Enhanced Photoelectrocatalytic Activities for CH 3 OH‐to‐HCHO Conversion on Fe 2 O 3 /MoO 3 : Fe‐O‐Mo Covalency Dominates the Intrinsic Activity

Boosting the Zn2+ storage capacity of MoO3 nanoribbons by modulating the electrons spin states of Mo via Ni doping

Aqueous zinc-ion batteries (AZIBs) have received considerable potential for their affordability and high reliability. Among potential cathodes, α-MoO3 stands out due to its layered structure aligned with the (010) plane, offering extensive ionic insertion channels for enhanced charge storage. However, its limited electrochemical activity and poor Zn2+ transport kinetics present significant challenges for its deployment in energy storage devices. To overcome these limitations, we introduce a new strategy by doping α-MoO3 with Ni (Ni-MoO3), tuning the electron spin states of Mo. Thus modification can activate the reactivity of Ni-MoO3 towards Zn2+ storage and weaken the interaction between Ni-MoO3 and intercalated Zn2+, thereby accelerating the Zn2+ transport and storage. Consequently, the electrochemical properties of Ni-MoO3 significantly surpass those of pure MoO3, demonstrating a specific capacity of 258 mAh g-1 at 1 A g-1 and outstanding rate performance (120 mAh g-1 at 10 A g-1). After 1000 cycles at 8 A g-1, it retains 76 % of the initial capacity, with an energy density of 154.4 Wh kg-1 and a power density of 11.2 kW kg-1. This work proves that the modulation of electron spin states in cathode materials via metal ion doping can effectively boost their capacity and cycling durability.

Efficient photoanode with a MoS2/TiO2/Au nanoparticle heterostructure for ultraviolet-visible photoelectrocatalysis

Green energy technology is generally becoming one of hot issues that need to be solved due to the adverse effects on the environment of fossil fuels. One of the strategies being studied and developed by theorists and experimentalists is the use of photoelectrochemical (PEC) cells, which are emerging as a candidate to produce hydrogen from water splitting. However, creating photoelectrodes that meet the requirements for PEC water splitting has emerged as the primary obstacle in bringing this technology to commercial fruition. Here, we construct a heterostructure, which consists of MoS2/TiO2/Au nanoparticles (NPs) to overcome the drawbacks of the photoanode. Owing to the dependence on charge transfer, the bandgap of MoS2/TiO2and the utilization the Au NPs as a stimulant for charges separation of TiO2by localized surface plasmon resonances effect as well as the increase of hot electron injection to cathode, leading to photocatalytic activities are improved. The results have recorded a significant increase in the photocurrent density from 2.3μAcm-2of TiO2to approximately 16.3μAcm-2of MoS2/TiO2/Au NPs. This work unveils a promising route to enhance the visible light adsorption and charge transfer in photo-electrode of the PEC cells by combining two-dimensional materials with metal NPs.

Selective Oxidation of Alcohol to Valuable Aldehydes Using Water as a Promoter in a Photoelectrochemical Cell

Artificial photoelectrochemistry (PEC) has emerged as a promising and efficient technology for the sustainable conversion of solar energy into chemicals. In this study, we present a refined PEC process that enables the highly selective and stable production of piperonal and other valuable aldehydes through the oxidation of the corresponding alcohols. By employing Fe2O3 or TiO2 as the photoanode material and 2,2,6,6-tetramethylpiperidinooxy (TEMPO) as a redox mediator in an H2O/acetonitrile solution, we achieve 100% selectivity and a >95% Faradaic efficiency for piperonal production from piperonyl alcohol (PA) oxidation. Remarkably, we reveal the enhancing effect on the PA oxidation reactivity of appropriate-amount water in the solvent as it plays a crucial role in inhibiting the photoelectron-hole recombination efficiency and facilitating charge transfer. Mechanistic analysis suggests that TEMPO-mediated PA oxidation involves the formation of •O2- radicals by the reduction of oxygen on the cathode, resulting in water as the sole byproduct. Furthermore, our PEC oxidation system exhibits applications on the 100%-selective production of various conjugated aldehydes, including 4-anisaldehyde, cuminaldehyde, and the vitamin B6 derivative. By implementing a TiO2//Fe2O3 dual-photoanode system, we achieve an enhanced piperonal production rate of 31.2 μmol h-1 cm-2 at 1.0 V vs Ag/Ag+ and demonstrate its stability over a 102 h cyclic test, ensuring near-quantitative yield. This research illuminates the potential of the PEC strategy as a generally applicable method for the efficient production of high-value aldehydes.

Stabilizing BiVO4 Photoanode in Bicarbonate Electrolyte for Efficient Photoelectrocatalytic Alcohol Oxidation

In order to expand the application of bismuth vanadate (BiVO4) to the field of photoelectrochemistry, researchers have explored the potential of BiVO4 in catalyzing or degrading organic substances, potentially presenting a green and eco-friendly solution. A study was conducted to investigate the impact of electrolytes on the photocatalysis of benzyl alcohol by BiVO4. The research discovered that, in an acetonitrile electrolyte (pH 9) with sodium bicarbonate, BiVO4 catalyzed benzyl alcohol by introducing saturated V5+. This innovation addressed the issue of benzyl alcohol being susceptible to catalysis in an alkaline setting, as V5+ was prone to dissolution in pH 9 on BiVO4. The concern of the photocorrosion of BiVO4 was mitigated through two approaches. Firstly, the incorporation of a non-aqueous medium inhibited the formation of active material intermediates, reducing the susceptibility of the electrode surface to photocorrosion. Secondly, the presence of saturated V5+ further deterred the leaching of V5+. Concurrently, the production of carbonate radicals by bicarbonate played a vital role in catalyzing benzyl alcohol. The results show that, in this system, BiVO4 has the potential to oxidize benzyl alcohol by photocatalysis.

Limiting Interfacial Free Water and Proton Concentration by Hydrogel Electrolytes for Stable MoO3 Anode in a Proton Battery

Aqueous rechargeable proton batteries are attractive due to the small ionic radius, light mass, and ultrafast diffusion kinetics of proton as charge carriers. However, the commonly used acidic electrolyte is usually very corrosive to the electrode material, which seriously affects the cycle life of the battery. Here, it is proposed that decreasing water activity and limiting proton concentration can effectively prevent side reactions of the MoO3 anode such as corrosion and hydrogen precipitation by using a lean-water hydrogel electrolyte. The as-prepared polyacrylamide (PAAM)-poly2-acrylamide-2-methylpropanesulfonic acid (PAMPS)/MnSO4 (PPM) hydrogel electrolyte not only has abundant hydrophilic groups that can form hydrogen bonds with free water and inhibit solvent-electrode interaction, but also has fixed anions that can maintain a certain interaction with protons. The assembled MoO3||MnO2 full battery can stably cycle over 500 times for ≈350 h with an unprecedented capacity retention of 100% even at a low current density of 0.5 A g-1. This work gives a hint that limiting free water as well as proton concentration is important for the design of electrolytes or interfaces in aqueous proton batteries.

Selective CO2 -to-Syngas Conversion Enabled by Bimetallic Gold/Zinc Sites in Partially Reduced Gold/Zinc Oxide Arrays

Electrocatalytic CO2 -to-syngas (gaseous mixture of CO and H2 ) is a promising way to curb excessive CO2 emission and the greenhouse gas effect. Herein, we present a bimetallic AuZn@ZnO (AuZn/ZnO) catalyst with high efficiency and durability for the electrocatalytic reduction of CO2 and H2 O, which enables a high Faradaic efficiency of 66.4 % for CO and 26.5 % for H2 and 3 h stability of CO2 -to-syngas at -0.9 V vs. the reversible hydrogen electrode (RHE). The CO/H2 ratios show a wide range from 0.25 to 2.50 over a narrow potential window (-0.7 V to -1.1 V vs. RHE). In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy combined with density functional theory calculations reveals that the bimetallic synergistic effect between Au and Zn sites lowers the activation energy barrier of CO2 molecules and facilitates electronic transfer, further highlighting the potential to control CO/H2 ratios for efficient syngas production using the coexisting Au sites and Zn sites.

Corner-Sharing Tetrahedrally Coordinated W-V Dual Active Sites on Cu2 V2 O7 for Photoelectrochemical Water Oxidation

The sluggish four-electron oxygen evolving reaction is one of the key limitations of photoelectrochemical water decomposition. Optimizing the binding of active sites to oxygen in water and promoting the conversion of *O to *OOH are the key to enhancing oxygen evolution reaction. In this work, W-doped Cu2 V2 O7 (CVO) constructs corner-sharing tetrahedrally coordinated W-V dual active sites to induce the generation of electron deficiency active centers, promote the adsorption of ─OH, and accelerate the transformation of *O to *OOH for water splitting. The photocurrent obtained by the W-modified CVO photoanode is 0.97 mA cm-2 at 1.23 V versus RHE, which is much superior to that of the reported CVO. Experimental and theoretical results show that the excellent catalytic performance may be attributed to the formation of synergistic dual active sites between W and V atoms, and the introduction of W ions reduces the charge migration distance and prolongs the lifetime of photogenerated carriers. Meanwhile, the electronic structure in the center of the d-band is modulated, which leads to the redistribution of the electron density in CVO and lowers the energy barrier for the conversion of the rate-limiting step *O to *OOH.

Organic Upgrading through Photoelectrochemical Reactions: Toward Higher Profits

Aqueous photoelectrochemical (PEC) cells have long been considered a promising technology to convert solar energy into hydrogen. However, the solar-to-H2 (STH) efficiency and cost-effectiveness of PEC water splitting are significantly limited by sluggish oxygen evolution reaction (OER) kinetics and the low economic value of the produced O2 , hindering the practical commercialization of PEC cells. Recently, organic upgrading PEC reactions, especially for alternative OERs, have received tremendous attention, which improves not only the STH efficiency but also the economic effectiveness of the overall reaction. In this review, PEC reaction fundamentals and reactant-product cost analysis of organic upgrading reactions are briefly reviewed, recent advances made in organic upgrading reactions, which are categorized by their reactant substrates, such as methanol, ethanol, glycol, glycerol, and complex hydrocarbons, are then summarized and discussed. Finally, the current status, further outlooks, and challenges toward industrial applications are discussed.

Fast Interfacial Carrier Dynamics Modulated by Bidirectional Charge Transport Channels in ZnIn2 S4 -based Composite Photoanodes Probed by Scanning Photoelectrochemical Microscopy

Limited charge separation/transport efficiency remains the primary obstacle of achieving satisfying photoelectrochemical (PEC) water splitting performance. Therefore, it is essential to develop diverse interfacial engineering strategies to mitigate charge recombination. Despite obvious progress having been made, most works only considered a single-side modulation in either the electrons of conduction band or the holes of valence band in a semiconductor photoanode, leading to a limited PEC performance enhancement. Beyond this conventional thinking, we developed a novel coupling modification strategy to achieve a composite electrode with bidirectional carrier transport for a better charge separation, in which Ti2 C3 Tx MXene quantum dots (MQDs) and α-Fe2 O3 nanodots (FO) are anchored on the surface of ZnIn2 S4 (ZIS) nanoplates, resulting in markedly improved PEC water splitting of pure ZIS photoanode. Systematic studies indicated that the bidirectional charge transfer pathways were stimulated due to MQDs as "electron extractor" and S-O bonds as carriers transport channels, which synergistically favors significantly enhanced charge separation. The enhanced kinetic behavior at the FO/MQDs/ZIS interfaces was systematically and quantitatively evaluated by a series of methods, especially scanning photoelectrochemical microscopy. This work may deepen our understanding of interfacial charge separation, and provide valuable guidance for the rational design and fabrication of high-performance composite electrodes.

Direct Electrocatalytic Methanol Oxidation on MoO3/Ni(OH)2: Exploiting Synergetic Effect of Adjacent Mo and Ni

Ni-based materials have been widely investigated as methanol oxidation reaction (MOR) catalysts. The formation of NiOOH and its reduction to Ni(OH)2 are generally regarded as essential steps for methanol oxidation. However, in such an indirect route, the efficiency of proton coupled electron transfer is fundamentally limited by the rate of transition from Ni(OH)2 to NiOOH back and forth. Herein we demonstrate a direct MOR pathway on MoO3/Ni(OH)2 without the formation of a NiOOH mediator. The MoO3/Ni(OH)2 exhibits a benchmark electrocatalytic MOR current density of 1000 mA cm-2 at 1.52 V vs. RHE with a nearly 100% faradic efficiency, outperforming all the state of art MOR electrocatalysts. In-situ Raman spectroscopy confirms that NiOOH is not formed during the electrocatalytic MOR process on the MoO3/Ni(OH)2. Density functional theory calculations suggest that Ni2+ in MoO3/Ni(OH)2 serves as the methanol adsorption site while the doped Mo6+ plays a key role in capturing the deprotonated H·. Benefiting from the Mo-Ni synergistic effect, the energy barrier of the CH2O* → CHO* + H* process is significantly reduced, avoiding the NiOOH formation and leading to the direct MOR. Our research unravels a direct electrochemical MOR pathway that does not rely on NiOOH formation and provides a facile strategy of regulating the intermediate process barrier for MOR.

Fabricating a type II heterojunction by growing lead-free perovskite Cs2AgBiBr6in situ on graphite-like g-C3N4 nanosheets for enhanced photocatalytic CO2 reduction

Perovskite-based photocatalysts have received significant attention for converting CO2 into fuels, such as CO, CH4 or long alkyl chains. However, the use of these catalysts is plagued by several limitations, such as poor stability, lead toxicity, and inadequate conversion efficiency due to the rapid recombination of carriers. Herein, a g-C3N4@Cs2AgBiBr6 (CABB) type II heterojunction photocatalyst has been prepared by growing lead-free CABB nanocrystals (10-14 nm) on the graphite-like carbon nitride (g-C3N4) nanosheet using the in situ crystallization method. The resulting nanocomposite, g-C3N4@CABB, demonstrated an efficient charge transfer pathway via a typical type II heterojunction. With formation rates of 10.30 μmol g-1 h-1 for CO and 0.88 μmol g-1 h-1 for CH4 under visible light irradiation, the nanocomposite exhibited enhanced photocatalytic efficiency in CO2 reduction compared to CABB and g-C3N4. The improved photocatalytic performance of the g-C3N4@CABB nanocomposite was attributed to the fabricated type II heterojunction, which boosted the interfacial charge transfer from g-C3N4 to CABB. This work will inspire the design of heterojunction-based photocatalysts and increase the fundamental understanding of perovskite-based catalysts in the CO2 photoreduction process.

In Situ Fabrication of a 2D/2D MXene/CN Heterojunction for Photothermally Assisted Photocatalytic Sterilization under Visible Light Irradiation

Constructing an efficient visible light-responsive antibacterial material for water treatment remains a principal goal yet is a huge challenge. Herein, a 2D/2D heterojunction composite with robust interfacial contact, named MXene/CN (MCN), was controllably fabricated by using a urea molecule intercalated into MXene following an in situ calcination method, which can realize the rapid separation and migration of photogenerated carriers under visible light irradiation and significantly improve the carrier concentration of the MXene surface, thus generating more reactive oxygen species. The generation of heat induced by MXene could also increase photogenic electron activity to facilitate the photocatalytic reaction using in situ time-resolved photoluminescence characterization. The visible light-activated germicide exhibits a sterilization efficacy against Escherichia coli of 99.70%, higher than those of pure CN (60.21%) and MXene (31.75%), due to the effect of photothermally assisted photocatalytic treatment. This work is an attempt to construct a visible light-driven antimicrobial material using Schottky junctions achieving photothermally assisted photocatalytic disinfection.

Hydroxylamine facilitated catalytic degradation of methylene blue in a Fenton-like system for heat-treatment modified drinking water treatment residues

Rational treatment of drinking water treatment residues (WTR) has become an environmental and social issue due to the risk of secondary contamination. WTR has been commonly used to prepare adsorbents because of its clay-like pore structure, but then requires further treatment. In this study, a Fenton-like system of H-WTR/HA/H₂O₂ was constructed to degrade organic pollutants in water. Specifically, WTR was modified by heat treatment to increase its adsorption active site, and to accelerate Fe(III)/Fe(II) cycling on the catalyst surface by the addition of hydroxylamine (HA). Moreover, the effects of pH, HA and H₂O₂ dosage on the degradation were discussed with methylene blue (MB) as the target pollutant. The mechanism of the action of HA was analyzed and the reactive oxygen species in the reaction system were determined. Combined with the reusability and stability experiments, the removal efficiency of MB remained 65.36% after 5 cycles. Consequently, this study may provide new insights into the resource utilization of WTR.

Interface engineering of sandwich SiO@α-FeO@COF core-shell S-scheme heterojunctions for efficient photocatalytic oxidation of gas-phase HS

Hydrogen sulfide (H₂S) is considered to be a broad-spectrum toxicant, and it is crucial to address this problem due to its serious health and climate change impacts. Photocatalysis can be effectively applied for the reduction of H₂S molecules to S and other products. We synthesized sandwich-structured composite materials with internally immobilized SiO₂ nanospheres and externally wrapped COF layers co-modified with iron oxide nanoparticles. Furthermore, originally looked at the efficiency of photocatalysis in reducing hydrogen sulfide to sulfur. In this paper, a sandwich structure of core-shell composite photocatalysts based on SiO₂ was prepared by a multi-step method including Stöber and double ligand-regulated solvent heat, and these sandwich core-shell structures exhibited high hydrogen sulfide reduction and stability in applications. In addition, characterization, degradation studies, active substance trapping studies, and energy band structure analysis showed that S-type heterojunctions could effectively increase photo-generated carrier separation. This research advanced knowledge of photocatalytic hydrogen sulfide reduction and offered a novel approach for catalysts in COF sandwich core-shell structures.

Two Birds with One Stone: Copper-Based Adsorbents Used for Photocatalytic Oxidation of Hg0 (Gas) after Removal of PH3

Cu_X/TiO₂ adsorbents with CuO as the active component were prepared via a simple impregnation method for efficient purification of phosphine (PH₃) under the conditions of low temperatures (90 °C) and low oxygen concentration (1%). The PH₃ breakthrough capacity of optimal adsorbent (Cu₃₀/TiO₂) is 136.2 mg(PH₃)·g_sorbent^-1, and the excellent dephosphorization performance is mainly attributed to its abundant sur face-active oxygen and alkaline sites, large specific surface area, and strong interaction between CuO and the support TiO₂. Surprisingly, CuO is converted to Cu₃P after the dephosphorization by Cu_X/TiO₂. Since Cu₃P is a P-type semiconductor with high added value, the deactivated adsorbent (Cu₃P/TiO₂) is an efficient heterostructure photocatalyst for photocatalytic removal of Hg⁰ (gas) with the Hg⁰ removal performance of 92.64% under visible light. This study provides a feasible strategy for the efficient removal and resource conversion of PH₃ under low-temperature conditions and the alleviation of the environmental risk of secondary pollution.

Recent Developments of Light-Harvesting Excitation, Macroscope Transfer and Multi-Stage Utilization of Photogenerated Electrons in Rotating Disk Photocatalytic Reactor

The rotating disk photocatalytic reactor is a kind of photocatalytic wastewater treatment technique with a high application potential, but the light energy utilization rate and photo quantum efficiency still need to be improved. Taking photogenerated electrons as the starting point, the following contents are reviewed in this work: (1) Light-harvesting excitation of photogenerated electrons. Based on the rotating disk thin solution film photocatalytic reactor, the photoanodes with light capture structures are reviewed from the macro perspective, and the research progress of light capture structure catalysts based on BiOCl is also reviewed from the micro perspective. (2) Macroscope transfer of photogenerated electrons. The research progress of photo fuel cell based on rotating disk reactors is reviewed. The system can effectively convert the chemical energy in organic pollutants into electrical energy through the macroscopic transfer of photogenerated electrons. (3) Multi-level utilization of photogenerated electrons. The photogenerated electrons transferred to the cathode can also generate H2O2 with oxygen or H2 with H+, and the reduction products can also be further utilized to deeply mineralize organic pollutants or reduce the nitrate in water. This short review will provide theoretical guidance for the further application of photocatalytic techniques in wastewater treatment.

Detecting and Quantifying Wavelength-Dependent Electrons Transfer in Heterostructure Catalyst via In Situ Irradiation XPS

The identity of charge transfer process at the heterogeneous interface plays an important role in improving the stability, activity, and selectivity of heterojunction catalysts. And, in situ irradiation X-ray photoelectron spectroscopy (XPS) coupled with UV light optical fiber measurement setup is developed to monitor and observe the photoelectron transfer process between heterojunction. However, the in-depth relationship of binding energy and irradiation light wavelength is missing based on the fact that the incident light is formed by coupling light with different wavelengths. Furthermore, a quantitative understanding of the charge transfer numbers and binding energy remains elusive. Herein, based on the g-C₃ N₄ /SnO₂ model catalyst, a wavelength-dependent Boltzmann function to describe the changes of binding energy and wavelength through utilizing a continuously adjustable monochromatic light irradiation XPS technique is established. Using this method, this study further reveals that the electrons transfer number can be readily calculated forming an asymptotic model. This methodology provides a blueprint for deep understanding of the charge-transfer rules in heterojunction and facilitates the future development of highly active advanced catalysts.

Boosting Reactive Oxygen Species Generation Using Inter-Facet Edge Rich WO3 Arrays for Photoelectrochemical Conversion

Water oxidation reaction leaves room to be improved in the development of various solar fuel productions, because of the kinetically sluggish 4-electron transfer process of oxygen evolution reaction. In this work, we realize reactive oxygen species (ROS), H₂ O₂ and OH⋅, formations by water oxidation with total Faraday efficiencies of more than 90 % by using inter-facet edge (IFE) rich WO₃ arrays in an electrolyte containing CO₃ ^2- . Our results demonstrate that the IFE favors the adsorption of CO₃ ^2- while reducing the adsorption energy of OH⋅, as well as suppresses surface hole accumulation by direct 1-electron and indirect 2-electron transfer pathways. Finally, we present selective oxidation of benzyl alcohol by in situ using the formed OH⋅, which delivers a benzaldehyde production rate of ≈768 μmol h^-1 with near 100 % selectivity. This work offers a promising approach to tune or control the oxidation reaction in an aqueous solar fuel system towards high efficiency and value-added product.

Synergistically interactive P-Co-N bonding states in cobalt phosphide-decorated covalent organic frameworks for enhanced photocatalytic hydrogen evolution

Non-noble materials with high efficiency and stability are essential for renewable energy applications. Herein, cobalt phosphide nanoparticles-decorated covalent organic frameworks (CTF-CoP) are synthesized via an in situ self-assembly method combined with the calcination process. In such a configuration, an intimate interaction between CoP and CTF matrix is gained through the Co-N chemical bonds, which not only significantly enhance the recyclability of CoP nanoparticles but also significantly improve the charge separation efficiency. Besides, the synergistically interactive P^δ--Co^δ+-N^δ- states induced by the polarization effect of N-anchoring sites benefit for the adsorption and dissociation of water molecules in CTF-CoP. Consequently, CTF-CoP exhibits a higher photocatalytic hydrogen evolution rate (261.7 μmol g^-1 h^-1) and better durability as compared with the physically fixed CTF/CoP composite (64.8 μmol g^-1 h^-1) and even the noble metal-based CTF-Pt (191.3 μmol g^-1 h^-1). This work provides an avenue to construct highly stable non-noble photocatalyst for energy conversion and also emphasizes the potential of CTFs in constructing efficient heterojunctions.

Activating C-H Bonds by Tuning Fe Sites and an Interfacial Effect for Enhanced Methanol Oxidation

The interaction mechanism between the reacting species and the active site of α-Fe₂ O₃ -based photoanodes in photoelectrochemical methanol conversion reaction is still ambiguous. Herein, a simple two-step strategy is demonstrated to fabricate a porous α-Fe₂ O₃ /CoFe₂ O₄ heterojunction for the methanol conversion reaction. The influence of the electronic structure of active site and interfacial effect on the reaction are investigated by constructing two different FeO₆ octahedral configurations and heterogeneous structures. The optimal sample ZnFeCo-2 affords high photocurrent density of 1.17 mA cm^-2 at 0.5 V vs Ag/AgCl, which is 3.2 times than that of ZnFe (0.37 mA cm^-2 ). Meanwhile, the ZnFeCo-2 also exhibits 97.8% Faraday efficiency of CH₃ OH to HCHO, and long-term stability over 40 h. Furthermore, density functional theory calculations reveal that the heterostructured α-Fe₂ O₃ /CoFe₂ O₄ with favorable electron transfer effectively lowers methanol adsorption, C-H bond activation, and HCHO desorption energy relative to the pristine α-Fe₂ O₃ , resulting in excellent methanol conversion efficiency.

A One-Stone-Two-Birds Strategy to Functionalized Carbon Nanocages

Carbon nanocages (CNCs) have attracted tremendous interest in heterogeneous catalysis due to their promising properties of porous structure and improved mass transfer. Nevertheless, the controlled synthesis of CNCs remains a great challenge. Herein, we have shown the successful construction of functionalized N-doped CNCs (NCNCs) via a one-stone-two-birds strategy. The selective use of hexacarbonyl molybdenum (Mo(CO)₆) can not only protect the profile of the ZIF-8 precursor from collapse during thermal treatment but also be sacrificed for the functionalization of NCNCs after pyrolysis. Detailed mechanism studies reveal that Mo(CO)₆ evolves into MoO₃ on the surface of ZIF-8 and then facilitates the rapid pyrolysis of ZIF-8, leading to the formation of NCNCs decorated with small-sized MoC nanoparticles (MoC/NCNCs). The versatility of this one-stone-two-birds strategy has been validated by the generations of Cr- and W-decorated NCNCs. Moreover, MoC/NCNCs can serve as a selective and stable catalyst for furfural hydrogenation. This work provides a facile and universal strategy for fabricating and functionalizing CNCs, which attracts research interest in the fields of chemistry, material science, catalysis, and beyond.

Development of γ-Al2O3 with oxygen vacancies induced by amorphous structures for photocatalytic reduction of CO2

Inducing amorphous components into Al₂O₃ leads to elongation of the Al-O bond and the formation of oxygen vacancies, which makes Al₂O₃ an independent photocatalyst for CO₂ adsorption and reduction. The generation rate of CO can reach 36.5 μmol g^-1 h^-1, which is 6.5 times that of P25 TiO₂.

Engineering Single-Atom Active Sites on Covalent Organic Frameworks for Boosting CO2 Photoreduction

Solar carbon dioxide (CO₂) conversion is an emerging solution to meet the challenges of sustainable energy systems and environmental/climate concerns. However, the construction of isolated active sites not only influences catalytic activity but also limits the understanding of the structure-catalyst relationship of CO₂ reduction. Herein, we develop a universal synthetic protocol to fabricate different single-atom metal sites (e.g., Fe, Co, Ni, Zn, Cu, Mn, and Ru) anchored on the triazine-based covalent organic framework (SAS/Tr-COF) backbone with the bridging structure of metal-nitrogen-chlorine for high-performance catalytic CO₂ reduction. Remarkably, the as-synthesized Fe SAS/Tr-COF as a representative catalyst achieved an impressive CO generation rate as high as 980.3 μmol g^-1 h^-1 and a selectivity of 96.4%, over approximately 26 times higher than that of the pristine Tr-COF under visible light irradiation. From X-ray absorption fine structure analysis and density functional theory calculations, the superior photocatalytic performance is attributed to the synergic effect of atomically dispersed metal sites and Tr-COF host, decreasing the reaction energy barriers for the formation of *COOH intermediates and promoting CO₂ adsorption and activation as well as CO desorption. This work not only affords rational design of state-of-the-art catalysts at the molecular level but also provides in-depth insights for efficient CO₂ conversion.

Preparation and Performance of a Cu@PtCu/CNF Oxygen Reduction Catalyst Membrane by Electrospinning

A flexible carbon nanofiber film with high conductivity was prepared by electrospinning, and then Cu was uniformly deposited on the fiber film by pulse electrodeposition to prepare Cu nanocrystal/carbon nanofiber film. Cu@PtCu/carbon nanofiber (Cu@PtCu/CNF) catalytic films were synthesized by in-situ substitution reduction. The Cu@PtCu/CNF catalytic film solves the problem of uneven activity of the catalytic layer and can be directly used as the catalytic layer. The morphology and structure were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Electrochemical test results show that the Cu@PtCu/CNF catalytic films obtained at the chloroplatinic acid concentration of 0.5 mg·mL^-1 (N2) exhibited 2.5 times specific activity when compared with commercial Pt/C catalysts. After 5000 cycles of stability test, the electrochemical surface areas (ECSAs) were still maintained at 80%, and the half-wave potential decreased by 11 mV, which was better than those of commercial Pt/C catalysts.

Regulation of coordination and doping environment via target molecular transformation for boosting selective photocatalytic ability

Here, a novel transformed CdO with low coordination and N doping environment was simply synthesized through the involvement of the target molecule tetracycline (TC). The results showed that the shedding of surface hydroxyl groups led to a low coordination environment, and N doping formed a new doping energy level, which increased the charge density and promoted the migration and separation of photo-generated carriers. Its photocatalytic performance was 4.32 times higher than that of hydroxy-rich CdO and the selectivity coefficient was 4.8. Combined with theoretical calculation and in situ Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) analysis, the significant improvement of selectivity was due to the interaction of the doped N atom with the methyl carbon in TC. This work provided a new idea for the simultaneous construction of low coordination environment and N-doped materials for efficient selective photocatalysis.

Boosting Interfacial Charge Transfer with a Giant Internal Electric Field in a TiO2 Hollow-Sphere-Based S-Scheme Heterojunction for Efficient CO2 Photoreduction

The construction of an S-scheme charge transfer pathway is considered to be a powerful way to inhibit charge recombination and maintain photogenerated carriers with high redox capacity to meet the kinetic requirements of the carbon dioxide (CO₂) photoreduction reaction. For an S-scheme heterojunction, an internal electric field (IEF) is regarded as the main driving force for accelerating the interfacial spatial transfer of photogenerated charges. Herein, we designed a TiO₂ hollow-sphere (TH)-based S-scheme heterojunction for efficient CO₂ photoreduction, in which WO₃ nanoparticles (WP) were applied as an oxidation semiconductor to form an intimate interfacial contact with the TH. The S-scheme charge transfer mode driven by a strong IEF for the TH/WP composite was confirmed by in situ X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. As a result, abundant photogenerated electrons with strong reducing ability would take part in the CO₂ reduction reaction. The combination of surface photovoltage spectra and transient photocurrent experiments disclosed that the IEF intensity and charge separation efficiency of the fabricated TH/WP composite were nearly 16.80- and 1.42-fold higher, respectively, than those of the pure TH. Furthermore, sufficient active sites provided by the hollow-sphere structure also enhanced the kinetics of the catalytic reaction. Consequently, the optimized TH/WP composite showed a peak level of CO production of 14.20 μmol g^-1 in 3 h without the addition of any sacrificial agent. This work provides insights into the kinetic studies of the S-scheme charge transfer pathway for realizing high-performance CO₂ photoreduction.

1D α-Fe2O3/ZnO Junction Arrays Modified by Bi as Photocathode: High Efficiency in Photoelectrochemical Reduction of CO2 to HCOOH

Photoelectrocatalytic (PEC) CO₂ reduction to value-added chemicals is a promising solution to address the energy and environmental issues we face currently. Herein, a unique photocathode Bi@ZFO NTs (Bi and α-Fe₂O₃ co-modified ZnO nanorod arrays) with high utilization of visible light and sharp-tips effect are successfully prepared using a facile method. Impressively, the performance of Bi@ZFO NTs for PEC CO₂ reduction to HCOOH included small onset potential (-0.53 V vs RHE), Tafel slope (101.2 mV dec^-1), and a high faraday efficiency of 61.2% at -0.65 V vs RHE as well as favorable stability over 4 h in an aqueous system under visible light illumination. Also, a series of experiments were performed to investigate the origin of its high activity, indicating that the metallic Bi and α-Fe₂O₃/ZnO nanojunction should be responsible for the favorable CO₂ adsorption/activation and charge transition/carrier separation, respectively. Density functional theory calculations reveal that the Bi@ZFO NTs could lower the intermediates' energy barrier of HCOO* and HCOOH* to form HCOOH due to the strong interaction of Bi and α-Fe₂O₃/ZnO.

Carbon nitride-based Z-scheme heterojunctions for solar-driven advanced oxidation processes

Solar-driven advanced oxidation processes (AOPs) via direct photodegradation or indirect photocatalytic activation of typical oxidants, such as hydrogen peroxide (H₂O₂), peroxymonosulfate (PMS), and peroxydisulfate (PDS), have been deemed to be an efficient technology for wastewater remediation. Artificial Z-scheme structured materials represent a promising class of photocatalysts due to their spatially separated charge carriers and strong redox abilities. Herein, we summarize the development of metal-free graphitic carbon nitride (g-C₃N₄, CN)-based direct and indirect Z-scheme photocatalysts for solar-driven AOPs in removing organic pollutants from water. In the work, the classification of AOPs, definition and validation of Z-schemes are summarized firstly. The innovative engineering strategies (e.g., morphology and dimensionality control, element doping, defect engineering, cocatalyst loading, and tandem Z-scheme construction) over CN-based direct Z-scheme structure are then examined. Rational design of indirect CN-based Z-scheme systems using different charge mediators, such as solid conductive materials and soluble ion pairs, is further discussed. Through examining the relationship between the Z-scheme structure and activity (charge transfer and separation, light absorption, and reaction kinetics), we aim to provide more insights into the construction strategies and structure modification on CN-based Z-schemes towards improving their catalytic performances in AOPs. Lastly, limitations, challenges, and perspectives on future development in this emerging field are proposed.

Synergy in Au-CuO Janus Structure for Catalytic Isopropanol Oxidative Dehydrogenation to Acetone

The controlled oxidation of alcohols to the corresponding ketones or aldehydes via selective cleavage of the β-C-H bond of alcohols under mild conditions still remains a significant challenge. Although the metal/oxide interface is highly active and selective, the interfacial sites fall far behind the demand, due to the large and thick support. Herein, we successfully develop a unique Au-CuO Janus structure (average particle size=3.8 nm) with an ultrathin CuO layer (0.5 nm thickness) via a bimetal in situ activation and separation strategy. The resulting Au-CuO interfacial sites prominently enhance isopropanol adsorption and decrease the energy barrier of β-C-H bond scission from 1.44 to 0.01 eV due to the strong affinity between the O atom of CuO and the H atom of isopropanol, compared with Au sites alone, thereby achieving ultrahigh acetone selectivity (99.3 %) over 1.1 wt % AuCu_0.75 /Al₂ O₃ at 100 °C and atmospheric pressure with 97.5 % isopropanol conversion. Furthermore, Au-CuO Janus structures supported on SiO₂ , TiO₂ or CeO₂ exhibit remarkable catalytic performance, and great promotion in activity and acetone selectivity is achieved as well for other reducible oxides derived from Fe, Co, Ni and Mn. This study should help to develop strategies for maximized interfacial site construction and structure optimization for efficient β-C-H bond activation.

Directing Charge Transfer in a Chemical-Bonded BaTiO3 @ReS2 Schottky Heterojunction for Piezoelectric Enhanced Photocatalysis

The piezo-assisted photocatalysis system, which can utilize solar energy and mechanical energy simulteneously, is promising but still challenging in the environmental remediation field. In this work, a novel metal-semiconductor BaTiO₃ @ReS₂ Schottky heterostructure is designed and it shows high-efficiency on piezo-assisted photocatalytic molecular oxygen activation. By combining experiment and calculation results, the distorted metal-phase ReS₂ nanosheets are found to be closely anchored on the surface of the BaTiO₃ nanorods, through interfacial ReO covalent bonds. The Schottky heterostructure not only forms electron-transfer channels but also exhibits enhanced oxygen activation capacity, which are helpful to produce more superoxide radicals. The polarization field induced by the piezoelectric BaTiO₃ can lower the Schottky barrier and thus reduce the transfer resistance of photogenerated electrons directing to the ReS₂ . As a result of the synergy effect between the two components, the BaTiO₃ @ReS₂ exhibits untrahigh activity for degradation of pollutants with an apparent rate constant of 0.133 min^-1 for piezo-assisted photocatalysis, which is 16.6 and 2.44 times as that of piezocatalysis and photocatalysis, respectively. This performance is higher than most reported BaTiO₃ -based piezo-assisted photocatalysis systems. This work paves the way for the design of high-efficiency piezo-assisted photocatalytic materials for environmental remediation through using green energies in nature.

Efficient Interfacial Charge Transfer Based on 2D/2D Heterojunctions of Fe-C3N4/Ti3C2 for Improving the Photocatalytic Degradation of Antibiotics

Graphitic carbon nitride (g-C₃N₄) has shown to be a promising photocatalyst that, however, suffers from strong charge recombination and poor conductivity, while MXenes have shown to be perfect cocatalysts for the photocatalytic process but show poor stability. In this study, we successfully constructed 2D/2D heterojunctions of Fe-C₃N₄/Ti₃C₂ for the photocatalytic degradation of antibiotics. In this study, multilayer Ti₃C₂ was obtained by etching Ti₃AlC₂, and then Fe-C₃N₄/Ti₃C₂ photocatalyst was prepared by the one-pot microwave method and high-temperature calcination method. The synthesized samples were characterized by XRD, SEM, TEM, XPS, TGA, BET, DRS, PL, and other means. The photocatalytic degradation of tetracycline hydrochloride by Fe-C₃N₄/Ti₃C₂ was in accordance with the first-order reaction kinetics model, and the apparent rate constant k was 2.83, 2.06, and 1.77 times that of g-C₃N₄, Fe-C₃N₄, and g-C₃N₄/Ti₃C₂, respectively. Through the mechanism study, it was shown that the most active species in the reaction system was • O₂⁻, while h⁺ and •OH had a relatively lower effect on the degradation system.

Engineering MoOx /MXene Hole Transfer Layers for Unexpected Boosting of Photoelectrochemical Water Oxidation

The development of semiconductor photoanodes is of great practical interest for the realization of photoelectrochemical (PEC) water splitting. Herein, MXene quantum dots (MQD) were grafted on a BiVO₄ substrate, then a MoO_x layer by combining an ultrathin oxyhydroxide oxygen evolution cocatalyst (OEC) was constructed as an integrated photoanode. The OEC/MoO_x /MQD/BiVO₄ array not only achieves a current density of 5.85 mA cm^-2 at 1.23 V versus a reversible hydrogen electrode (vs. RHE), but also enhances photostability. From electrochemical analysis and density functional theory calculations, high PEC performance is ascribed to the incorporation of MoO_x /MQD as hole transfer layers, retarding charge recombination, promoting hole transfer and accelerating water splitting kinetics. This proof-of-principle work not only demonstrates the potential utilization of hole transfer layers, but also sheds light on rational design and fabrication of integrated photoanodes for feasible solar energy conversion.