基于多金属氧酸盐催化剂的光驱动产氢研究进展

能源和环境问题是21世纪人类面临的两个巨大挑战.鉴于此,为了实现人类社会的可持续发展,寻求能够替代化石能源的安全无污染可再生能源已迫在眉睫.太阳光驱动水分解是实现太阳能转化生产清洁可再生氢能的理想方法,其分解产物氢气和氧气在燃烧释放能量的同时生成洁净无污染的可饮用水,实现了完美的可持续能量循环,对于解决当今全球面临的能源危机与环境污染问题具有巨大的应用价值.然而,长期以来光驱动水分解所面临的巨大难题是半反应动力学非常缓慢,通常需要克服较高的能量势垒,导致整体能量转化效率低.利用非贵金属制备高催化效能、低成本的水分解催化材料成为该领域的研究热点和难点.目前,已报道的光驱动产氢催化剂可以被归纳为两大类:均相催化剂和异相催化剂.均相催化剂通常具备高催化活性、高选择性以及易于进行机理研究等优点,而异相催化剂则具备廉价、易得和高稳定性等优点;然而它们也存在一些不容忽视的问题,如均相催化剂的低稳定性、易分解失活,异相催化剂表面易被毒化失活、低催化转化数及转化频率等.如何设计合成兼具二者优点的产氢催化剂吸引了领域内研究者的广泛关注.作为一类新兴的多电子转移催化剂,多金属氧酸盐因其丰富多样的合成策略以及高度可调的物理化学及光化学性质,已被广泛用于催化水分解制氢气研究.该类多金属氧酸盐催化剂具备了介于均相分子化合物和异相金属氧化物之间的结构,这种独特的结构赋予它们同时具备均相分子催化剂的高活性、高选择性、高可控性、易于进行机理性研究等优点,又具备异相金属氧化物催化剂的廉价易得及稳定性高等优势.随着研究的开展,基于多金属氧酸盐的光催化产氢体系已由当初的贵金属辅助逐渐转变为丰产元素参与,光源的选择方面也从与太阳光谱匹配度低的紫外光转变为可见光.本文对30多年来基于多金属氧酸盐催化剂的光驱动产氢成果进行了综述,主要包括有/无贵金属辅助的多金属氧酸盐,多酸@金属有机框架复合物,多酸-半导体复合材料在紫外光或可见光条件下的光催化产氢研究;同时讨论总结了不同类型催化体系的反应机理;并对该领域的未来发展趋势及研究方向进行了展望.     

Light-driven hydrogen production by a hybrid complex of a [NiFe]-hydrogenase and the cyanobacterial photosystem I

In order to generate renewable and clean fuels, increasing efforts are focused on the exploitation of photosynthetic microorganisms for the production of molecular hydrogen from water and light. In this study we engineered a 'hard-wired' protein complex consisting of a hydrogenase and photosystem I (hydrogenase-PSI complex) as a direct light-to-hydrogen conversion system. The key component was an artificial fusion protein composed of the membrane-bound [NiFe] hydrogenase from the beta-proteobacterium Ralstonia eutropha H16 and the peripheral PSI subunit PsaE of the cyanobacterium Thermosynechococcus elongatus. The resulting hydrogenase-PsaE fusion protein associated with PsaE-free PSI spontaneously, thereby forming a hydrogenase-PSI complex as confirmed by sucrose-gradient ultracentrifuge and immunoblot analysis. The hydrogenase-PSI complex displayed light-driven hydrogen production at a rate of 0.58 mumol H(2).mg chlorophyll(-1).h(-1). The complex maintained its accessibility to the native electron acceptor ferredoxin. This study provides the first example of a light-driven enzymatic reaction by an artificial complex between a redox enzyme and photosystem I and represents an important step on the way to design a photosynthetic organism that efficiently converts solar energy and water into hydrogen.     

A mechanism for water splitting and hydrogen absorbing functions of metal–oxide layered hydrogen storage materials studied by means of ion beam analysis

This review describes a study of catalytic functions of water splitting at the surface and hydrogen gas emitting from the bulk of metal–oxide layered materials as well as hydrogen storage materials as its application by means of the ion beam analysis techniques. First are described a microscopic model for water splitting at the oxide surface and mass balance equations for hydrogen atoms in the bulk. The latter is a mathematical expression of a one‐way diffusion model proposed for an anomalous isotope effect in D–H and H–D replacements of both deuterium (D) implanted into perovskite oxide ceramics by protium (H) in H₂O vapour and the vise versa. The latter model brings about finding of catalytic functions of water splitting at the surface and hydrogen gas emitting from the bulk. Second, experimental results on the anomalous isotope effect are presented and the D–H replacement rates are described in detail. Subsequently are shown results on H₂ gas emission measured with a Bach method, which give a clear evidence for the water splitting and hydrogen gas emitting catalytic functions of the oxide surface. Finally, we present experimental data on the hydrogen absorption and emission characteristics of the metal–oxide layered hydrogen storage materials as an application of the water splitting and hydrogen absorbing catalysts. Copyright © 2014 John Wiley & Sons, Ltd.     

基于立方烷结构的分子催化剂在光催化水氧化中的研究进展

随着化石燃料大量使用带来的气候变化和环境污染问题日趋严重,寻找清洁高效的可再生能源用做传统化石燃料的替代品,已经成为当前的研究热点。光驱动的水分解反应被认为是太阳能制氢的可行途径。水的全分解包括两个半反应-水的氧化和质子还原。其中水的氧化反应是一个涉及四个电子和四个质子转移的复杂过程,需要很高的活化能,被认为是全分解水反应的瓶颈步骤。因此,开发高效、稳定、廉价丰产的水氧化催化剂是人工光合作用突破的关键因素。立方烷具有类似自然界光合作用酶光系统II(PSII)活性中心Mn_4CaO_5簇的结构,世界各国的科学家受自然界光合作用的启发,开发出了许多基于过渡金属的立方烷结构的催化剂,常见的有锰、钴和铜等立方烷催化剂。本文简要地综述了近年来立方烷分子催化剂在光催化水氧化中的研究进展。首先介绍了立方烷基光催化水氧化反应历程,继而详细介绍了基于有机配体的立方烷配合物和全无机的多金属氧酸盐立方烷水氧化催化剂,其次是半导体(BiVO4或聚合的氮化碳(PCN))为捕光材料复合立方烷分子催化剂的水氧化体系最新研究进展。最后总结并展望了该领域所面临的挑战及其前景。     

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.     

Rethinking Electronic Effects in Photochemical Hydrogen Evolution Using CuInS2@ZnS Quantum Dots Sensitizers

Molecular catalysts based on coordination complexes for the generation of hydrogen via photochemical water splitting exhibit a large versatility and tunability of the catalytic properties through chemical functionalization. In the present work, we report on light-driven hydrogen production in an aqueous solution using a series of cobalt polypyridine complexes as hydrogen evolving catalysts (HECs) in combination with CuInS₂@ZnS quantum dots (QDs) as sensitizers, and ascorbate as the electron donor. A peculiar trend in activity has been observed depending on the substituents present on the polypyridine ligand. This trend markedly differs from that previously recorded using [Ru(bpy)₃]²⁺ (where bpy = 2,2’-bipyridine) as the sensitizer and can be ascribed to different kinetically limiting pathways in the photochemical reaction (viz. protonation kinetics with the ruthenium chromophore, catalyst activation via electron transfer from the QDs in the present system). Hence, this work shows how the electronic effects on light-triggered molecular catalysis are not exclusive features of the catalyst unit but depend on the whole photochemical system.     

III-V nitride epilayers for photoelectrochemical water splitting: GaPN and GaAsPN

Epilayers of single-crystal GaAsPN and GaPN semiconductor samples with varying nitrogen compositions were photoelectrochemically characterized to determine their potential to serve as water splitting photoelectrodes. The band gap and flatband potentials were determined and used to calculate the valence and conduction band edge energies. The band edges for all compositions appear to be too negative by more than 500 mV for any of the materials to effect light-driven water splitting without an external bias. Corrosion analysis was used to establish material stability under operating conditions. GaPN was found to show good stability toward photocorrosion; on the other hand, GaAsPN showed enhanced photocorrosion as compared to GaP.     

Computational modeling of green hydrogen generation from photocatalytic H2S splitting: Overview and perspectives

Hydrogen plays an important role in developing a clean and sustainable future energy scenario. Substantial efforts to produce green hydrogen from water splitting, biomass and hydrogen sulfide (H₂S) have been made in recent years. H₂S, naturally occurring or generated in fuel gas processing and industrial wastewater treatment, can be split into hydrogen and sulfur via photocatalysis. Although it is not as widely used as water splitting for green hydrogen production, this process is considered to be an appropriate and sustainable way to meet the future energy demands, adding value to H₂S. Therefore, it is essential to understand how to improve the solar light utilization and splitting efficiency of H₂S based on the existing technology and materials. Along with that effort, molecular modeling and theoretical calculations are indispensable tools to provide guidance to effectively design photocatalysts for improving hydrogen generation efficiency. In this review, we summarize the published work on H₂S photocatalysis modeling and illustrate the use of different computational methods to gain more in-depth insight into the reaction mechanisms and processes. Moreover, an overview of quantum mechanical and molecular simulation approaches combined with other modeling techniques, relevant to material science and catalysis design and applicable to H₂S splitting is also presented. Challenges and future directions for developing H₂S splitting photocatalysts are highlighted in this contribution, which is intended to inspire further simulation developments and experiments for H₂S splitting, tailoring photocatalysts design towards highly efficient hydrogen production.     

Photocatalytic Z-scheme Overall Water Splitting: Insight into Different Optimization Strategies for Powder Suspension and Particulate Sheet Systems

Achieving solar light-driven photocatalytic overall water splitting is the ideal and ultimate goal for solving energy and environment issues. Photocatalytic Z-scheme overall water splitting has undergone considerable development in recent years; specific approaches include a powder suspension Z-scheme system with a redox shuttle and a particulate sheet Z-scheme system. Of these, a particulate sheet has achieved a benchmark solar-to-hydrogen efficiency exceeding 1.1 %. Nevertheless, owing to intrinsic differences in the components, structure, operating environment, and charge transfer mechanism, there are several differences between the optimization strategies for a powder suspension and particulate sheet Z-scheme. Unlike a powder suspension Z-scheme with a redox shuttle, the particulate sheet Z-scheme system is more like a miniaturized and parallel p/n photoelectrochemical cell. In this review, we summarize the optimization strategies for a powder suspension Z-scheme with a redox shuttle and particulate sheet Z-scheme. In particular, attention has been focused on choosing appropriate redox shuttle and electron mediator, facilitating the redox shuttle cycle, avoiding redox mediator-induced side reactions, and constructing a particulate sheet. Challenges and prospects in the development of efficient Z-scheme overall water splitting are also briefly discussed.     

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。     

光催化制氢中助催化剂表面氢氧复合反应的抑制

在光催化分解水产氢的过程中,Pt等助催化剂在催化产生氢的同时也会诱导催化氢气和氧气重新复合为水的逆反应,严重降低了悬浮体系光催化全分解水产氢的效率。本文综述了近年来在逆反应抑制方面的研究进展,总结和对比分析了各种抑制逆反应策略的特点,并对这些方法的应用于悬浮体系光催化全分解水制氢的前景进行了展望。     

工业级碱性海水电解:近期进展和展望

由太阳能、风能和海洋等可再生能源驱动的工业级水分解产氢为能源和环境的可持续性发展开辟了一条极具潜力的道路。然而,在工业上最先进电解技术使用高纯水作为氢源,这将带来严重的淡水资源危机。海水分解为饮用水短缺提供了一条切实可行的解决途径,但仍面临规模工业化生产的巨大挑战。在这里,我们总结了海水分解的最新进展,包括反应机制、电极设计标准和直接海水分解的工业电解槽。深入讨论了应对海水电解中的关键挑战,如活性位点、反应选择性、耐腐蚀性和传质能力等的解决方案。此外,该文章重点总结了海水电解设备的最新发展,并提出了设计长寿命直接海水电解装置的有效策略。最后,我们对直接海水电解的未来机遇和挑战提出了自己的观点。     

Nano-architecture and material designs for water splitting photoelectrodes

This review concerns the efficient conversion of sunlight into chemical fuels through the photoelectrochemical splitting of water, which has the potential to generate sustainable hydrogen fuel. In this review, we discuss various photoelectrode materials and relative design strategies with their associated fabrication for solar water splitting. Factors affecting photoelectrochemical performance of these materials and designs are also described. The most recent progress in the research and development of new materials as well as their corresponding photoelectrodes is also summarized in this review. Finally, the research strategies and future directions for water splitting are discussed with recommendations to facilitate the further exploration of new photoelectrode materials and their associated technologies.     

Revisiting the Limiting Factors for Overall Water‐Splitting on Organic Photocatalysts

In pursuit of inexpensive and earth abundant photocatalysts for solar hydrogen production from water, conjugated polymers have shown potential to be a viable alternative to widely used inorganic counterparts. The photocatalytic performance of polymeric photocatalysts, however, is very poor in comparison to that of inorganic photocatalysts. Most of the organic photocatalysts are active in hydrogen production only when a sacrificial electron donor (SED) is added into the solution, and their high performances often rely on presence of noble metal co‐catalyst (e.g. Pt). For pursuing a carbon neutral and cost‐effective green hydrogen production, unassisted hydrogen production solely from water is one of the critical requirements to translate a mere bench‐top research interest into the real world applications. Although this is a generic problem for both inorganic and organic types of photocatalysts, organic photocatalysts are mostly investigated in the half‐reaction, and have so far shown limited success in hydrogen production from overall water‐splitting. To make progress, this article exclusively discusses critical factors that are limiting the overall water‐splitting in organic photocatalysts. Additionally, we also have extended the discussion to issues related to stability, accurate reporting of the hydrogen production as well as challenges to be resolved to reach 10 % STH (solar‐to‐hydrogen) conversion efficiency.     

光催化全分解水制氢中助催化剂表面氢氧复合反应的抑制

在光催化全分解水产氢的过程中, Pt等助催化剂在催化产生氢的同时也会诱导催化氢气和氧气重新复合为水的逆反应,严重降低了悬浮体系光催化全分解水产氢的效率.我们综述了近年来在逆反应抑制方面的研究进展,总结和对比分析了各种抑制逆反应策略的特点,并对将这些方法应用于悬浮体系光催化全分解水制氢的前景进行了展望.     

Expanded Porphyrin Nanosheet for Metal-Free Photocatalytic Water Splitting Using Visible Light

Photocatalytic water splitting to generate hydrogen gas is an ideal solution for environmental pollution and unsustainable energy issues. In the past few decades, many efforts have been made to increase the efficiency of hydrogen production. One of the most important ways is to achieve light absorption in the visible range to improve the conversion efficiency of solar energy into chemical energy, but it still presents great challenges. We here predicted a novel organic film, which can be obtained by polymerizing HTAP molecules, as an ideal material for photocatalytic water splitting. Based on first-principles calculations and Born-Oppenheimer quantum molecular dynamic simulations, the metal-free two-dimensional nanomaterial has been proven to be structurally stable, with a direct band gap of 2.12 eV, which satisfies the requirement of light absorption in the visible range. More importantly, the conduction bands and valence bands completely engulf the redox potentials of water, making the film be a promising photocatalyst for water splitting. This construction method through the topological periodicity of organic molecules provides a design scheme for the photocatalyst for water splitting.     

Photocatalytic Water Splitting: How Far Away Are We from Being Able to Industrially Produce Solar Hydrogen?

Solar water splitting (SWS) has been researched for about five decades, but despite successes there has not been a big breakthrough advancement. While the three fundamental steps, light absorption, charge carrier separation and diffusion, and charge utilization at redox sites are given a great deal of attention either separately or simultaneously, practical considerations that can help to increase efficiency are rarely discussed or put into practice. Nevertheless, it is possible to increase the generation of solar hydrogen by making a few little but important adjustments. In this review, we talk about various methods for photocatalytic water splitting that have been documented in the literature and importance of the thin film approach to move closer to the large-scale photocatalytic hydrogen production. For instance, when comparing the film form of the identical catalyst to the particulate form, it was found that the solar hydrogen production increased by up to two orders of magnitude. The major topic of this review with thin-film forms is, discussion on several methods of increased hydrogen generation under direct solar and one-sun circumstances. The advantages and disadvantages of thin film and particle technologies are extensively discussed. In the current assessment, potential approaches and scalable success factors are also covered. As demonstrated by a film-based approach, the local charge utilization at a zero applied potential is an appealing characteristic for SWS. Furthermore, we compare the PEC-WS and SWS for solar hydrogen generation and discuss how far we are from producing solar hydrogen on an industrial scale. We believe that the currently employed variety of attempts may be condensed to fewer strategies such as film-based evaluation, which will create a path to address the SWS issue and achieve sustainable solar hydrogen generation.     

表面反应在半导体光催化水分解过程中的重要性

利用光解水制氢将太阳能直接转化并储存为氢和氧的化学能是解决能源危机和环境污染的有效途径之一。光解水制氢过程中光生载流子在材料表面处发生的氧化还原反应尤为复杂,由于表面反应拥有较高的过电位以及缓慢的气体脱附速率而成为整个光解水过程中的速控步骤,因此得到了研究者的重点关注和研究。本文就催化剂表面反应过程调控的科学问题进行简要总结和展望。结合光催化水分解基本原理,(i)阐述了促进表面水分解反应速率的主要方法;(ii)介绍了表面助催化剂的作用和分类;(iii)讨论了材料表面态的钝化和保护层的包覆对表面水分解反应的影响。最后对光催化水分解表面反应研究的未来发展方向提出了若干设想。     

高压下TiSi2可见光光热催化分解水制氢的研究

系统地研究了高压下一系列TiSi2催化剂的可见光光热催化分解水制氢行为.研究结果表明,压力增加显著提高了TiSi2催化剂光催化分解水制氢速率.添加NaOH和Na2CO3有利于水分解制氢的反应进行,在一定范围内,NaOH和Na2CO3浓度增加,放氢速率增加.研究还发现,担载贵金属Pt或Ru对反应速率没有显著影响.本文还采...