黑色氮化钨作为金属性光催化剂实现全分解水

正光解水技术可以将太阳能转换存储为化学能,被视为解决全球性能源与环境问题的理想方式之一~(1,2)。太阳能转换效率一定程度上取决于光催化材料的吸光范围,然而考虑到最小禁带宽度1.23 e V和光解水过程中可能存在的能量损失等因素,单一半导体实现全分解水的吸光范围较难超过700 nm。目前已报道的半导体光催化材料实现全分解水的最长响应波长是600 nm~3。具有金属性的光催化剂依靠带内跃迁来产生电子空穴对的这一特点,有可能使其突破700 nm波长光响应这     

Photocatalyst Materials for Water Splitting

Various photocatalyst materials developed by the group of the present author are described. Alkali and alkaline earth tantalates have arisen as a new group of photocatalyst materials for splitting of water into H₂ and O₂ under ultraviolet irradiation. They showed activities even without co-catalysts such as Pt, being different from titanate photocatalysts. When NiO co-catalysts were loaded on the tantalate photocatalysts, the photocatalytic activities were markedly increased. Among the tantalates, NiO/NaTaO₃ doped with La showed the highest activity. BiVO₄, AgNO₃, and TiO₂ co-doped with Cr and Sb photocatalysts showed high activities for O₂ evolution in the presence of a sacrificial reagent (Ag⁺) under visible light irradiation ( > 420 nm). Pt/SrTiO₃ co-doped with Cr and Sb or Ta, Pt/NaInS₂, and Pt/AgInZn₇S₉ photocatalysts showed high activities for H₂ evolution from aqueous solutions containing reducing reagents under visible light irradiation. Furthermore, Cu- or Ni-doped ZnS photocatalysts showed H₂ evolution activities even without co-catalysts such as Pt.     

CoxP/Hollow Porous C3N4 as Highly Efficient Schottky Contact Photocatalyst for H2 Evolution from Water Splitting

Photocatalytic water splitting to obtain hydrogen energy can transform low-density solar to high density, new and clean energy in a clean way, which is one of the ideal ways to solve the energy crisis and environmental pollution. In this paper, The Co_xP/hollow porous C₃N₄ composite photocatalytic material was synthesized by simple methods. The photocatalytic hydrogen production rate of Co_xP/hollow porous C₃N₄ reaches 1602 μmol g⁻¹ h⁻¹, which is 151 times of that of pure C₃N₄. The reasons for the high photocatalytic H₂ evolution activity of Co_xP/hollow porous C₃N₄ could be summarized as follows: (1) the hollow and porous structure of C₃N₄ shows higher light capture efficiency, larger specific surface area and more surface active sites. (2) metalloid Co_xP loaded forms the Schottky contact with C₃N₄, which improves the photogenerated charges separation efficiency of C₃N₄, prolongs the photogenerated charges lifetime and improves the photocatalytic H₂ evolution activity of C₃N₄. (3) The higher conductivity of metalloid Co_xP and the lower overpotential of hydrogen production are other reasons for the higher activity of photocatalytic hydrogen production of Co_xP/hollow porous C₃N₄. This work provides an important role for the design of efficient, stable, and efficient construction of photocatalysts for solar energy conversion.     

Mimicking Photosynthesis: A Natural Z-Scheme Photocatalyst Constructed from Red Mud Bauxite Waste for Overall Water Splitting

All-solid-state Z-Scheme photocatalysts have attracted significant attention due to their great potential for solar fuel production. However, delicately coupling two individual semiconductors with a charge shuttle by a material strategy remains a challenge. Herein, we demonstrate a new protocol of natural Z-Scheme heterostructures by strategically engineering the component and interfacial structure of red mud bauxite waste. Advanced characterizations elucidated that the hydrogen-induced formation of metallic Fe enabled the effective Z-Scheme electron transfer from γ-Fe₂O₃ to TiO₂, leading to the significantly boosted spatial separation of photo-generated carriers for overall water splitting. To the best of our knowledge, it is the first Z-Scheme heterojunction based on natural minerals for solar fuel production. Thus our work provides a new avenue toward the utilization of natural minerals for advanced catalysis applications.     

Inorganic Photocatalysts for Overall Water Splitting

Photocatalytic water splitting using semiconductor photocatalysts has been considered as a “green” process for converting solar energy into hydrogen. The pioneering work on electrochemical photolysis of water at TiO₂ electrode, reported by Fujishima and Honda in 1972, ushered in the area of solar fuel. As the real ultimate solution for solar fuel‐generation, overall water splitting has attracted interest from researchers for some time, and a variety of inorganic photocatalysts have been developed to meet the challenge of this dream reaction. To date, high‐efficiency hydrogen production from pure water without the assistance of sacrificial reagents remains an open challenge. In this Focus Review, we aim to provide a whole picture of overall water splitting and give an outlook for future research.     

Two-Dimensional GaTe/Bi2Se3 Heterostructure: a Promising Direct Z-scheme Water Splitting Photocatalyst

Among various photocatalytic materials, Z-scheme photocatalysts have drawn tremendous research interest due to high photocatalytic performance in solar water splitting. Here, we perform extensive hybrid density functional theory calculations to explore electronic structures, interfacial charge transfer, electrostatic potential profile, optical absorption properties, and photocatalytic properties of a proposed two-dimensional (2D) small-lattice-mismatched GaTe/Bi\begin{document}$ _2 $\end{document}Se\begin{document}$ _3 $\end{document} heterostructure. Theoretical results clearly reveal that the examined heterostructure with a small direct band gap can effectively harvest the broad spectrum of the incoming sunlight. Due to the relative strong interfacial built-in electric field in the heterostructure and the small band gap between the valence band maximum of GaTe monolayer and the conduction band minimum of Bi\begin{document}$ _2 $\end{document}Se\begin{document}$ _3 $\end{document} nanosheet with slight band edge bending, these photogenerated carriers transfer via Z-scheme pathway, which results in the photogenerated electrons and holes effectively separating into the GaTe monolayer and the Bi\begin{document}$ _2 $\end{document}Se\begin{document}$ _3 $\end{document} nanosheet for the hydrogen and oxygen evolution reactions, respectively. Our results imply that the artificial 2D GaTe/Bi\begin{document}$ _2 $\end{document}Se\begin{document}$ _3 $\end{document} is a promising Z-scheme photocatalyst for overall solar water splitting.     

Coupling of Bifunctional CoMn‐Layered Double Hydroxide@Graphitic C3N4 Nanohybrids towards Efficient Photoelectrochemical Overall Water Splitting

The development of durable, low‐cost, and efficient photo‐/electrolysis for the oxygen and hydrogen evolution reactions (OER and HER) is important to fulfill increasing energy requirements. Herein, highly efficient and active photo‐/electrochemical catalysts, that is, CoMn‐LDH@g‐C₃N₄ hybrids, have been synthesized successfully through a facile in situ co‐precipitation method at room temperature. The CoMn‐LDH@g‐C₃N₄ composite exhibits an obvious OER electrocatalytic performance with a current density of 40 mA cm^?2 at an overpotential of 350 mV for water oxidation, which is 2.5 times higher than pure CoMn‐LDH nanosheets. For HER, CoMn‐LDH@g‐C₃N₄ (η₅₀=?448 mV) requires a potential close to Pt/C (η₅₀=?416 mV) to reach a current density of 50 mA cm². Furthermore, under visible‐light irradiation, the photocurrent density of the CoMn‐LDH@g‐C₃N₄ composite is 0.227 mA cm^?2, which is 2.1 and 3.8 time higher than pristine CoMn‐LDH (0.108 mA cm^?2) and g‐C₃N₄ (0.061 mA cm^?2), respectively. The CoMn‐LDH@g‐C₃N₄ composite delivers a current density of 10 mA cm^?2 at 1.56 V and 100 mA cm^?2 at 1.82 V for the overall water‐splitting reaction. Therefore, this work establishes the first example of pure CoMn‐LDH and CoMn‐LDH@g‐C₃N₄ hybrids as electrochemical and photoelectrochemical water‐splitting systems for both OER and HER, which may open a pathway to develop and explore other LDH and g‐C₃N₄ nanosheets as efficient catalysts for renewable energy applications.     

Graphene-Based Nanomaterials for Solar-Driven Overall Water Splitting

Water splitting through photocatalysis and photoelectrochemical methods is a promising strategy for solar energy utilization. Graphene is widely used in solar-driven overall water splitting because of its versatile properties. This review summarizes the preparation of graphene-based photocatalysts and photoelectrodes and the functions of graphene, and highlights the challenges and prospects of the future applications of graphene in solar-driven water splitting.     

Overall Water Splitting on the Transition‐Metal Oxynitride Photocatalyst LaMg1/3Ta2/3O2N over a Large Portion of the Visible‐Light Spectrum

One of the main targets of studies on water splitting photocatalysts is to develop semiconductor materials with narrower bandgaps capable of overall water splitting for efficient harvesting of solar energy. A series of transition‐metal oxynitrides, LaMg_xTa_1?xO_1+3xN_2?3x (x≥1/3), with a complex perovskite structure was reported as the first example of overall water splitting operable at up to 600 nm. The photocatalytic behavior of LaMg_1/3Ta_2/3O₂N was investigated in detail in order to optimize photocatalyst preparation and water‐splitting activity. Various attempts exploring photocatalyst preparation steps, that is, cocatalyst selection, coating material and method, and synthesis method for the oxide precursor, revealed photocatalyst structures necessary for achieving overall water splitting. Careful examination of photocatalyst preparation procedures likely enhanced the quality of the produced photocatalyst, leading to a more homogeneous coating quality and semiconductor particles with fewer defects. Thus, the photocatalytic activity for water splitting on LaMg_1/3Ta_2/3O₂N was largely enhanced.     

Hydrothermal Synthesized Co-Ni3S2 Ultrathin Nanosheets for Efficient and Enhanced Overall Water Splitting

We used the one-step hydrothennal controlled synthesis method for Co-Ni3S2 ultrathin nanosheets grown directly on nickel foam(NF).The as-synthesized Co-Ni3S2/NF showed eiilianced activities in the hydrogen evolution reaction(HER),oxygen evolution reaction(OER)and better overall water splitting(OWS)efficiency than the iin-doped Ni3S2/NF.the voltage of Co-Ni3S2/NF for OWS was only 1.58 V at the current density of 10 niA/cm^2 and with long time(>30 h)current output during the current-density(i-t)test.The good i-t pertonnance was also observed in both HER and OER processes.Additionally,the Co-Ni3S2/NF showed a large current density(>1A/cm^2)for both HER and OER.Wlien the current densities reached 100 and 1000 mA/cm^2,the required overpotentials tor Co-Ni3S2/NF were 0.35 and 0.75 V for OER and 0.30 and 0.85 V for HER.Therefore,after introducing Co,the activity of Ni3S2-based material was strongly enhanced.     

可见光响应光催化剂BiYWO6的制备、表征及其完全分解水的研究

制备了一种可见光响应的光催化剂BiYWO6, 该体系是Bi2WO6-Y2WO6的伪二元固溶体, 其禁带宽度为2.71 eV. 其负载了助催化剂后, 可在紫外光和可见光下完全分解水生成氢气和氧气, 其中负载RuO2助催化剂的BiYWO6具有最好的光催化活性. 通过对光催化反应前后的BiYWO6和助催化剂的表面各元素的化学状态的研究证实了RuO2/BiYWO6体系的稳定性. 比较分析了BiYWO6的能带结构, 认为可见光完全分解水的性能可归因于Y和Bi在固溶体BiYWO6中形成了合适的能带结构.     

Single‐Site Active Cobalt‐Based Photocatalyst with a Long Carrier Lifetime for Spontaneous Overall Water Splitting

An active and stable photocatalyst to directly split water is desirable for solar‐energy conversion. However, it is difficult to accomplish overall water splitting without sacrificial electron donors. Herein, we demonstrate a strategy via constructing a single site to simultaneously promote charge separation and catalytic activity for robust overall water splitting. A single Co₁‐P₄ site confined on g‐C₃N₄ nanosheets was prepared by a facile phosphidation method, and identified by electron microscopy and X‐ray absorption spectroscopy. This coordinatively unsaturated Co site can effectively suppress charge recombination and prolong carrier lifetime by about 20 times relative to pristine g‐C₃N₄, and boost water molecular adsorption and activation for oxygen evolution. This single‐site photocatalyst exhibits steady and high water splitting activity with H₂ evolution rate up to 410.3 μmol h⁻¹ g⁻¹, and quantum efficiency as high as 2.2 % at 500 nm.     

A Flexible Electrode Based on Iron Phosphide Nanotubes for Overall Water Splitting

The design of cheap and efficient water splitting systems for sustainable hydrogen production has attracted increasing attention. A flexible electrode, based on carbon cloth substrate and iron phosphide nanotubes coated with an iron oxide/phosphate layer, is shown to catalyze overall water splitting. The as‐prepared flexible electrode demonstrates remarkable electrocatalytic activity for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) at modest overpotentials. The surface iron oxide/phosphate, which is formed in situ, is proposed to improve the HER activity by facilitating the water‐dissociation step and serves directly as the catalytically‐active component for the OER process.     

Black Tungsten Nitride as a Metallic Photocatalyst for Overall Water Splitting Operable at up to 765 nm

Semiconductor photocatalysts are hardly employed for overall water splitting beyond 700 nm, which is due to both thermodynamic aspects and activation barriers. Metallic materials as photocatalysts are known to overcome this limitation through interband transitions for creating electron–hole pairs; however, the application of metallic photocatalysts for overall water splitting has never been fulfilled. Black tungsten nitride is now employed as a metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm. Experimental and theoretical results together confirm that metallic properties play a substantial role in exhibiting photocatalytic activity under red‐light irradiation for tungsten nitride. This work represents the first red‐light responsive photocatalyst for overall water splitting, and may open a promising venue in searching of metallic materials as efficient photocatalysts for solar energy utilization.     

Hollow Bimetallic Zinc Cobalt Phosphosulfides for Efficient Overall Water Splitting

Bimetallic sulfides with earth-abundant transition-metal elements are proposed to enhance the electrocatalytic activities. Further replacement of S atom by less electronegative P atom improves the electrocatalytic performance of OER and HER. Herein, hollow bimetallic zinc cobalt phosphosulfides (Zn_0.3Co_2.7S₃P) are synthesized by a two-step process. The optimal catalyst of Zn_0.3Co_2.7S₃P with particle size of 50 nm displays an excellent electroactivity and long-term durability toward efficient overall water splitting process in alkaline medium. The excellent bifunctional electrocatalytic performance may be ascribed to the synergistic effect of hollow structure, anion substitution tuning and unique size control.     

可见光“全”分解水的类纳光电化学(PEC)电池模型

本文在对新型TiO2的光、电性质和形貌学研究基础上,首次提出"可见光‘全’分解水的类纳PEC电池模型",将水的redox反应分别放在新型TiO2纳米管内、外表面上进行。模型还提出以合适电化学性质的可变价金属氧化物作为放氧催化剂,表面晶格氧参与放O2过程,克服"全"光解水中四电子转移放O2的困难。此模型期望更多同行进行探索、验证。     

Oxysulfide Semiconductors for Photocatalytic Overall Water Splitting with Visible Light

Photocatalytic overall water splitting by sulfide‐based materials is a great challenge because of the poor resilience of such materials against hole oxidation. In a recent study, Domen and co‐workers developed an innovative strategy to stabilize sulfide‐based photocatalysts by hybridizing S 3p with O 2p orbitals to produce oxysulfides in which S^2? is stable. Further surface engineering of the oxysulfides with dual co‐catalysts promoted charge separation and interface transfer, thus reducing the charge build‐up that inhibits photocorrosion. The pH value of the reaction mixture is a critical consideration for achieving efficient stoichiometric H₂ and O₂ evolution by these oxysulfide photocatalysts.