二维黑磷基纳米材料在光催化中的应用

黑磷是继石墨烯之后又一种新型的单元素二维材料。具有独特的层状结构、超高的载流子迁移率和由层厚调控的禁带宽度,在光催化领域具有广阔的应用前景。然而,单一黑磷材料的禁带宽度较窄( ≤ 1.5 eV),光生载流子极易复合,导致其光催化性能较低。另外,黑磷表面的磷原子易与环境中的氧气发生反应形成P_xO_y,降低了黑磷材料的稳定性。因此,较低的催化性能和不稳定性极大地限制了黑磷材料的实际应用。针对上述问题,可以通过将黑磷材料与其他材料复合形成一系列的等离子体复合材料和多维异质结的方式,来提高光催化剂的活性和循环稳定性。本文综述了近年来二维黑磷纳米片与金属、半导体和碳材料等复合后形成的复合材料在光催化裂解水产氢、降解有机污染物、CO₂还原和固氮等方面的研究进展。最后,对未来二维黑磷基光催化材料的研究方向进行了分析和展望。     

半导体氧化物光催化裂解水制氢

本文综述了半导体氧化物光催化裂解水制氢的反应机理,以及近年来半导体光催化裂解水制氢的研究进展。讨论了各种因素对材料光催化性能的影响以及改性方法,并对今后的研究方向提出了一些建议。     

半导体氧化物光催化裂解水制氢

本文综述了半导体氧化物光催化裂解水制氢的反应机理,以及近年来半导体光催化裂解水制氢的研究进展。讨论了各种因素对材料光催化性能的影响以及改性方法,并对今后的研究方向提出了一些建议。     

Considerations for a More Accurate Evaluation Method for Photocatalytic Water Splitting

Over the past decades, various photocatalysts have been developed and great progress has been achieved in the field of solar-driven photocatalytic water splitting. However, the lack of an accurate and comprehensive evaluation method greatly hinders the meaningful comparison between different systems and becomes a serious impediment for the development of photocatalysts. Although many researchers are aware of this, there has been little work in this area. In this Viewpoint, we first analyze the insufficiencies of the existing evaluation methods and then make preliminary suggestions, aiming to stimulate discussion in the research community and hopefully lead to a widely accepted and authoritative evaluation system to assess photocatalyst performance.     

Photocatalytic Water Splitting Under Visible Light with Particulate Semiconductor Catalysts

Photocatalytic water splitting (PWS) is the most promising technology to produce H₂ energy directly from renewable water and solar light. PWS has made a remarkable progress last decades under ultra-violet (UV) light, but there are many technical challenges remaining for PWS under visible light. Several approaches are taken in search of photocatalysts efficient for PWS under visible light: (i) to find new single phase materials, (ii) to decorate UV-active photocatalysts with a photosensitizer absorbing visible light, (iii) to tune the band gap energy by modifying cations or anions of UV-active photocatalysts with substitutional doping, and (iv) to fabricate multi-component photocatalysts by forming composites or solid solutions. This article discusses the above approaches based on our experimental results as well as data available in the literature. At the moment, the greatest challenge to the progress of visible light PWS is the low efficiency of light utilization. Finding new photocatalytic materials with unique structure and phase is still the key to the success. In addition, the synthesis of these materials with high crystallinity and high surface area is also important, because these properties exert great impact on the activity of the material of the same structure and phase. Finally, smart combination and modification of known materials could also be fruitful.     

Alloyed ZnS–CuInS2 Semiconductor Nanorods and Their Nanoscale Heterostructures for Visible‐Light‐Driven Photocatalytic Hydrogen Generation

A promising photocatalytic system in the form of heterostructured nanocrystals (HNCs) is presented wherein alloyed ZnS–CuInS₂ (ZCIS) semiconductor nanorods are decorated with Pt and Pd₄S nanoparticles. This is apparently the first report on the colloidal preparation and photocatalytic behavior of ZCIS–Pt and ZCIS–Pd₄S nanoscale heterostructures. Incorporation of Pt and Pd₄S cocatalysts leads to considerable enhancement of the photocatalytic activity of ZCIS for visible‐light‐driven hydrogen production.     

Z‐Scheme Photocatalytic Water Splitting on a 2D Heterostructure of Black Phosphorus/Bismuth Vanadate Using Visible Light

Spontaneously solar‐driven water splitting to produce H₂ and O₂, that is, the conversion of solar energy to chemical energy is a dream of mankind. However, it is difficult to make overall water splitting feasible without using any sacrificial agents and external bias. Drawing inspiration from nature, a new artificial Z‐scheme photocatalytic system has been designed herein based on the two‐dimensional (2D) heterostructure of black phosphorus (BP)/bismuth vanadate (BiVO₄). An effective charge separation makes possible the reduction and oxidation of water on BP and BiVO₄, respectively. The optimum H₂ and O₂ production rates on BP/BiVO₄ were approximately 160 and 102 μmol g^?1 h^?1 under irradiation of light with a wavelength longer than 420 nm, without using any sacrificial agents or external bias.     

A Hydrogen‐Deficient Nickel–Cobalt Double Hydroxide for Photocatalytic Overall Water Splitting

Developing highly efficient and low‐cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel–cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble‐metal co‐catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so‐called L‐NiCo nanosheets with a nonstoichiometric composition and O^2?/Co³⁺ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O^2? and Co³⁺ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H₂ evolution rate of 1.7 μmol h^?1 under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.     

Intercalation of Highly Dispersed Metal Nanoclusters into a Layered Metal Oxide for Photocatalytic Overall Water Splitting

Metal nanoclusters (involving metals such as platinum) with a diameter smaller than 1 nm were deposited on the interlayer nanospace of KCa₂Nb₃O₁₀ using the electrostatic attraction between a cationic metal complex (e.g., [Pt(NH₃)₄]Cl₂) and a negatively charged two‐dimensional Ca₂Nb₃O₁₀^? sheet, without the aid of any additional reagent. The material obtained possessed eight‐fold greater photocatalytic activity for water splitting into H₂ and O₂ under band‐gap irradiation than the previously reported analog using a RuO₂ promoter. This study highlighted the superior functionality of Pt nanoclusters with diameters smaller than 1 nm for photocatalytic overall water splitting. This material shows the greatest efficiency among nanosheet‐based photocatalysts reported to date.     

Control of Spatially Homogeneous Distribution of Heteroatoms to Produce Red TiO2 Photocatalyst for Visible-Light Photocatalytic Water Splitting

The strong band-to-band absorption of photocatalysts spanning the whole visible-light region (400–700 nm) is critically important for solar-driven photocatalysis. Although it has been actively and widely used as a photocatalyst for various reactions in the past four decades, TiO₂ has a very poor ability to capture the whole spectrum of visible light. In this work, by controlling the spatially homogeneous distribution of boron and nitrogen heteroatoms in anatase TiO₂ microspheres with a predominance of high-energy {001} facets, a strong visible-light absorption spectrum with a sharp edge beyond 680 nm has been achieved. The red TiO₂ obtained with homogeneous doping of boron and nitrogen shows no increase in defects like Ti³⁺ that are commonly observed in doped TiO₂. More importantly, it has the ability to induce photocatalytic water oxidation to produce oxygen under the irradiation of visible light beyond 550 nm and also the photocatalytic reduction of water to produce hydrogen under visible light. These results demonstrate the great promise of using red TiO₂ for visible-light photocatalytic water splitting and also reveal an attractive strategy for realizing the wide-spectrum visible-light absorption of wide-band-gap oxide photocatalysts.     

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.     

还原氧化石墨烯/介孔TiO2复合材料的合成及其光解水制氢性能

采用溶胶凝胶法,以钛酸四异丙酯(TTIP)为钛源,十六烷基三甲基溴化铵(CTAB)为模板剂合成了介孔二氧化钛样品mTiO_2,考察了合成温度、水量、模板剂用量和焙烧温度对其在紫外光条件下光催化产氢活性的影响。结果显示,在350℃下焙烧后,样品由无定形结构转变为锐钛矿相;随着焙烧温度的提高,锐钛矿相结构产物的结晶度提高,当焙烧温度超过550℃后,样品大部分转变为金红石相。以合成温度为30℃,模板剂用量(nCTAB/nTiO_2)为0.2,水量(nH2O/nTiO_2)为100,焙烧温度为450℃条件下合成的m-TiO_2样品为催化剂,当催化剂用量为0.4 g·L-1,体系中甲醇浓度高于20%(V/V)时,其紫外光条件下的光催化产氢活性达170 mmol·g-1·h-1。采用水热法将氧化石墨烯(GO)与m-TiO_2复合制备了一系列还原氧化石墨烯/介孔TiO_2复合材料(rGO/m-TiO_2),其晶相结构为锐钛矿相。当r GO复合量(wGO/wTiO_2)为0.01时,样品在紫外光下的产氢活性为241 mmol·g-1·h-1,能量转化效率达7.4%,较未复合样品提高了42.3%;在可见光条件下,其产氢活性达9 mmol·g-1·h-1。     

Surface Plasmon Resonance‐Enhanced Visible‐NIR‐Driven Photocatalytic and Photothermal Catalytic Performance by Ag/Mesoporous Black TiO2 Nanotube Heterojunctions

Ag/mesoporous black TiO₂ nanotubes heterojunctions (Ag‐MBTHs) were fabricated through a surface hydrogenation, wet‐impregnation and photoreduction strategy. The as‐prepared Ag‐MBTHs possess a relatively high specific surface area of ≈85 m² g^?1 and an average pore size of ≈13.2 nm. The Ag‐MBTHs with a narrow band gap of ≈2.63 eV extend the photoresponse from UV to the visible‐light and near‐infrared (NIR) region. They exhibit excellent visible‐NIR‐driven photothermal catalytic and photocatalytic performance for complete conversion of nitro aromatic compounds (100 %) and mineralization of highly toxic phenol (100 %). The enhancement can be attributed to the mesoporous hollow structures increasing the light multi‐refraction, the Ti³⁺ in frameworks and the surface plasmon resonance (SPR) effect of plasmonic Ag nanoparticles favoring light‐harvesting and spatial separation of photogenerated electron–hole pairs, which is confirmed by transient fluorescence. The fabrication of this SPR‐enhanced visible‐NIR‐driven Ag‐MBTHs catalyst may provide new insights for designing other high‐performance heterojunctions as photocatalytic and photothermal catalytic nanomaterials.     

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.     

Intrinsic Facet‐Dependent Reactivity of Well‐Defined BiOBr Nanosheets on Photocatalytic Water Splitting

Surface atomic arrangement and coordination of photocatalysts highly exposed to different crystal facets significantly affect the photoreactivity. However, controversies on the true photoreactivity of a specific facet in heterogeneous photocatalysis still exits. Herein, we exemplified well‐defined BiOBr nanosheets dominating with respective facets, (001) and (010), to track the reactivity of crystal facets for photocatalytic water splitting. The real photoreactivity of BiOBr‐(001) were evidenced to be significantly higher than BiOBr‐(010) for both hydrogen production and oxygen evolution reactions. Further in situ photochemical probing studies verified the distinct reactivity is not only owing to the highly exposed facets, but dominated by the co‐exposing facets, leading to an efficient spatial separation of photogenerated charges and further making the oxidation and reduction reactions separately occur with different reaction rates, which ordains the fate of the true photoreactivity.