, the fundamental theories related to the structural formation, site regulation, and catalytic mechanism of FLPs have not yet been fully developed. Given this, it is attempted to demonstrate the underlying theory of FLPs formation, corresponding regulation methods, and its activation mechanism on small molecules using CeO2 as the representative metal oxide. Specifically, this paper presents three fundamental principles for constructing FLPs on CeO2 surfaces, and feasible engineering methods for the regulation of FLPs sites are presented. Furthermore, cases where typical small molecules (e.g., hydrogen, carbon dioxide, methane oxygen, etc.) are activated over FLPs are analyzed. Meanwhile, corresponding future challenges for the development of FLPs-centered theory are presented. The insights presented in this paper may contribute to the theories of FLPs, which can potentially provide inspiration for the development of broader environment- and energy-related catalysis involving small molecule activation.

Spinel Nanostructures for the Hydrogenation of CO2 to Methanol and Hydrocarbon Chemicals

Composite oxides have been widely applied in the hydrogenation of CO/CO2 to methanol or as the component of bifunctional oxide-zeolite for the synthesis of hydrocarbon chemicals. However, it is still challenging to disentangle the stepwise formation mechanism of CH3OH at working conditions and selectively convert CO2 to hydrocarbon chemicals with narrow distribution. Here, we investigate the reaction network of the hydrogenation of CO2 to methanol over a series of spinel oxides (AB2O4), among which the Zn-based nanostructures offer superior performance in methanol synthesis. Through a series of (quasi) in situ spectroscopic characterizations, we evidence that the dissociation of H2 tends to follow a heterolytic pathway and that hydrogenation ability can be regulated by the combination of Zn with Ga or Al. The coordinatively unsaturated metal sites over ZnAl2Ox and ZnGa2Ox originating from oxygen vacancies (OVs) are evidenced to be responsible for the dissociative adsorption and activation of CO2. The evolution of the reaction intermediates, including both carbonaceous and hydrogen species at high temperatures and pressures over the spinel oxides, has been experimentally elaborated at the atomic level. With the integration of a series of zeolites or zeotypes, high selectivities of hydrocarbon chemicals with narrow distributions can be directly produced from CO2 and H2, offering a promising route for CO2 utilization.

Heterogeneous MoS2 Nanosheets on Porous TiO2 Nanofibers toward Fast and Reversible Sodium-Ion Storage

2D layered molybdenum disulfide (MoS2) has garnered considerable attention as an attractive electrode material in sodium-ion batteries (SIBs), but sluggish mass transfer kinetic and capacity fading make it suffer from inferior cycle capability. Herein, hierarchical MoS2 nanosheets decorated porous TiO2 nanofibers (MoS2 NSs@TiO2 NFs) with rich oxygen vacancies are engineered by microemulsion electrospinning method and subsequent hydrothermal/heat treatment. The MoS2 NSs@TiO2 NFs improves ion/electron transport kinetic and long-term cycling performance through distinctive porous structure and heterogeneous component. Consequently, the electrode exhibits excellent long-term Na storage capacity (298.4 mAh g-1 at 5 A g-1 over 1100 cycles and 235.6 mAh g-1 at 10 A g-1 over 7200 cycles). Employing Na3V2(PO4)3 as cathode, the full cell maintains a desirable capacity of 269.6 mAh g-1 over 700 cycles at 1.0 A g-1. The stepwise intercalation-conversion and insertion/extraction endows outstanding Na+ storage performance, which yields valuable insight into the advancement of fast-charging and long-cycle life SIBs anode materials.

Highly Active and Sintering-Resistant Pt Clusters Supported on FeOx-Hydroxyapatite Achieved by Tailoring Strong Metal-Support Interactions

The catalytic performance of supported metal catalysts is closely related to their structure. While Pt-based catalysts are widely used in many catalytic reactions because of their exceptional intrinsic activity, they tend to deactivate in high-temperature reactions, requiring a tedious and expensive regeneration process. The strong metal-support interaction (SMSI) is a promising strategy to improve the stability of supported metal nanoparticles, but often at the price of the activity due to either the coverage of the active sites by support overlay and/or the too-strong metal-support bonding. Herein, we newly constructed a supported Pt cluster catalyst by introducing FeOx into hydroxyapatite (HAP) support to fine-tune the SMSIs. The catalyst exhibited not only high catalytic activity but also sintering resistance, without deactivation in a 100 h test for catalytic CO oxidation. Detailed characterizations reveal that FeOx introduced into HAP weaken the strong covalent metal-support interaction (CMSI) between Pt and FeOx while simultaneously inhibiting the oxidative strong metal-support interaction (OMSI) between Pt and HAP, giving rise to both high activity and thermal stability of the supported Pt clusters.

Modularization of Regional Electronic Structure over Defect-Rich CeO2 Rods for Enhancing Photogenerated Charge Transfer and CO2 Activation

Oxygen vacancy (OV) engineering has been widely applied in different types of metal oxide-based photocatalytic reactions. Our study has shown that the redistributed OVs resulting from voids in CeO2 rods lead to significant differences in the band structure in space. The flat energy band within the highly crystallized bulk region hinders the recombination of photogenerated carrier pairs during the transfer process. The downward curved energy band in the surface region enhances the activation of the absorbents. Therefore, the localization of the band structure through crystal structure regionalization renders V-CeO2 capable of achieving efficient utilization of photogenerated carriers. Practically, the V-CeO2 rod shows a remarkable turnover number of 190.58 μmol g-1 h-1 in CO2 photoreduction, which is ∼9.4 times higher than that of D-CeO2 (20.46 μmol g-1 h-1). The designed modularization structure in our work is expected to provide important inspiration and guidance in coordinating the kinetic behavior of carriers in OV defect-rich photocatalysts.

Oxygen vacancy chemistry in oxide cathodes

Secondary batteries are a core technology for clean energy storage and conversion systems, to reduce environmental pollution and alleviate the energy crisis. Oxide cathodes play a vital role in revolutionizing battery technology due to their high capacity and voltage for oxide-based batteries. However, oxygen vacancies (OVs) are an essential type of defect that exist predominantly in both the bulk and surface regions of transition metal (TM) oxide batteries, and have a crucial impact on battery performance. This paper reviews previous studies from the past few decades that have investigated the intrinsic and anionic redox-mediated OVs in the field of secondary batteries. We focus on discussing the formation and evolution of these OVs from both thermodynamic and kinetic perspectives, as well as their impact on the thermodynamic and kinetic properties of oxide cathodes. Finally, we offer insights into the utilization of OVs to enhance the energy density and lifespan of batteries. We expect that this review will advance our understanding of the role of OVs and subsequently boost the development of high-performance electrode materials for next-generation energy storage devices.

Photochemical tuning of dynamic defects for high-performance atomically dispersed catalysts

Developing active and stable atomically dispersed catalysts is challenging because of weak non-specific interactions between catalytically active metal atoms and supports. Here we demonstrate a general method for synthesizing atomically dispersed catalysts via photochemical defect tuning for controlling oxygen-vacancy dynamics, which can induce specific metal-support interactions. The developed synthesis method offers metal-dynamically stabilized atomic catalysts, and it can be applied to reducible metal oxides, including TiO2, ZnO and CeO2, containing various catalytically active transition metals, including Pt, Ir and Cu. The optimized Pt-DSA/TiO2 shows unprecedentedly high photocatalytic hydrogen evolution activity, producing 164 mmol g-1 h-1 with a turnover frequency of 1.27 s-1. Furthermore, it generates 42.2 mmol gsub-1 of hydrogen via a non-recyclable-plastic-photoreforming process, achieving a total conversion of 98%; this offers a promising solution for mitigating plastic waste and simultaneously producing valuable energy sources.

Way to a Library of Ti-Series Oxide Nanofiber Sponges that are Highly Stretchable, Compressible, and Bendable

Ti-series oxide ceramics in the form of aerogels, such as TiO2, SrTiO3, BaTiO3, and CaCu3Ti4O12, hold tremendous potential as functional materials owing to their excellent optical, dielectric, and catalytic properties. Unfortunately, these inorganic aerogels are usually brittle and prone to pulverization owing to weak inter-particulate interactions, resulting in restricted application performance and serious health risks. Herein, a novel strategy is reported to synthesize an elastic form of an aerogel-like, highly porous structure, in which activity-switchable Ti-series oxide sols transform from the metastable state to the active state during electrospinning, resulting in condensation and solidification at the whipping stage to obtain curled nanofibers. These curled nanofibers are further entangled when flying in the air to form a physically interlocked, elastic network mimicking the microstructure of high-elasticity hydrogels. This strategy provides a library of Ti-series oxide nanofiber sponges with unprecedented stretchability, compressibility, and bendability, possessing extensive opportunities for greener, safer, and broader applications as integrated or wearable functional devices. As a proof-of-concept demonstration, a new, elastic form of TiO2, composed of both "white" and "black" TiO2 nanofiber sponges, is constructed as spontaneous air-conditioning textiles in smart clothing, buildings, and vehicles, with unique bidirectional regulation of radiative cooling in summer and solar heating in winter.

Boosting Piezocatalytic Performance of BaTiO3 by Tuning Defects at Room Temperature

Defect engineering constitutes a widely-employed method of adjusting the electronic structure and properties of oxide materials. However, controlling defects at room temperature remains a significant challenge due to the considerable thermal stability of oxide materials. In this work, a facile room-temperature lithium reduction strategy is utilized to implant oxide defects into perovskite BaTiO3 (BTO) nanoparticles to enhance piezocatalytic properties. As a potential application, the piezocatalytic performance of defective BTO is examined. The reaction rate constant increases up to 0.1721 min-1, representing an approximate fourfold enhancement over pristine BTO. The effect of oxygen vacancies on piezocatalytic performance is discussed in detail. This work gives us a deeper understanding of vibration catalysis and provides a promising strategy for designing efficient multi-field catalytic systems in the future.

Synergistic Effect of Oxygen Vacancy and High Porosity of Nano MIL-125(Ti) for Enhanced Photocatalytic Nitrogen Fixation

This work reports that a low-temperature thermal calcination strategy was adopted to modulate the electronic structure and attain an abundance of surface-active sites while maintaining the crystal morphology. All the experiments demonstrate that the new photocatalyst nano MIL-125(Ti)-250 obtained by thermal calcination strategy has abundant Ti3+ induced by oxygen vacancies and high specific surface area. This facilitates the adsorption and activation of N2 molecules on the active sites in the photocatalytic nitrogen fixation. The photocatalytic NH3 yield over MIL-125(Ti)-250 is enhanced to 156.9 μmol g-1  h-1 , over twice higher than that of the parent MIL-125(Ti) (76.2 μmol g-1  h-1 ). Combined with density function theory (DFT), it shows that the N2 adsorption pattern on the active sites tends to be from "end-on" to "side-on" mode, which is thermodynamically favourable. Moreover, the electrochemical tests demonstrate that the high atomic ratio of Ti3+ /Ti4+ can enhance carrier separation, which also promotes the efficiency of photocatalytic N2 fixation. This work may offer new insights into the design of innovative photocatalysts for various chemical reduction reactions.

Characteristics and catalytic behavior of Ru-Sn bimetallic catalysts for TMCB hydrogenation to CBDO

A series of Ru-Sn/γ-Al2O3 catalysts were prepared by the immersion method for tetramethylcyclobutane-1,3-dione (TMCB) hydrogenation to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO). The effect of the preparation method and reaction technology on TMCB hydrogenation activity was discussed. The catalysts were analyzed by means of XRD, BET, H2-TPR, XPS, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and it was found that the synthesized Ru was distributed on the surface of the carrier in the form of nanoparticles, showing a good catalytic effect. The results showed that when Ru loading was fixed at 5%, Sn was used as an auxiliary agent, and Ru/Sn = 1 : 1 as the catalyst, the reaction conditions were 120 °C, 4 MPa, and 1 h, and the catalytic hydrogenation effect of TMCB on CBDO was the best. The selectivity was as high as 73.5%, and the cis-trans ratio was 1.11. It may be the strong interaction between Ru and Sn under this ratio condition, which leads to the largest number of nano-active centers of elemental Ru. Finally, the reaction mechanism of TMCB hydrogenation to CBDO is discussed.

N-doped carbon sheets supported P-Fe3O4-MoO2 for freshwater and seawater electrolysis

Electric-driven freshwater/seawater splitting is an attractive and sustainable route to realize the generation of H2 and O2. Molybdenum-based oxides exhibit poor activity toward freshwater/seawater electrolysis. Herein, we adjusted the electronic structure of MoO2 by constructing N-doped carbon sheets supported P-Fe3O4-MoO2 nanosheets (P-Fe3O4-MoO2/NC). P-Fe3O4-MoO2/N-doped carbon sheets were precisely prepared by pyrolysis of Schiff base Fe complex and MoO3 nanosheets through phosphorization. Benefiting from the unique structures of the samples, it required 119/145 mV to drive freshwater/seawater reduction reaction at 10 mA/cm2. P-Fe3O4-MoO2/NC catalysts exhibited superior freshwater/seawater oxidation reactivity with 180/189 mV at 10 mA/cm2 compared with commercial RuO2. The low cell voltages for P-Fe3O4-MoO2/NC were 1.47 and 1.59 V towards freshwater and seawater electrolysis, respectively. Our work might shed light on the structural modulation of Mo-based oxides for enhancing freshwater and seawater electrolysis activity.

A new Mn-based layered cathode with enlarged interlayer spacing for potassium ion batteries

Layered Mn-based cathode (KxMnO2) has attracted wide attention for potassium ion batteries (PIBs) because of its high specific capacity and energy density. However, the structure and capacity of KxMnO2 cathode are constantly degraded during the cycling due to the strong Jahn-Teller effect of Mn3+ and huge ionic radius of K+. In this work, lithium ion and interlayer water were introduced into Mn layer and K layer in order to suppress the Jahn-Teller effect and expand interlayer spacing, respectively, thus obtaining new types of K0.4Mn1-xLixO2·0.33H2O cathode materials. The interlayer spacing of the K0.4MnO2 increased from 6.34 to 6.93 Å after the interlayer water insertion. X-ray photoelectron spectroscopy studies demonstrated that proper lithium doping can effectively control the ratio of Mn3+/Mn4+ and inhibit the Jahn-Teller effect. In-situ X-ray diffraction exhibited that lithium doping can inhibit the irreversible phase transition and improve the structural stability of materials during cycling. As a result, the optimal K0.4Mn0.9Li0.1O2·0.33H2O not only delivered a higher capacity retention of 84.04 % compared to the value of 28.09 % for K0.4MnO2·0.33H2O, but also maintained a greatly enhanced rate capability. This study provides a new opportunity for designing layered manganese-based cathode materials with high performance for PIBs.

Boosting Oxygen Evolution Performance of Nickel-Iron Layered Double Hydroxides by Controlling Oxygen Vacancies and Structural Disorder via n-Butyllithium Treatment

Nickel-iron-based layered double hydroxides (NiFe-LDHs) are promising catalysts for the oxygen evolution reaction (OER) because of their high activity, availability, and low cost. Defect engineering, particularly the formation of oxygen vacancies, can improve the catalytic activity of NiFe-LDHs. However, the controllable introduction of uniform oxygen vacancies remains challenging. Herein, an n-butyllithium treatment method is developed to tune oxygen vacancy defects and change the degree of amorphization in NiFe-LDHs via deep reduction, followed by partial oxidization at low temperatures. Interestingly, the Ni in the NiFe-LDHs is selectively reduced to the alloy state by n-butyllithium, whereas Fe is not. The different structural transformations of Ni and Fe during the treatment successfully produce an oxygen-defect-rich amorphous/crystalline electrocatalyst. Under optimal conditions, the treated NiFe-LDHs exhibit high OER activity with an overpotential of 223 mV at 10 mA cm-2 (68 mV lower than that of a commercial IrO2 electrocatalyst) and long-term stability. Notably, the n-butyllithium treatment can be applied to other electrocatalysts, such as CoFe-LDHs and IrO2 (treated IrO2 with an overpotential of 197 mV at 10 mA cm-2). This n-butyllithium reduction/partial oxidization treatment constitutes a novel top-down strategy for the controllable modification of metal oxide structures, with various energy-related applications.

Defect-poor BaSn(OH)6 enhanced charge separation for efficient photocatalytic degradation of toluene

Crystal defect is well-known to have a significant effect on the photocatalytic performance of semiconductors. Herein, defect-rich and -poor BaSn(OH)6 (BSOH-Sn and BSOH-Ba) photocatalysts were synthesized by exchanging the addition order of Ba and Sn. Results show that the defect-poor BSOH-Ba exhibited more efficient toluene degradation under ultraviolet (UV) light, which could attribute to the great suppression of photogenerated electron-hole (e--h+) pairs recombination by tuning the defect concentration. The low defect concentration in BSOH-Ba finally promotes the charge separation efficiency, the generation of reactive oxygen species (ROS), and the photocatalytic toluene degradation reactions. This work not only provides an effective way to inhibit the recombination of photogenerated carriers and improve the photocatalytic performance, but also promotes the understanding of defective perovskite-type hydroxide for more photoreactions.

2D/2D MgO/g-C3N4 S-scheme heterogeneous tight with Mg-N bonds for efficient photo-Fenton degradation: Enhancing both oxygen vacancy and charge migration

Construction of S-scheme heterojunction is an efficient strategy to enhance photocatalytic efficiency. Besides the retained redox ability, the wide work function gap and intimate interface contact are essential for efficient degradation. Nontoxic magnesium oxide (MgO) with two dimensional (2D) structures and high work function is a potential material for S-scheme photocatalysts. Herein, MgO was used to in-situ grown on graphitic carbon nitride (g-C3N4) for constructing the strongly connected MgO/g-C3N4 S-scheme photocatalyst with tight Mg-N bonds. Meanwhile, the presence of Mg-N bonds induces the formation of oxygen vacancy in MgO, which enhances the Fenton-like degradation. Furthermore, the Mg-N bond promotes the charge migration between MgO and g-C3N4. Consisting of the enhanced Fenton-like process and photocatalysis, the MgO/g-C3N4 shows a higher photo-Fenton degradation activity (80.01%) for degradation of organic pollutants (Rhodamine B, 100 mg L-1) in water, than g-C3N4 (28.46%) and MgO (55.64%). Therefore, the interfacial chemical bonds in heterojunction photocatalysts provide an efficient strategy for further enhancing the photocatalysis of S-scheme photocatalysts.

Self-Reconstruction of Sulfate-Terminated Copper Oxide Nanorods for Efficient and Stable 5-Hydroxymethylfurfural Electrooxidation

The electrochemical 5-hydroxymethylfurfural oxidation reaction (HMFOR) has been regarded as a viable alternative to sustainable biomass valorization. However, the transformation of the catalysts under harsh electrooxidation conditions remains controversial. Herein, we confirm the self-construction of cuprous sulfide nanosheets (Cu2S NSs) into sulfate-terminated copper oxide nanorods (CuO-SO42- NRs) during the first-cycle of the HMFOR, which achieves a near-quantitative synthesis of 2,5-furandicarboxylic acid (FDCA) with a >99.9% yield and faradaic efficiency without deactivation in 15 successive cycles. Electrochemical impedance spectroscopies confirm that the surface SO42- effectively reduces the onset potential for HMFOR, while in situ Raman spectroscopies identify a reversible transformation from CuII-O to CuIII-OOH in HMFOR. Furthermore, density functional theory calculations reveal that the surface SO42- weakens the Cu-OH bonds in CuOOH to promote the rate-determining step of its coupling with the C atom in HMF-H* resulting from HMF hydrogenation, which synergistically enhances the catalytic activity of CuO-SO42- NRs toward HMF-to-FDCA conversion.

Control of metal oxides' electronic conductivity through visual intercalation chemical reactions

Cation intercalation is an effective method to optimize the electronic structures of metal oxides, but tuning intercalation structure and conductivity by manipulating ion movement is difficult. Here, we report a visual topochemical synthesis strategy to control intercalation pathways and structures and realize the rapid synthesis of flexible conductive metal oxide films in one minute at room temperature. Using flexible TiO2 nanofiber films as the prototype, we design three charge-driven models to intercalate preset Li+-ions into the TiO2 lattice slowly (µm/s), rapidly (mm/s), or ultrafast (cm/s). The Li+-intercalation causes real-time color changes of the TiO2 films from white to blue and then black, corresponding to the structures of LixTiO2 and LixTiO2-δ, and the enhanced conductivity from 0 to 1 and 40 S/m. This work realizes large-scale and rapid synthesis of flexible TiO2 nanofiber films with tunable conductivity and is expected to extend the synthesis to other conductive metal oxide films.

Oxygen-Deficient Bioceramics: Combination of Diagnosis, Therapy, and Regeneration

The journey of ceramics in medicine has been synchronized with an evolution from the first generation-alumina, zirconia, etc.-to the third -3D scaffolds. There is an up-and-coming member called oxygen-deficient or colored bioceramics, which have recently found their way through biomedical applications. The oxygen vacancy steers the light absorption toward visible and near infrared regions, making the colored bioceramics multifunctional-therapeutic, diagnostic, and regenerative. Oxygen-deficient bioceramics are capable of turning light into heat and reactive oxygen species for photothermal and photodynamic therapies, respectively, and concomitantly yield infrared and photoacoustic images. Different types of oxygen-deficient bioceramics have been recently developed through various synthesis routes. Some of them like TiO2- x , MoO3- x , and WOx have been more investigated for biomedical applications, whereas the rest have yet to be scrutinized. The most prominent advantage of these bioceramics over the other biomaterials is their multifunctionality endowed with a change in the microstructure. There are some challenges ahead of this category discussed at the end of the present review. By shedding light on this recently born bioceramics subcategory, it is believed that the field will undergo a big step further as these platforms are naturally multifunctional.

Platinum Species on Oxygen Vacancy-Rich Titania for Efficient Basic Electrocatalytic Hydrogen Evolution

Oxygen vacancy-rich titania is a promising support for enhancing the hydrogen evolution reaction (HER). This work innovatively loaded Pt nanoparticles on oxygen vacancy-rich TiO2 (Pt/Vo-TiO2) in situ by using a photocatalytic device. The synthesis conditions are mild, do not require high temperatures and strong reducing agents, and can avoid the accumulation of platinum species. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectrometry (XAS) verified the synergistic effect of Pt species and oxygen vacancies on the progress of the reaction kinetics, where the Pt particles exposed by the in situ synthesis functioned as reaction sites in the electrocatalytic hydrogen evolution. Based on this, Pt/Vo-TiO2 exhibits excellent electrocatalytic performance with an overpotential of only 56 mV at a current density of 10 mA cm-2 and a Tafel slope of only 73.5 mV dec-1. This work provides a new strategy for designing highly efficient HER catalysts.

Oxygen Defect Engineering toward Zero-Strain V2O2.8@Porous Reticular Carbon for Ultrastable Potassium Storage

Potassium-ion batteries (KIBs) are promising candidates for large-scale energy storage devices due to their high energy density and low cost. However, the large potassium-ion radius leads to its sluggish diffusion kinetics during intercalation into the lattice of the electrode material, resulting in electrode pulverization and poor cycle stability. Herein, vanadium trioxide anodes with different oxygen vacancy concentrations (V2O2.9, V2O2.8, and V2O2.7 determined by the neutron diffraction) are developed for KIBs. The V2O2.8 anode is optimal and exhibits excellent potassium storage performance due to the realization of expanded interlayer spacing and efficient ion/electron transport. In situ X-ray diffraction indicates that V2O2.8 is a zero-strain anode with a volumetric strain of 0.28% during the charge/discharge process. Density functional theory calculations show that the impacts of oxygen defects are embodied in reducing the band gap, increasing electron transfer ability, and lowering the diffusion energy barriers for potassium ions. As a result, the electrode of nanosized V2O2.8 embedded in porous reticular carbon (V2O2.8@PRC) delivers high reversible capacity (362 mAh g-1 at 0.05 A g-1), ultralong cycling stability (98.8% capacity retention after 3000 cycles at 2 A g-1), and superior pouch-type full-cell performance (221 mAh g-1 at 0.05 A g-1). This work presents an oxygen defect engineering strategy for ultrastable KIBs.

Xylene Synthesis Through Tandem CO2 Hydrogenation and Toluene Methylation Over a Composite ZnZrO Zeolite Catalyst

Selective synthesis of specific value-added aromatics from CO2 hydrogenation is of paramount interest for mitigating energy and climate problems caused by CO2 emission. Herein, we report a highly active composite catalyst of ZnZrO and HZSM-5 (ZZO/Z5-SG) for xylene synthesis from CO2 hydrogenation via a coupling reaction in the presence of toluene, achieving a xylene selectivity of 86.5 % with CO2 conversion of 10.5 %. A remarkably high space time yield of xylene could reach 215 mg gcat -1  h-1 , surpassing most reported catalysts for CO2 hydrogenation. The enhanced performance of ZZO/Z5-SG could be due to high dispersion and abundant oxygen vacancies of the ZZO component for CO2 adsorption, more feasible hydrogen activation and transfer due to the close interaction between the two components, and enhanced stability of the formate intermediate. The consumption of methoxy and methanol from the deep hydrogenation of formate by introduced toluene also propels an oriented conversion of CO2 .

Catalyst characteristics of the composite catalyst of Ru-Sn and Pd for hydrogenation of terephthalic acid

1,4-Cyclohexanedimethanol (CHDM) is a premium polyester monomer. In this paper, a series of Ru- Sn/γ-Al2O3 and Pd/γ-Al2O3 bimetallic composite catalysts were prepared by the impregnation method. The effects of preparation conditions such as active components, preparation methods, and the ratio of Sn to Ru on the reaction activity of the catalysts were studied. The bimetallic composite catalysts show desirable properties including high surface area and high dispersion of active centers. Pd-based catalysts were found to be effective in the initial stage of benzene ring hydrogenation, while Ru-based catalysts were found effective in the subsequent stage of carboxyl group hydrogenation. The Ru-Sn bimetallic active center was predominantly located in the Ru-based catalysts. In addition, the effects of reaction parameters such as reaction temperature, pressure, and time on hydrogenation reactions were also examined. It was found that increasing reaction temperature had no significant effect on the conversion rate of PTA, but it did affect the yield of CHDM, initially increasing and then decreasing. Increasing the reaction pressure resulted in a gradual increase in the yield of CHDM, while the conversion rate of PTA remained unchanged. The composite catalyst with a Sn/Ru ratio of 0.5 demonstrated the best performance, achieving a CHDM conversion of 96.3% and a yield of 72.2%.

Nonstoichiometric Scandium Oxide Hybridized in N-Doped Porous Graphitic Carbon Promotes the Rate Capability of Lithium-Sulfur Batteries

Nonstoichiometric compounds are widely used in contemporary energy technologies due to their high surface polarity, tailored electronic structure, high electrical conductivity, and other enhanced properties. However, the preparation of such nonstoichiometric compounds can be complicated and, in some cases, uncontrollable and dangerous. Here, we report a "one-pot" strategy for synthesizing N-doped porous graphitic carbon that is hybridized with nonstoichiometric scandium oxide (denoted as ScO0.95@N-PGC) and show that the composite significantly promotes sulfur cathode kinetics in lithium-sulfur (Li-S) batteries. The synthesis of the ScO0.95@N-PGC composite entails heating a porous dry gel that consists of a C source (glucose), a N source (dicyandiamide), and a Sc source (Sc(NO3)3·H2O). Thermally decomposing the dicyandiamide creates a highly reductive atmosphere that simultaneously affords the hypoxic state of the ScO0.95 and dopes the carbon matrix with nitrogen. Density functional theory reveals the presence of oxygen vacancies that enable the ScO0.95 crystals to function as excellent electrical conductors, exhibit enhanced adsorption toward polysulfides, and accelerate the cathode reactions by lowering the corresponding activation energies. Moreover, Li-S cells prepared from the ScO0.95@N-PGC composite display a high specific capacity (1046 mA h g-1 at 0.5 C), an outstanding cycling stability (641 mA h g-1 after 1000 charge-discharge cycles at 0.5 C, a capacity decay of 0.038% per cycle), and a particularly outstanding rate capability (438 mA h g-1 at 8 C). The methodology described establishes a sustainable approach for synthesizing nonstoichiometric compounds while broadening their potential utility in a broad range of energy technologies.

Titanium Oxide Electrocatalytic Membrane Filtration: "Two Faces" of Oxygen Vacancies in Generation and Transformation of Reactive Oxygen Species

Oxygen vacancies are crucial to the production of reactive oxygen species (ROS) in the metal oxide electrocatalytic membrane (MOx EM) process. Here, using cathodic TiOx EM as a model, we thoroughly reveal the roles of oxygen vacancies in ROS generation and transformation. Oxygen vacancies significantly promote H2O2 and •OH production at low concentrations (increment <35%) but inhibit their production at high concentrations (increment >35%). Electrochemical analysis discloses that the enhancement of ROS production profits from the acceleration of charge transfer kinetics by both bulk and surface oxygen vacancies, whereas we attribute the decline in ROS production to the strong adsorption of ROS by surface oxygen vacancies. It is strongly supported by theoretical calculations that reveal the promoted adsorption of *OOH and *OH by oxygen vacancies, which intensifies the capture and scavenging of H2O2 and •OH. Moreover, the gradual increase of interaction time between ROS and oxygen vacancies (from ∼1 to ∼5 s) notably reduces the generation and transformation efficiency of ROS, further highlighting the detrimental impact of oxygen vacancies. In summary, oxygen vacancies show "two faces" toward ROS generation and transformation, acting as ROS promoters at low concentrations but inhibitors at high concentrations. A medium oxygen vacancy concentration is preferred for ROS production, thus causing impressive pollutant removal (>95% removal of bisphenol A within 1.2-1.5 s at 360-440 LMH). This study provides guidance on regulating ROS generation and transformation by manipulating the oxygen vacancy concentration to enhance the decontamination efficiency of MOx EMs.

Quantitative Contribution of Oxygen Vacancy Defects to Arsenate Immobilization on Hematite

Hematite is a common iron oxide in natural environments, which has been observed to influence the transport and fate of arsenate by its association with hematite. Although oxygen vacancies were demonstrated to exist in hematite, their contributions to the arsenate immobilization have not been quantified. In this study, hematite samples with tunable oxygen vacancy defect (OVD) concentrations were synthesized by treating defect-free hematite using different NaBH4 solutions. The vacancy defects were characterized by positron annihilation lifetime spectroscopy, Doppler broadening of annihilation radiation, extended X-ray absorption fine structure (EXAFS), thermogravimetric mass spectrometry (TG-MS), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS). The results revealed that oxygen vacancy was the primary defect type existing on the hematite surface. TG-MS combined with EPR analysis allowed quantification of OVD concentrations in hematite. Batch experiments revealed that OVDs had a positive effect on arsenate adsorption, which could be quantitatively described by a linear relationship between the OVD concentration (Cdef, mmol m-2) and the enhanced arsenate adsorption amount caused by defects (ΔQm, μmol m-2) (ΔQm = 20.94 Cdef, R2 = 0.9813). NH3-diffuse reflectance infrared Fourier transform (NH3-DRIFT) analysis and density functional theory (DFT) calculations demonstrated that OVDs in hematite were beneficial to the improvement in adsorption strength of surface-active sites, thus considerably promoting the immobilization of arsenate.

Molecular oxygen-assisted in defect-rich ZnO for catalytic depolymerization of polyethylene terephthalate

Polyethylene terephthalate (PET) is the most produced polyester plastic; its waste has a disruptive impact on the environment and ecosystem. Here, we report a catalytic depolymerization of PET into bis(2-hydroxyethyl) terephthalate (BHET) using molecule oxygen (O2)-assisted in defect-rich ZnO. At air, the PET conversion rate, the BHET yield, and the space-time yield are 3.5, 10.6, and 10.6 times higher than those in nitrogen, respectively. Combining structural characterization with the results of DFT calculations, we conclude that the (100) facet of defect-rich ZnO nanosheets conducive to the formation of reactive oxygen species (∗O2-) and Zn defect, promotes the PET breakage of the ester bond and thus complete the depolymerization processed. This approach demonstrates a sustainable route for PET depolymerization by molecule-assisted defect engineering.

High-Performance Electrocatalytic Reduction of Nitrite to Ammonia under Ambient Conditions on a FeP@TiO2 Nanoribbon Array

Electrochemical nitrite (NO2-) reduction is recognized as a promising strategy for synthesizing valuable ammonia (NH3) and degrading NO2- pollutants in wastewater. The six-electron process for the NO2- reduction reaction is complex and necessitates a highly selective and stable electrocatalyst for efficient conversion of NO2- to NH3. Herein, a FeP nanoparticle-decorated TiO2 nanoribbon array on a titanium plate (FeP@TiO2/TP) is proposed as an efficient catalyst for NH3 production under ambient conditions. In 0.1 M NaOH with 0.1 M NO2-, such a FeP@TiO2/TP affords a large NH3 yield of 346.6 μmol h-1 cm-2 and a high Faradaic efficiency of 97.1%. Additionally, it demonstrates excellent stability and durability during long-term cycling tests and electrolysis experiments.

Oxygen-deficient TiO2-x interlayer enabling Li-rich Mn-based layered oxide cathodes with enhanced reversible capacity and cyclability

The unique anion redox mechanism of Li-rich Mn-based layered oxide (LMLO) cathodes endows them with a higher specific capacity compared with conventional cathodes. However, the irreversible anion redox reactions can cause structural degradation and sluggish electrochemical kinetics in the cathode, resulting in a poor electrochemical performance in the batteries. Thus, to address these issues, a single-sided conductive oxygen-deficient TiO_2-x interlayer was applied on a commercial Celgard separator as a coating layer towards the LMLO cathode. After coating TiO_2-x, the initial coulombic efficiency (ICE) of the cathode increased from 92.1% to 95.8%, the capacity retention improved from 84.2% to 91.7% after 100 cycles, and the rate performance of the cathode was significantly enhanced from 91.3 mA h g^-1 to 203.9 mA h g^-1 at 5C. Operando differential electrochemical mass spectroscopy (DEMS) showed that the coating layer could restrain the release of oxygen in the battery, especially from the initial formation process. The X-ray photoelectron spectroscopy (XPS) results demonstrated that the favorable oxygen absorption by the TiO_2-x interlayer benefitted the suppression of side reactions and cathode structural evolution and favored the formation of a uniform cathode-electrolyte interphase on the LMLO cathode. This work provides an alternative path to address the issue of oxygen release in LMLO cathodes.

Novel ultrasensitive Raman assay method based on enzyme mimetics for ultra trace of H2O2

Enzyme mimetics have been widely applied on H₂O₂ assay, but it is still challenging and interesting to realize the sensitive detection for ultra-trace H₂O₂. Here, an ultrasensitive Raman assay method based on novel WO₃@IP6-Fe³⁺ enzyme mimetics with peroxidase-like activity was established. WO₃ microspheres (MSs) were found to have weak peroxidase-like activity, and the combination of IP6-Fe³⁺ and WO₃ can produce stronger activity. WO₃@IP6-Fe³⁺ MSs showed polyhedron-like structure, uniform size, and smooth surface. Although WO₃@IP6-Fe³⁺ enzyme mimetics have low catalytic efficiency and high absorbance background, the proposed Raman method can bypass the above problems. In Raman method, high concentration of WO₃@IP6-Fe³⁺ can be used to overcome low catalytic efficiency without high absorbance background. Moreover, 3,3',5,5'-tetramethylbenzidine oxide has prominent characteristic Raman peak at 1608 cm^-1, greatly improving the sensitivity and eliminating interference of impurities. Due to the high sensitivity and low background, Raman assay showed the ultra-low limit of detection (5.49 × 10^-15 M), which was 4-7 orders of magnitude lower than other detection methods. The ultrasensitive Raman assay not only provided the possibility for the enzyme mimetics-based detection of ultra-trace H₂O₂, but also enable the enzyme mimetics with low activity to be applied.

Hierarchical Hollow-TiO2@CdS/ZnS Hybrid for Solar-Driven CO2-Selective Conversion

Light-driven valorization conversion of CO₂ is an encouraging carbon-negative pathway that shifts energy-reliance from fossil fuels to renewables. Herein, a hierarchical urchin-like hollow-TiO₂@CdS/ZnS (HTO@CdS/ZnS) Z-scheme hybrid synthesized by an in situ self-assembly strategy presents superior photocatalytic CO₂-to-CO activity with nearly 100% selectivity. Specifically, benefitting from the reasonable architectural and interface design, as well as surface modification, this benchmarked visible-light-driven photocatalyst achieves a CO output of 62.2 μmol·h^-1 and a record apparent quantum yield of 6.54% with the Co(bpy)₃²⁺ (bpy = 2,2'-bipyridine) cocatalyst. It rivals all the incumbent selective photocatalytic conversion of CO₂ to CO in the CH₃CN/H₂O/TEOA reaction systems. Specifically, the addition of HTO and stabilized ZnS enables the photocatalyst to effectively upgrade optical and electrical performances, contributing to efficient light-harvesting and photogenerated carrier separation, as well as interfacial charge transfer. The tremendous enhancement of photocatalytic performance reveals the superiority of the Z-scheme heterojunction assembled from HTO and CdS/ZnS, featuring the inner electric field derived from the band bending of HTO@CdS/ZnS make CdS resistant to photocorrosion. This study allows access to inspire studies on rationally modeling and constructing diverse heterostructures for the storage and conversion of renewables and chemicals.

Hierarchical triphase diffusion photoelectrodes for photoelectrochemical gas/liquid flow conversion

Photoelectrochemical device is a versatile platform for achieving various chemical transformations with solar energy. However, a grand challenge, originating from mass and electron transfer of triphase-reagents/products in gas phase, water/electrolyte/products in liquid phase and catalyst/photoelectrode in solid phase, largely limits its practical application. Here, we report the simulation-guided development of hierarchical triphase diffusion photoelectrodes, to improve mass transfer and ensure electron transfer for photoelectrochemical gas/liquid flow conversion. Semiconductor nanocrystals are controllably integrated within electrospun nanofiber-derived mat, overcoming inherent brittleness of semiconductors. The mechanically strong skeleton of free-standing mat, together with satisfactory photon absorption, electrical conductivity and hierarchical pores, enables the design of triphase diffusion photoelectrodes. Such a design allows photoelectrochemical gas/liquid conversion to be performed continuously in a flow cell. As a proof of concept, 16.6- and 4.0-fold enhancements are achieved for the production rate and product selectivity of methane conversion, respectively, with remarkable durability.

A holistic review on the recent trends, advances, and challenges for high-precision room temperature liquefied petroleum gas sensors

Liquefied petroleum gas (LPG), which is mainly composed of hydrocarbons, such as propane and butane, is a flammable gas that is considered a clean source of energy. Currently, the overwhelming use of LPG as fuel in vehicles, domestic settings, and industry has led to several incidents and deaths globally due to leakage. As a result, the appropriate detection of LPG is vital; thus, gas-sensing devices that can monitor this gas rapidly and accurately at room temperature, are required. This work reviews the current advances in LPG gas sensors, which operate at room temperature. The influences of the synthesis methods and parameters, doping, and use of catalysts on the sensing performance are discussed. The formation of heterostructures made from semiconducting metal oxides, polymers, and graphene-based materials, which enhance the sensor selectivity and sensitivity, is also discussed. The future trends and challenges confronted in the advancement of LPG room temperature operational gas sensors, and critical ideas concerning the future evolution of LPG gas sensors, are deliberated. Additionally, the advancements in the next-generation gas sensors, such as the wireless detection of LPG leakage, self-powered sensors driven by triboelectric/piezoelectric mechanisms, and artificial intelligent systems are also reviewed. This review further focuses on the use of smartphones to circumvent the use of costly instruments and paves the way for cost-efficient and portable monitoring of LPG. Finally, the approach of utilizing the Internet of Things (IoT) to detect/monitor the leakage of LPG has also been discussed, which will provide better alerts to the users and thus minimize the effects of leakages.

Deciphering the photoactive species-directed antibacterial mechanism of bismuth oxychloride with modulated nanoscale thickness

As an environmentally benign disinfection strategy, photocatalytic bacterial inactivation using nanoparticles involves photogenerated reactive species that cause cellular oxidative stress. Rationalising the structural performance of photocatalysts for the practical uses such as wastewater treatment has attracted significant attention; however, the contribution of reactive species to their photocatalytic antibacterial activities at the molecular and transcriptomic levels remains unclear. In this study, nontoxic bismuth oxychloride (BiOCl) photocatalysts with different nanoscale thicknesses, including nanosheets (Ns, ∼5.4 nm), nanoplates (Np, ∼1.8 nm), and ultra-nanosheets (Uns, ∼1.1 nm), were synthesised under hydrothermal conditions. Among the three samples, BiOCl Uns exhibited the most effective photocatalytic degradation efficiency with the calculated apparent rate constant of 0.0294 min^-1, ∼4 times faster than that of Ns, whereas BiOCl Ns possessed the most pronounced bactericidal effect (5.4 log inactivation). Such findings indicate the distinct role of the photoactive species responsible for photocatalytic bacterial inactivation. Moreover, transcriptome analysis of Escherichia coli after photocatalytic treatment revealed that the underlying photocatalytic antibacterial mechanism at the genetic expression level involves cellular component biosynthesis, energy metabolism, and material transportation. Notably, the differences between BiOCl Ns and BiOCl Uns were significantly enriched in purine metabolism. Therefore, the cost-effective preparation of BiOCl nanosheets with nanoscale thickness-modulated photocatalytic antibacterial activity has remarkable potential for sustainable environmental and biomedical applications.

Interfacial molecular regulation of TiO2 for enhanced and stable cocatalyst-free photocatalytic hydrogen production

On the basis of the inherent property limitations of commercial P25-TiO₂, many surface interface modification methods have attracted substantial attention for further improving the photocatalytic properties. However, current strategies for designing and modifying efficient photocatalysts (which exhibit complicated manufacturing processes and harsh conditions) are not efficient for production that is low cost, is nontoxic, and exhibits good stability; and therefore restrict practical applications. Herein, a facile and reliable method is reported for in situ amine-containing silane coupling agent functionalization of commercial P25-TiO₂ by covalent surface modification for constructing a highly efficient photocatalyst. As a consequence, a high efficiency of H₂ evolution was achieved for TiO₂-SDA with 0.95 mmol h^-1 g^-1 (AQE ∼45.6 % at 365 nm) under solar light irradiation without a co-catalyst. The amination modification broadens the light absorption range of the photocatalyst, inhibits the binding of photogenerated carriers, and improves the photocatalytic efficiency; which was verified by photochemical properties and DFT theoretical calculations. This covalent modification method ensures the stability of the photocatalytic reaction. This work provides an approach for molecularly modified photocatalysts to improve photocatalytic performance by covalently modifying small molecules containing amine groups on the photocatalyst surface.

Crystallinity engineering for overcoming the activity-stability tradeoff of spinel oxide in Fenton-like catalysis

A precise modulation of heterogeneous catalysts in structural and surface properties promises the development of more sustainable advanced oxidation water purification technologies. However, while catalysts with superior decontamination activity and selectivity are already achievable, maintaining a long-term service life of such materials remains challenging. Here, we propose a crystallinity engineering strategy to break the activity-stability tradeoff of metal oxides in Fenton-like catalysis. The amorphous/crystalline cobalt-manganese spinel oxide (A/C-CoMnOx) provided highly active, hydroxyl group-rich surface, with moderate peroxymonosulfate (PMS)-binding affinity and charge transfer energy and strong pollutant adsorption, to trigger concerted radical and nonradical reactions for efficient pollutant mineralization, thereby alleviating the catalyst passivation by oxidation intermediate accumulation. Meanwhile, the surface-confined reactions, benefited from the enhanced adsorption of pollutants at A/C interface, rendered the A/C-CoMnOx/PMS system ultrahigh PMS utilization efficiency (82.2%) and unprecedented decontamination activity (rate constant of 1.48 min-1) surpassing almost all the state-of-the-art heterogeneous Fenton-like catalysts. The superior cyclic stability and environmental robustness of the system for real water treatment was also demonstrated. Our work unveils a critical role of material crystallinity in modulating the Fenton-like catalytic activity and pathways of metal oxides, which fundamentally improves our understanding of the structure-activity-selectivity relationships of heterogeneous catalysts and may inspire material design for more sustainable water purification application and beyond.

Metal-oxo Cluster Mediated Atomic Rh with High Accessibility for Efficient Hydrogen Evolution

Achieving single-atom catalysts (SACs) with high metal content and outstanding performance as well as robust stability is critically needed for clean and sustainable energy. However, most of the synthesized SACs are undesired on the loading content of the metal due to the anchored metals and the supports as well as the synthesizing methods. Herein, a Rh-SAC with high accessibility by loading it on the metal nodes of metal-porphyrin-based PCN MOFs (PCN-224) as supporting material is reported. Significantly, the PCN-Rh_15.9 /KB catalyst with a high Rh content of 15.9 wt% exhibits excellent hydrogen evolution activity with a low overpotential of 25 mV at a current density of 10 mA cm^-2 and a mass activity of 7.7 A mg^-1 _Rh at overpotential of 150 mV, which is much better than that of the commercial Rh/C. Various characterizations reveal the Rh species is stabilized by the metal nodes bearing -O/OH_x in MOFs, which is of importance for the high loading amount and the good activity. This work establishes an efficient approach to synthesize high content SACs on the nodes of MOFs for wide catalyst design.

Defect-Modified nano-BaTiO3 as a Sonosensitizer for Rapid and High-Efficiency Sonodynamic Sterilization

Multidrug-resistant bacteria caused by the unlimited overuse of antibiotics pose a great challenge to global health. An antibacterial method based on reactive oxygen species (ROS) is one of the effective strategies without inducing bacterial resistance. Owing to the ability of generating ROS, piezocatalytic material-mediated sonodynamic therapy (SDT) has drawn much attention. However, its major challenge is the low ROS generation efficiency in the piezocatalytic process due to the poor charge carrier concentration of piezoelectric materials. Vacancy engineering can regulate the charge density and largely promote ROS generation under ultrasound (US) irradiation. Herein, a US-responsive self-doped barium titanate with controlled oxygen vacancy (Vo) concentrations was successfully synthesized through a facile thermal reduction treatment at different temperatures (i.e., 350, 400, and 450 °C), and the corresponding samples were named as BTO-350, BTO-400, and BTO-450, respectively. Then, the effect of Vo concentrations on ROS generation efficiency during the piezocatalytic process was systematically studied. And BTO-400 was found to possess the highest piezocatalytic activity and excellent sonodynamic antibacterial performance against Escherichia coli and Staphylococcus aureus. Furthermore, its antibacterial mechanism was confirmed that the ROS generated under US could damage bacterial cell membrane and cause considerable leakage of cytoplasmic components and irreversible death of bacteria. Notably, the in vivo results illustrated that the BTO-400 could serve as an effective antibacterial agent and accelerate skin healing via SDT therapy. In all, the Vo defect-modified nano-BaTiO₃ has a noticeable potential to induce a rapid and efficient sterilization as well as skin tissue repair by SDT.

Magnesium: properties and rich chemistry for new material synthesis and energy applications

Magnesium (Mg) has many unique properties suitable for applications in the fields of energy conversion and storage. These fields presently rely on noble metals for efficient performance. However, among other challenges, noble metals have low natural abundance, which undermines their sustainability. Mg has a high negative standard reduction potential and a unique crystal structure, and its low melting point at 650 °C makes it a good candidate to replace or supplement numerous other metals in various energy applications. These attractive features are particularly helpful for improving the properties and limits of materials in energy systems. However, knowledge of Mg and its practical uses is still limited, despite recent studies which have reported Mg's key roles in synthesizing new structures and modifying the chemical properties of materials. At present, information about Mg chemistry has been rather scattered without any organized report. The present review highlights the chemistry of Mg and its uses in energy applications such as electrocatalysis, photocatalysis, and secondary batteries, among others. Future perspectives on the development of Mg-based materials are further discussed to identify the challenges that need to be addressed.

Spinel-Derived Formation and Amorphization of Bimetallic Oxyhydroxides for Efficient Electrocatalytic Biomass Oxidation

Replacing the oxygen evolution reaction (OER) with water-assisted oxidation of organic molecules represents a promising approach for achieving sustainable electrochemical biomass utilization. Among numerous OER catalysts, spinels have received substantial attention due to their manifold compositions and valence states, yet their application in biomass conversions remains rare. Herein, a series of spinels were investigated for the selective electrooxidation of furfural and 5-hydroxymethylfurfural, two model substrates for versatile value-added chemical products. Spinel sulfides universally exhibit superior catalytic performance compared to that of spinel oxides, and further investigations show that the replacement of oxygen with sulfur led to the complete phase transition of spinel sulfides into amorphous bimetallic oxyhydroxides during electrochemical activation, serving as the active species. Excellent values of conversion rate (100%), selectivity (100%), faradaic efficiency (>95%), and stability were achieved via sulfide-derived amorphous CuCo-oxyhydroxide. Furthermore, a volcano-like correlation was established between their BEOR and OER activities based on an OER-assisted organic oxidation mechanism.