Defect engineering in metal sulfides for energy conversion and storage

Glutathione-mediated copper sulfide nanoplatforms with morphological and vacancy-dependent photothermal catalytic activity for multi-model tannic acid assays

Interface engineering and vacancy engineering play an important role in the surface and electronic structure of nanomaterials. The combination of the two provides a feasible way for the development of efficient photocatalytic materials. Here, we use glutathione (GSH) as a coordination molecule to design a series of CuxS nanomaterials (CuxS-GSH) rich in sulfur vacancies using a simple ultrasonic-assisted method. Interface engineering can induce amorphous structure in the crystal while controlling the formation of porous surfaces of nanomaterials, and the formation of a large number of random orientation bonds further increases the concentration of sulfur vacancies in the crystal structure. This study shows that interface engineering and vacancy engineering can enhance the light absorption ability of CuxS-GSH nanomaterials from the visible to the near-infrared region, improve the efficiency of charge transfer between CuxS groups, and promote the separation and transfer of optoelectronic electron-hole pairs. In addition, a higher specific surface area can produce a large number of active sites, and the synergistic and efficient photothermal conversion efficiency (58.01%) can jointly promote the better photocatalytic performance of CuxS-GSH nanomaterials. Based on the excellent hot carrier generation and photothermal conversion performance of CuxS-GSH under illumination, it exhibits an excellent ability to mediate the production of reactive oxygen species (ROS) through peroxide cleavage and has excellent peroxidase activity. Therefore, CuxS-GSH has been successfully developed as a nanoenzyme platform for detecting tannic acid (TA) content in tea, and convenient and rapid detection of tannic acid is achieved through the construction of a multi-model strategy. This work not only provides a new way to enhance the enzyme-like activity of nanomaterials but also provides a new prospect for the application of interface engineering and vacancy engineering in the field of photochemistry.

A review on defect modulated electrocatalysts for the oxygen evolution reaction

The oxygen evolution reaction (OER) is crucial for applications such as water splitting and rechargeable metal-air batteries. Recent research has focused on improving the activity and stability of OER electrocatalysts through various strategies including structural innovation, heteroatom doping, and conductivity enhancement. Among these, defect engineering has proved particularly effective, allowing precise modulation of the materials' electronic structure at the atomic level. This review addresses defect-rich materials that exhibit superior electrochemical properties for OER applications, with a particular focus on developments from the past five years. The discussion starts with an overview of the OER catalytic mechanism and then delves into the types of defects, synthesis methods, and their impact on electrochemical performance. This review concludes with insights into the rational design and synthesis of advanced electrocatalysts, aiming to improve efficiency and extend operational longevity. The objective is to highlight approaches for creating high-performance OER electrocatalysts that outperform noble-metal based systems in both activity and stability.

Trifunctional L-Cysteine Assisted Construction of MoO2/MoS2/C Nanoarchitecture Toward High-Rate Sodium Storage

The volume collapse and slow kinetics reaction of anode materials are two key issues for sodium ion batteries (SIBs). Herein, an "embryo" strategy is proposed for synthesis of nanorod-embedded MoO2/MoS2/C network nanoarchitecture as anode for SIBs with high-rate performance. Interestingly, L-cysteine which plays triple roles including sulfur source, reductant, and carbon source can be utilized to produce the sulfur vacancy-enriched heterostructure. Specifically, L-cysteine can combine with metastable monoclinic MoO3 nanorods at room temperature to encapsulate the "nutrient" of MoOx analogues (MoO2.5(OH)0.5 and MoO3·0.5H2O) and hydrogen-deficient L-cysteine in the "embryo" precursor affording for subsequent in situ multistep heating treatment. The resultant MoO2/MoS2/C presents a high-rate capability of 875 and 420 mAh g-1 at 0.5 and 10 A g-1, respectively, which are much better than the MoS2-based anode materials reported by far. Finite element simulation and analysis results verify that the volume expansion can be reduced to 42.8% from 88.8% when building nanorod-embedded porous network structure. Theoretical calculations reveal that the sulfur vacancies and heterointerface engineering can promote the adsorption and migration of Na+ leading to highly enhanced thermodynamic and kinetic reaction. The work provides an efficient approach to develop advanced electrode materials for energy storage.

A Review of the Effect of Defect Modulation on the Photocatalytic Reduction Performance of Carbon Dioxide

Constructive defect engineering has emerged as a prominent method for enhancing the performance of photocatalysts. The mechanisms of the influence of defect types, concentrations, and distributions on the efficiency, selectivity, and stability of CO2 reduction were revealed for this paper by analyzing the effects of different types of defects (e.g., metallic defects, non-metallic defects, and composite defects) on the performance of photocatalysts. There are three fundamental steps in defect engineering techniques to promote photocatalysis, namely, light absorption, charge transfer and separation, and surface-catalyzed reactions. Defect engineering has demonstrated significant potential in recent studies, particularly in enhancing the light-harvesting, charge separation, and adsorption properties of semiconductor photocatalysts for reducing processes like carbon dioxide reduction. Furthermore, this paper discusses the optimization method used in defect modulation strategy to offer theoretical guidance and an experimental foundation for designing and preparing efficient and stable photocatalysts.

Biomass-Derived Carbon Materials for Electrochemical Energy Storage

The environmental impact from the waste disposal has been widely concerned around the world. The conversion of wastes to useful resources is important for the sustainable society. As a typical family of wastes, biomass materials basically composed of collagen, protein and lignin are considered as useful resources for recycle and reuse. In recent years, the development of carbon material derived from biomasses, such as plants, crops, animals and their application in electrochemical energy storage have attracted extensive attention. Through the selection of the appropriate biomass, the optimization of the activation method and the control of the pyrolysis temperatures, carbon materials with desired features, such as high-specific surface area, variable porous framework, and controllable heteroatom-doping have been fabricated. Herein, this review summarized the preparation methods, morphologies, heteroatoms doping in the plant/animal-derived carbonaceous materials, and their application as electrode materials for secondary batteries and supercapacitors, and as electrode support for lithium-sulfur batteries. The challenges and prospects for the controllable synthesis and large-scale application of biomass-derived carbonaceous materials have also been outlooked.

Distinctive p-d Orbital Hybridization in CuSb Porous Nanonetworks for Enhanced Nitrite Electroreduction to Ammonia

Electrochemical nitrite reduction reaction (NO 2 - RR ${\mathrm{NO}}_{\mathrm{2}}^{\mathrm{ - }}{\mathrm{RR}}$ ), as a green and sustainable ammonia synthesis technology, has broad application prospects and environmental friendliness. Herein, an unconventional p-d orbital hybridization strategy is reported to realize the fabrication of defect-rich CuSb porous nanonetwork (CuSb PNs) electrocatalyst forNO 2 - RR ${\mathrm{NO}}_{\mathrm{2}}^ - {\mathrm{RR}}$ . The crystalline/amorphous heterophase structure is cleverly introduced into the porous nanonetworks, and this defect-rich structure exposes more atoms and activated boundaries. CuSb PNs exhibit a large NH3 yield (r N H 3 ${{r}_{{\mathrm{N}}{{{\mathrm{H}}}_{\mathrm{3}}}}}$ ) of 946.1 µg h-1m cat - 1 ${\mathrm{m}}_{{\mathrm{cat}}}^{ - {\mathrm{1}}}$ and a high faradaic efficiency (FE) of 90.7%. Experimental and theoretical studies indicate that the excellent performance of CuSb PNs results from the defect-rich porous nanonetworks structure and the p-d hybridization of Cu and Sb elements. This work describes a powerful pathway for the fabrication of p-d orbital hybrid defect-rich porous nanonetworks catalysts, and provides hope for solving the problem of nitrogen oxide pollution in the field of environment and energy.

A Defective Disc-Like Cu1.96 S Anode Material with the Efficient Cu Vacancies for High-Performance Sodium-Ion Storage

Due to their significant capacity and reliable reversibility, transition metal sulphides (TMSs) have received attention as potential anode materials for sodium-ion batteries (SIBs). Nonetheless, a prevalent challenge with TMSs lies in their significant volume expansion and sluggish kinetics, impeding their capacity for rapid and enduring Na+ storage. Herein, a Cu1.96 S@NC nanodisc material enriched with copper vacancies is synthesised via a hydrothermal and annealing procedure. Density functional theory (DFT) calculations reveal that the incorporation of copper vacancies significantly boosts electrical conductivity by reducing the energy barrier for ion diffusion, thereby promoting efficient electron/ion transport. Moreover, the presence of copper vacancies creates ample active sites for the integration of sodium ions, streamlines charge transfer, boosts electronic conductivity, and, ultimately, significantly enhances the overall performance of SIBs. This novel anode material, Cu1.96 S@NC, demonstrates a reversible capacity of 339 mAh g-1 after 2000 cycles at a rate of 5 A g-1 . In addition, it maintains a noteworthy reversible capacity of 314 mAh g-1 with an exceptional capacity retention of 96% even after 2000 cycles at 20 A g-1 . The results demonstrate that creating cationic vacancies is a highly effective strategy for engineering anode materials with high capacity and rapid reactivity.

Design and fabrication of MoO42--intercalated LDH nanosheets coated on Co9S8 nanotubes with enhanced cycling stability for high-performance supercapacitors

Transition metal sulfides are promising electrode materials for supercapacitors due to their excellent electrochemical performance and high conductivity. Unfortunately, the low rate performance and poor cycling stability limited their progress towards commercial applications. Herein, the core-shell structure of MoO42--intercalated LDHs coated on Co9S8 nanotubes was rationally designed and prepared to improve their electrochemical performance and cycling stability by adjusting the composition of LDHs. Compared to NiMo-LDH@Co9S8 and CoMo-LDH@Co9S8, the optimized NiCoMo-LDH@Co9S8 electrode exhibits excellent areal specific capacitance (11 F cm-2 at 3 mA cm-2) and excellent cycling stability (94.4% after 5000 cycles). In addition, asymmetric supercapacitor devices were assembled with NiCoMo-LDH@Co9S8 and activated carbon (AC), which delivered a high energy density of 0.94 mWh cm-2, at a power density of 1.70 mW cm-2, and good cycling stability (89.4% after 5000 cycles). These results indicate that the introduction of MoO42- can enhance the synergistic effect of multiple metals and the synthesized NiCoMo-LDH@Co9S8 core-shell composite has great potential in the development of high-performance electrode materials for supercapacitors.

Dual-defect semiconductor photocatalysts for solar-to-chemical conversion: advances and challenges

Among the renewable energy technologies to deal with increasing energy crisis and environmental concerns, solar-to-chemical conversion via photocatalysis holds great promise for sustainable energy supply. To date, a variety of modification strategies with different types of semiconducting materials have been proposed to boost photocatalytic efficiency. Recently, dual-defect semiconductor photocatalysts have emerged as an advantageous candidate with superior performance in improving photocatalytic activity compared to their defect-free or single-defect counterparts. In this review, focus is laid on the advances of dual-defect semiconductor photocatalysts for energy photocatalysis. Possible schemes for two different defects within a single semiconductor are firstly sorted based on the types of defects, and synthesis strategies to achieve various defect schemes as well as techniques to characterize different defects are then introduced. In particular, the effect of different defects on photocatalytic performance is emphasized, and the advances in dual-defect semiconductors for solar-to-chemical conversions are summarized based on different defect schemes. Finally, the future challenges and opportunities of dual-defect semiconductors for photocatalysis are discussed. This article is expected to provide an overall insight into existing dual-defect semiconductor photocatalysts and inspire the development of new defect-rich materials for photocatalytic energy production.

Copious Dislocations Defect in Amorphous/Crystalline/Amorphous Sandwiched Structure P-NiMoO4 Electrocatalyst toward Enhanced Hydrogen Evolution Reaction

The design and synthesis of efficient, inexpensive, and long-term stable heterostructured electrocatalysts with high-density dislocations for hydrogen evolution reaction in alkaline media and seawater are still a great challenge. An amorphous/crystalline/amorphous sandwiched structure with abundant dislocations were synthesized through thermal phosphidation strategies. The dislocations play an important role in the hydrogen evolution reactions. Copious dislocation defects, combined with cracks, and the synergistic interfacial effect between crystalline phase and amorphous phase regulate the electronic structure of electrocatalyst, provide more active sites, and thus endow the electrocatalysts with excellent catalytic activity under alkaline water and seawater. The overpotentials of P-NiMoO4 at 10 mA/cm2 in 1 M KOH aqueous solution and seawater are 45 and 75 mV, respectively. Additionally, the P-NiMoO4 electrocatalyst exhibits long-term stability over 100 h. This study provides a simple approach for synthesizing amorphous/crystalline/amorphous sandwiched non-noble-metal electrocatalysts with abundant dislocations for hydrogen evolution reaction.

Oxygen vacancy modulated Fe-doped Co3O4 hollow nanosheet arrays for efficient oxygen evolution reaction

Herein, Fe-doped Co3O4 hollow nanosheet arrays with rich oxygen vacancies (Vo-Fe-Co3O4) are constructed using a facile strategy. Benefiting from the compositional and structural superiorities, Vo-Fe-Co3O4 exhibits a remarkable OER overpotential of 231 mV at 10 mA cm-2 and a Tafel slope of 57.45 mV dec-1 in an alkaline medium.

Ultrathin MnO2 with strong lattice disorder for catalytic oxidation of volatile organic compounds

Catalytic oxidation proves the most promising technology for volatile organic compounds (VOCs) abatement. Lattice disorder plays a crucial role in the catalytic activity of catalysts due to the exposure of more active sites. Inspired by this, we successfully prepared a series of ε-MnO2 with different lattice disorder defects via several simple methods and applied them to the catalytic oxidation of two typical VOCs (toluene and acetone). Various characterizations and performance tests confirm that the ultrathin (1.4-1.8 nm) structure and strong lattice disorder can enhance the low temperature reduction and reactive oxygen species, so that MnO2-R exhibits excellent toluene and acetone oxidation activities. In-situ DRIFTS tests were carried out to detect reaction intermediates in the toluene and acetone oxidation process on the catalyst surface. Moreover, we propose a possible synergistic mechanism for toluene and acetone mixtures catalytic oxidation. This work reveals the important role of lattice disorder defects in the catalytic oxidation of VOCs on Mn-based catalysts, and deepens the insights of the reaction path in toluene and acetone catalytic oxidation.

A comprehensive review on the boosted effects of anion vacancy in the heterogeneous photocatalytic degradation, part I: Focus on sulfur, nitrogen, carbon, and halogen vacancies

The greenest environmental remediation way is the photocatalytic degradation of organic pollutants. However, limited photocatalytic applications are due to poor sunlight absorption and photogenerated charge carriers' recombination. These limitations can be overcome by introducing anion vacancy (AV) (O, S, N, C, and Halogen) defects in semiconductors that enhance light harvesting, facilitate charge separation, modulate electronic structure, and produce reactive radicals. In continuing part A of this review, in this part, we summarized the recent AVs' research, including S, N, C, and halogen vacancies on the boosted photocatalytic features of semiconductor materials, like metal oxides/sulfides, oxyhalides, and nitrides in detail. Also, we outline the recently developed AV designs for the photocatalytic degradation of organic pollutants. The AV creating and analysis methods and the recent photocatalytic applications and mechanisms of AV-mediated photocatalysts are reviewed. AV engineering photocatalysts' challenges and development prospects are illustrated to get a promising research direction.

Self-Constructing 100% Water-Resistant Metal Sulfides through In Situ Acid Etching for Effective Elemental Mercury (Hg0) Capture

Metal sulfides (MSs) can efficiently entrap thiophilic components, such as elemental mercury (Hg0), and realize environmental remediation. However, there is still a critical problem challenging the extensive application of MSs in related areas, i.e., how to self-regulate their water (H2O) resistance without complexing the sorbent preparation procedure. This work for the first time developed an in situ acid-etching method that self-engineered the water affinity of MSs through changing the interfacial interaction between MSs and Hg0/H2O. The introduction of abundant, undercoordinated sulfur onto the sorbent surface was the primary reason accounting for the significantly improved H2O resistance. The high surface coverage of undercoordinated sulfur induced the formation of polysulfur chains (Sx2-) that stabilized Hg0 via a bridging bond and repelled H2O, attributed to the favorable electron configurations. These properties made the surface of MSs highly hydrophobic and increased the adsorption selectivity toward Hg0 over H2O. The MSs exhibited 100% H2O resistance even in the presence of 20% H2O, which is much higher than the H2O concentration under most practical scenarios. From these perspectives, this work for the first time overcame the detrimental effects of H2O on MSs through a self-regulating way that is scalable and negligibly complexes the sorbent preparation pathway. The highly water-resistant and cost-effective MSs as prepared can serve as efficient Hg0 removal from industrial flue gas in the future.

A Highly NIR Emissive Cu16 Pd1 Nanocluster

The construction of stable copper nanoclusters (Cu-NCs) with near-infrared (NIR) emission that can be used for catalysis is highly desired, yet remains a challenge. Herein, an atomically precise bimetallic Cu/Pd NC with a molecular formula of Cu16 Pd1 L10 (PPh3 )2 (Pz)6 (Pz = 3,5-(CF3 )2 Pyrazolate, L = 4-CH3 OPhC≡C- ), abbreviated as Cu16 Pd1 , is synthesized. Single-crystal X-ray crystallographic analysis of Cu16 Pd1 reveals a Cu10 Pd1 kernel with pseudo-gyroelongated square bipyramid confirmation surrounded by other 6 Cu(I) ions and protected ligands. Interestingly, it exhibits strong NIR emission with the highest photoluminescence quantum yield (PLQY) among all the Cu NCs/Cu alloys (λem  > 800 nm) in the solid-state, and also displays NIR emission in solution. Experimental results and theoretical calculations suggest that the impressive NIR emission is attributed to abundant supramolecular interactions in the solid-state, including intramolecular metal-metal and intermolecular interactions. Of note, the bimetallic Cu16 Pd1 can catalyze the reduction of 4-nitrophenol. This work provides a novel method for synthesizing Cu/Pd NCs and reminds that the less studied Cu/Pd NC can serve as outstanding luminescent material, which is seldom noticed in atomically precise nanoclusters.

Designing Surface-Defect Engineering to Enhance the Solar-Driven Conversion of CO2 to C2 Products over Zn3In2S6/ZnS

The manipulation of electronic structure and prevention of photogenerated carriers from being quenched in bulk defects during the photocatalytic CO2 reduction reaction (CRR) have been effectively demonstrated through surface vacancy and defect engineering. In this work, the electronic structure on the surface of Zn3In2S6/ZnS (ZIS/ZnS) is significantly modified by the introduction and control of the surface S vacancies (SV) through Ar-plasma treatment. EPR and XPS analyses confirmed that SV was exclusively present on the ZIS/ZnS surface. The resulting ZIS/ZnS heterojunction photocatalysts demonstrate an impressive 46.6% selectivity toward C2 products even in the absence of cocatalysts. The mechanism of photocatalytic CRR is further elucidated through in situ analysis. Theoretical calculations demonstrate that the presence of In and Zn atoms adjacent to SV significantly enhances the adsorption of CO2 and facilitates C-C coupling.

Imperfect makes perfect: defect engineering of photoelectrodes towards efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting for hydrogen evolution has been considered as a promising technology to solve the energy and environmental issues. However, the solar-to-hydrogen (STH) conversion efficiencies of current PEC systems are far from meeting the commercial demand (10%) due to the lack of efficient photoelectrode materials. The recent rapid development of defect engineering of photoelectrodes has significantly improved the PEC performance, which is expected to break through the bottleneck of low STH efficiency. In this review, the category and the construction methods of different defects in photoelectrode materials are summarized. Based on the in-depth summary and analysis of existing reports, the PEC performance enhancement mechanism of defect engineering is critically discussed in terms of light absorption, carrier separation and transport, and surface redox reactions. Finally, the application prospects and challenges of defect engineering for PEC water splitting are presented, and the future research directions in this field are also proposed.

Sulfur Substitution and Defect Engineering in an Unfavored MnMoO4 Catalyst for Efficient Hydrogen Evolution under Visible Light

A novel and nonstoichiometric Mn_1-xMo(S,O)_4-y oxysulfide catalyst with oxygen vacancies and a partial Mo⁶⁺-to-Mo⁴⁺ transition after the substitution of sulfur was synthesized for an efficient photocatalytic hydrogen evolution reaction (PHER). With appropriate sulfur substitution, a MnMoO₄ semiconductor with a wide band gap was converted to Mn_1-xMo(S,O)_4-y with a narrow gap and a suitable band position for PHER. MnMo oxysulfide of 50 mg achieved a high PHER rate of 415.8 μmol/h under visible light, an apparent quantum efficiency (AQE) of 4.31% at 420 nm, and a solar-to-hydrogen (STH) conversion efficiency of 1.28%. Oxygen vacancies (V_O) surrounded by low coordination metal atoms act as active reaction sites, which strengthen water adsorption and activation. Here, we demonstrate that sulfur substitution of MnMoO₄ for lowering its wide band gap can not only disturb the strict periodicity of the lattice but also the valence states of Mn and Mo for enhancing PHER via material design.

Dynamic phase evolution of MoS3 accompanied by organodiselenide mediation enables enhanced performance rechargeable lithium battery

Considerable efforts have been devoted to Li-S batteries, typically the soluble polysulfides shuttling effect. As a typical transition metal sulfide, MoS2 is a magic bullet for addressing the issues of Li-S batteries, drawing increasing attention. In this study, we introduce amorphous MoS3 as analogous sulfur cathode material and elucidate the dynamic phase evolution in the electrochemical reaction. The metallic 1T phase incorporated 2H phase MoS2 with sulfur vacancies (SVs-1T/2H-MoS2) decomposed from amorphous MoS3 achieves refined mixing with the "newborn" sulfur at the molecular level and supplies continuous conduction pathways and controllable physical confinement. Meanwhile, the in situ-generated SVs-1T/2H-MoS2 allows lithium intercalation in advance at high discharge voltage (≥1.8 V) and enables fast electron transfer. Moreover, aiming at the unbonded sulfur, diphenyl diselenide (PDSe), as a model redox mediator is applied, which can covalently bond sulfur atoms to form conversion-type organoselenosulfides, changing the original redox pathway of "newborn" sulfur in MoS3, and suppressing the polysulfides shuttling effect. It also significantly lowers the activation energy and thus accelerates the sulfur reduction kinetics. Thus, the in situ-formed intercalation-conversion hybrid electrode of SVs-1T/2H-MoS2 and organoselenosulfides realizes enhanced rate capability and superior cycling stability. This work provides a novel concept for designing high-energy-density electrode materials.

Vein-Like Ni-BTC@Ni3S4 with Sulfur Vacancy and Ni3+ Fabricated In Situ Etching Vulcanization Strategy for an Electrochemical Sensor of Dopamine

In this study, a novel Ni-BTC@Ni₃S₄ composite was fabricated by solvothermal reaction using an in situ etching vulcanization strategy and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and Brunauer-Emmett-Teller (BET) analyses. The existence of a sulfur vacancy and Ni³⁺ in the as-prepared vein-like Ni-BTC@Ni₃S₄ greatly promoted the electrochemical sensing activity of the materials. Herein, a simple electrochemical sensor (Ni-BTC@Ni₃S₄/CPE) has been fabricated and used for the detection of dopamine (DA). The current signal of the Ni-BTC@Ni₃S₄/CPE-modified electrode was linear with the concentration of DA in the range of 0.05-750 μM (R² = 0.9995) with a sensitivity of 560.27 μA·mM^-1·cm^-2 and a detection limit of 0.016 μM. At the same time, the sensor has good stability and anti-interference ability. This study could provide a new idea and strategy for the structural regulation of composite electrode-modified materials and sensitive sensing detection of small biological molecules.

Defect engineering of two-dimensional materials for advanced energy conversion and storage

In the global trend towards carbon neutrality, sustainable energy conversion and storage technologies are of vital significance to tackle the energy crisis and climate change. However, traditional electrode materials gradually reach their property limits. Two-dimensional (2D) materials featuring large aspect ratios and tunable surface properties exhibit tremendous potential for improving the performance of energy conversion and storage devices. To rationally control the physical and chemical properties for specific applications, defect engineering of 2D materials has been investigated extensively, and is becoming a versatile strategy to promote the electrode reaction kinetics. Simultaneously, exploring the in-depth mechanisms underlying defect action in electrode reactions is crucial to provide profound insight into structure tailoring and property optimization. In this review, we highlight the cutting-edge advances in defect engineering in 2D materials as well as their considerable effects in energy-related applications. Moreover, the confronting challenges and promising directions are discussed for the development of advanced energy conversion and storage systems.

Switching of radical and nonradical pathways through the surface defects of Fe3O4/MoOxSy in a Fenton-like reaction

Coexistence of radical and nonradical reaction pathways during advanced oxidation processes (AOPs) makes it challenging to obtain flexible regulation of high efficiency and selectivity for the requirement of diverse degradation. Herein, a series of Fe₃O₄/MoO_xS_y samples coupling peroxymonosulfate (PMS) systems enabled the switching of radical and nonradical pathways through the inclusion of defects and adjustment of Mo⁴⁺/Mo⁶⁺ ratios. The silicon cladding operation introduced defects by disrupting the original lattice of Fe₃O₄ and MoO_xS. Meanwhile, the abundance of defective electrons increased the amount of Mo⁴⁺ on the catalyst surface, promoting PMS decomposition with a maximum k value up to 1.530 min^-1 and a maximum free radical contribution of 81.33%. The Mo⁴⁺/Mo⁶⁺ ratio in the catalyst was similarly altered by different Fe contents, and Mo⁶⁺ contributed to the production of ¹O₂, allowing the whole system to attain a nonradical species-dominated (68.26%) pathway. The radical species-dominated system has a high chemical oxygen demand (COD) removal rate for actual wastewater treatment. Conversely, the nonradical species-dominated system can considerably improve the biodegradability of wastewater (biochemical oxygen demand (BOD)/COD = 0.997). The tunable hybrid reaction pathways will expand the targeted applications of AOPs.

Ultrafast Combustion Synthesis of Robust and Efficient Electrocatalysts for High-Current-Density Water Oxidation

The scalable production of inexpensive, efficient, and robust catalysts for oxygen evolution reaction (OER) that can deliver high current densities at low potentials is critical for the industrial implementation of water splitting technology. Herein, a series of metal oxides coupled with Fe2O3 are in situ grown on iron foam massively via an ultrafast combustion approach for a few seconds. Benefiting from the three-dimensional nanosheet array framework and the heterojunction structure, the self-supporting electrodes with abundant active centers can regulate mass transport and electronic structure for prompting OER activity at high current density. The optimized Ni(OH)2/Fe2O3 with robust structure can deliver a high current density of 1000 mA cm-2 at the overpotential as low as 271 mV in 1.0 M KOH for up to 1500 h. Theoretical calculation demonstrates that the strong electronic modulation plays a crucial part in the hybrid by optimizing the adsorption energy of the intermediate, thereby enhancing the efficiency of oxygen evolution. This work proposes a method to construct cheap and robust catalysts for practical application in energy conversion and storage.

Unraveling the Atomic-Level Manipulation Mechanism of Li2 S Redox Kinetics via Electron-Donor Doping for Designing High-Volumetric-Energy-Density, Lean-Electrolyte Lithium-Sulfur Batteries

Designing dense thick sulfur cathodes to gain high-volumetric/areal-capacity lithium-sulfur batteries (LSBs) in lean electrolytes is extremely desired. Nevertheless, the severe Li₂ S clogging and unclear mechanism seriously hinder its development. Herein, an integrated strategy is developed to manipulate Li₂ S redox kinetics of CoP/MXene catalyst via electron-donor Cu doping. Meanwhile a dense S/Cu_0.1 Co_0.9 P/MXene cathode (density = 1.95 g cm^-3 ) is constructed, which presents a large volumetric capacity of 1664 Ah L^-1 (routine electrolyte) and a high areal capacity of ≈8.3 mAh cm^-2 (lean electrolyte of 5.0 µL mg_s ^-1 ) at 0.1 C. Systematical thermodynamics, kinetics, and theoretical simulation confirm that electron-donor Cu doping induces the charge accumulation of Co atoms to form more chemical bonding with polysulfides, whereas weakens CoS bonding energy and generates abundant lattice vacancies and active sites to facilitate the diffusion and catalysis of polysulfides/Li₂ S on electrocatalyst surface, thereby decreasing the diffusion energy barrier and activation energy of Li₂ S nucleation and dissolution, boosting Li₂ S redox kinetics, and inhibiting shuttling in the dense thick sulfur cathode. This work deeply understands the atomic-level manipulation mechanism of Li₂ S redox kinetics and provides dependable principles for designing high-volumetric-energy-density, lean-electrolyte LSBs through integrating bidirectional electro-catalysts with manipulated Li₂ S redox and dense-sulfur engineering.

Monolayer CoMoS Catalysts on Hierarchically Porous Alumina Spheres as Bifunctional Nanomaterials for Hydrodesulfurization and Energy Storage Applications

In this work, CoMoS catalysts were synthesized onto porous alumina spheres obtained using Pluronic P-123 (PS) or urea (US) and used as bifunctional nanomaterials for two energy applications: hydrodesulfurization and energy storage. For the first application, the catalysts were assessed in a hydrodesulfurization reactor using two model sulfur molecules, dibenzothiophene and 4,6-dimethyl dibenzothiophene, as well as feeding a heavy oil fraction. The results indicated that the spheres obtained by Pluronic P-123 allowed a greater dispersion degree of MoS2 slabs than US, indicating that the size and hierarchically porous structure of alumina spheres played a principal role as a booster of the HDS catalytic efficiency of DBT, 4,6 DMDBT and diesel fuel. Then, these catalysts were used for the electrocatalysis of the oxygen reduction and oxygen evolution reactions (ORR/OER), which take place in rechargeable Zn-air batteries. For the ORR, the CoMoS catalyst on PS in the presence of a conductive support (N-doped carbon nanotubes + graphene) displayed an overpotential of only 90 mV in comparison with Pt/C. Importantly, the chalcogenide enabled an increase in the stability, maintaining almost two times higher current retention than Pt/C for the ORR and IrO2/C for the OER. These results suggest that expended chalcogenides from the hydrodesulfurization industry can have a second life as co-catalysts for renewable energy storage systems, enabling a circular economy.

Enabling Reversible Reaction by Uniform Distribution of Heterogeneous Intermediates on Defect-Rich SnSSe/C Layered Heterostructure for Ultralong-Cycling Sodium Storage

2D layered Sn-based materials have attracted enormous attention due to their remarkable performance in sodium-ion batteries. Nevertheless, this promising candidate involves a complex Na⁺ -storage process with multistep conversion-alloying reactions, which induces the uneven dispersion of heterogeneous intermediate accompanied by severe agglomeration of metallic Sn⁰ , inescapably resulting in poor reaction reversibility with sluggish rate capability and inferior cyclic lifespan. Herein, a delicately layered heterostructure SnSSe/C consisting of defect-rich SnSSe and graphene is designed and successfully achieved via a facile hydrothermal process. The equal anionic substitution of Se in SnSSe crystal can trigger numerous defects, which can not only facilitate Na⁺ diffusion but also accelerate the nucleation process by inducing quantum-dot-level uniform distribution of heterogeneous intermediates, Na₂ Se/Na₂ S and Sn⁰ . Concurrently, in situ formed uniform Na₂ Se/Na₂ S grain boundaries confined by this unique layered heterostructure may effectively suppress the agglomeration of metallic Sn⁰ nanograins and boost the reversibility of conversion-alloying reaction. As a result, the SnSSe/C displays significant improvement in Na-storage performance, in terms of remarkable rate capability and ultralong cycling lifespan. This work, focusing on controlling intermediate distribution, provides an effective strategy to boost reaction reversibility, which can be wildly employed in conversion-based electrodes for energy storage regions.

Hexamethylenetetramine induced multidimensional defects in Co2P nanosheets for efficient alkaline hydrogen evolution

Crystal engineering is an important way to improve the catalytic performance of transition-metal phosphides. In this work, we propose a strategy for constructing multi-dimensional defects induced by hexamethylenetetramine, which effectively introduces grain boundaries, N doping and P vacancies into Co₂P nanosheets, and improves the activity and stability of the catalyst. Due to the synergistic effect of the multi-dimensional defects, the Co₂P nanosheets exhibit excellent HER catalytic performance, especially at a large current density of 100 mA cm^-2 with an overpotential of only 159 mV. Under 1 M KOH electrolyte and current density of 10 mA cm^-2, the long-term test for 36 h shows that the catalyst maintains a very high stability.

Reaction surfaces and interfaces of metal sulfides: cryo-XPS meets HAXPES and DFT

We report here the application of the low-temperature X-ray photoelectron spectroscopy (cryo-XPS) of fast-frozen dispersions as a quasi in situ technique for a case study of metal sulfides reacted in acidic aqueous solutions under non-oxidizing and moderate oxidizing conditions. The sulfide surfaces are known to tend to be depleted in metals, producing essentially sulfur-enriched surfaces and extended underlayers on Fe- and Cu-bearing sulfides, which have previously been examined using depth-sensitive HAXPES and cryo-XPS. The current study is focused on zinc and lead sulfides (natural sphalerite and galena), for whom both the experiment and theoretical DFT simulations suggest a low stability of sulfur-excessive structures. Cryo-XPS revealed the complicated behavior of the minerals under non-oxidative etching conditions, in particular, a notable concentration of polysulfide for PbS in dilute perchloric acid and a very minor one in hydrochloric acid. Oxidative etching with Fe³⁺ cations produced polysulfide anions and then elemental sulfur, which both volatized in the ultra-high vacuum at room temperature; the species can, nonetheless, be distinguished by considering the binding energies, electrostatic charging and evaporation rates. The cryo-XPS also detected interfacial products, e.g., ferrous chloride. DFT found that S-excessive centers are unstable in the undersurface regions of both materials, but are less unfavorable for ZnS surfaces, in agreement with the experimental data. It was concluded that cryo-XPS allows us to greatly reduce distortions of the interface composition in comparison with conventional techniques.

Synergistic effects of B/S co-doped spongy-like hierarchically porous carbon for a high performance zinc-ion hybrid capacitor

Zinc-ion hybrid capacitors (ZIHCs) are regarded as a potential candidate for large-scale energy storage devices. However, the inadequate cathode and the inferior wettability between the electrode and electrolyte hinder the construction of high-performance ZIHCs. Herein, boron (B) and sulfur (S) co-doped spongy-like hierarchically porous carbon (B₂S₃C) is first proposed as a cathode material for ZIHCs. Here, B doping is favorable for improving the wettability, while S doping contributes to enhancing the electrical properties. In addition, the density functional theory (DFT) results uncover that B and S atoms contribute to reducing the energy barrier between Zn²⁺ and the cathode, leading to boosted chemical adsorption ability of Zn²⁺ on the cathode. As a result, the assembled ZIHC based on B₂S₃C exhibits a high specific capacity of 182.6 mA h g^-1 at 0.1 A g^-1, an excellent capacity retention of 96.2% after 10 000 cycles and a remarkable energy density of 292.2 W h kg^-1 at a power density of 62.2 W kg^-1, superior to the previously reported ZIHCs. Due to the flexibility of the assembled electrodes, the solid-state ZIHC can sustain various deformations. This work paves a feasible path for the development of cost-effective and high-performance porous carbon materials.

Synergistic Effect of the Sulfur Vacancy and Schottky Heterojunction on Photocatalytic Uranium Immobilization: The Thermodynamics and Kinetics

Not only a critical matter in the nuclear fuel cycle but uranium is also a global contaminant with both radioactive and chemical toxicity. Reducing soluble hexavalent uranium [U(VI)] to relatively nonimmigrated tetravalent uranium [U(IV)] by photocatalytic technologies is recognized as a highly promising strategy for avoiding environmental pollution and re-extracting uranium resources from nuclear wastewater. Herein, we have designed a heterojunction photocatalyst constructed from the carbon aerogels (CA) and the CdS nanoflowers with an S-vacancy (CA@CdS-SV). With the S-vacancy and heterojunction being synergized, the U(VI) removal rate exceeded 97% in 40 min without the addition of any sacrificial agents. As impacted by the synergistic effects of the S-vacancy and heterojunction, thermodynamics and kinetics revealed that photogenerated electrons were first captured via shallow traps generated by vacancies on CdS-SV and then transferred to the CA surfaces through the heterojunction to realize the spatial separation of carriers, thereby achieving a satisfactory performance. This work is considered to underpin the improvement of U(VI) immobilization by exploiting the synergistic effect of vacancy engineering and the Schottky heterojunction from the perspective of thermodynamics and kinetics.

MOF-Derived ZnS/NC yolk-shell Composites for Highly Reversible Lithium Storage

The application of ZnS-based anode materials in lithium-ion batteries (LIBs) has some severe challenges, such as the insulating nature of ZnS, the pronounced polarization caused by conversion reactions and alloying...

Electronic regulation of a core–shell NiSe2 catalyst by Co doping to accelerate hydrogen evolution

A Co-doping core–shell shaped NiSe2 based catalyst (NixCo1−xSe2@NC) exhibits promising electrocatalytic activity for HER with a low overpotential of −143 mV at −10 mA cm−2, a small Tafel slope of 37.5 mV dec−1.

Advancing Photoelectrochemical Energy Conversion through Atomic Design of Catalysts

Powered by inexhaustible solar energy, photoelectrochemical (PEC) hydrogen/ammonia production and reduction of carbon dioxide to high added-value chemicals in eco-friendly and mild conditions provide a highly attractive solution to carbon neutrality. Recently, substantial advances have been achieved in PEC systems by improving light absorption and charge separation/transfer in PEC devices. However, less attention is given to the atomic design of photoelectrocatalysts to facilitate the final catalytic reactions occurring at photoelectrode surface, which largely limits the overall photo-to-energy conversion of PEC system. Fundamental catalytic mechanisms and recent progress in atomic design of PEC materials are comprehensively reviewed by engineering of defect, dopant, facet, strain, and single atom to enhance the activity and selectivity. Finally, the emerging challenges and research directions in design of PEC systems for future photo-to-energy conversions are proposed.