利用太阳能制氢的方法及发展现状

发展清洁可再生能源是人类面临的巨大技术挑战,氢气作为一种理想的清洁能源,其制取及储运技术近年来都取得了很大进展。综述了利用太阳能分解水制氢的基本途径及发展现状,主要包括电解水制氢及人工模拟光合作用制氢、半导体光解水及其催化剂以及最有希望实现的高温热化学循环分解水制氢技术。     

光电催化分解水用可见光响应型氧化物光阳极的改性研究进展

光电催化分解水是绿色制氢的重要途径之一。由于水氧化反应在热力学和动力学上极难发生, 因而制备高效光阳极成为光电催化分解水的瓶颈问题。为满足未来商业化应用需求(太阳能制氢转换效率>10%), 研制高效光阳极成为亟待解决的关键难题。研究表明, 具有价格低廉、吸光性良好、毒性小且光电化学稳定性高等突出优点的可见光响应型氧化物: WO₃、α-Fe₂O₃和BiVO₄,是目前光电催化分解水用光阳极的理想材料。在过去几十年里, 围绕该类氧化物光阳极的研究已取得显著成果。本文重点论述了高效光电催化分解水制氢用WO₃、α-Fe₂O₃和BiVO₄光阳极改性的研究进展。另外, 文中简述了此类可见光响应型氧化物光阳极在无偏压光电催化分解水中的研究现状, 并提出其存在的问题及未来发展方向。     

High activity of hot electrons from bulk 3D graphene materials for efficient photocatalytic hydrogen production

Design and synthesis of efficient photocatalysts for hydrogen production via water splitting are of great importance from both theoretical and practical viewpoints.Many metal-based semiconductors have been explored for this purpose in recent decades.Here,for the first time,an entirely carbon-based material,bulk three-dimensionally cross-linked graphene (3DG),has been developed as a photocatalyst for hydrogen production.It exhibits a remarkable hydrogen production rate of 270 μmol·h-1·g-1cat under full-spectrum light via a hot/free electron emission mechanism.Furthermore,when combined with the widely used semiconductor TiO2 to form a TiO2/3DG composite,it appears to become a more efficient hydrogen production photocatalyst.The composite achieves a production rate of 1,205 μmol·h-1.g-1cat under ultraviolet-visible (UV-vis) light and a 7.2％ apparent quantum efficiency at 350 nm due to the strong synergetic effects between TiO2 and 3DG.     

Recent Progress in Cobalt‐Based Heterogeneous Catalysts for Electrochemical Water Splitting

Water electrolysis is considered as the most promising technology for hydrogen production. Much research has been devoted to developing efficient electrocatalysts for hydrogen production via the hydrogen evolution reaction (HER) and oxygen production via the oxygen evolution reaction (OER). The optimum electrocatalysts can drive down the energy costs needed for water splitting via lowering the overpotential. A number of cobalt (Co)‐based materials have been developed over past years as non‐noble‐metal heterogeneous electrocatalysts for HER and OER. Recent progress in this field is summarized here, especially highlighting several important bifunctional catalysts. Various approaches to improve or optimize the electrocatalysts are introduced. Finally, the current existing challenges and the future working directions for enhancing the performance of Co‐implicated electrocatalysts are proposed.     

复合相结构钙钛矿锰氧化物低场磁电阻效应

阐述了低场磁电阻及其产生的物理机制,综述了国内外近年来在复合相钙钛矿锰氧化物低场磁电阻增强这一研究领域的进展及其存在的问题.在母相中添加第二相物质形成复合相结构是低场增强磁电阻最简单和有效的方法.结合实践需要和自身研究结果提出制备复合相钙钛矿锰氧化物的新方法,即粘接法,用此方法制备出的复相材料具有很好的应用潜力.     

锰的氧化物在锂离子二次电池中的应用

锰的氧化物由于资源丰富,价格便宜、无毒无污染等特点,在锂离子二次电池正极材料的大规模生产中广具前景。简述了各种锰氧化物的制备方法,晶体结构及其与电化学性能的关系。     

Recent Advances in Conjugated Polymers for Visible-Light-Driven Water Splitting

With the ambition of solving the challenges of the shortage of fossil fuels and their associated environmental pollution, visible-light-driven splitting of water into hydrogen and oxygen using semiconductor photocatalysts has emerged as a promising technology to provide environmentally friendly energy vectors. Among the current library of developed photocatalysts, organic conjugated polymers present unique advantages of sufficient light-absorption efficiency, excellent stability, tunable electronic properties, and economic applicability. As a class of rising photocatalysts, organic conjugated polymers offer high flexibility in tuning the framework of the backbone and porosity to fulfill the requirements for photocatalytic applications. In the past decade, significant progress has been made in visible-light-driven water splitting employing organic conjugated polymers. The recent development of the structural design principles of organic conjugated polymers (including linear, crosslinked, and supramolecular self-assembled polymers) toward efficient photocatalytic hydrogen evolution, oxygen evolution, and overall water splitting is described, thus providing a comprehensive reference for the field. Finally, current challenges and perspectives are also discussed.     

Stable Rhodium (IV) Oxide for Alkaline Hydrogen Evolution Reaction

Water electrolysis in alkaline electrolyte is an attractive way toward clean hydrogen energy via the hydrogen evolution reaction (HER), whereas the sluggish water dissociation impedes the following hydrogen evolution. Noble metal oxides possess promising capability for catalyzing water dissociation and hydrogen evolution; however, they are never utilized for the HER due to the instability under the reductive potential. Here it is shown that compressive strain can stabilize RhO₂ clusters and promote their catalytic activity. To this end, a strawberry-like structure with RhO₂ clusters embedded in the surface layer of Rh nanoparticles is engineered, in which the incompatibility between the oxide cluster and the metal substrate causes intensive compressive strain. As such, RhO₂ clusters remain stable at a reduction potential up to −0.3 V versus reversible hydrogen electrode and present an alkaline HER activity superior to commercial Pt/C.     

Synergism of Geometric Construction and Electronic Regulation: 3D Se‐(NiCo)Sx/(OH)x Nanosheets for Highly Efficient Overall Water Splitting

The exploration of highly efficient electrocatalysts for both oxygen and hydrogen generation via water splitting is receiving considerable attention in recent decades. Up till now, Pt‐based catalysts still exhibit the best hydrogen evolution reaction (HER) performance and Ir/Ru‐based oxides are identified as the benchmark for oxygen evolution reaction (OER). However, the high cost and rarity of these materials extremely hinder their large‐scale applications. This paper describes the construction of the ultrathin defect‐enriched 3D Se‐(NiCo)S_x/(OH)_x nanosheets for overall water splitting through a facile Se‐induced hydrothermal treatment. Via Se‐induced fabrication, highly efficient Se‐(NiCo)S_x/(OH)_x nanosheets are successfully fabricated through morphology optimization, defect engineering, and electronic structure tailoring. The as‐prepared hybrids exhibit relatively low overpotentials of 155 and 103 mV at the current density of 10 mA cm^?2 for OER and HER, respectively. Moreover, an overall water‐splitting device delivers a current density of 10 mA cm^?2 for ≈66 h without obvious degradation.     

Anchoring ultrafine molybdenum phosphide on hierarchical three-dimensional CNTs/rGO framework as efficient electrocatalysts for hydrogen evolution

Journal of Materials Science: Materials in Electronics - Massive efforts have been made to achieve highly efficient electrocatalytic activity for hydrogen production via water splitting. Here, a...     

Self-Supported Transition-Metal-Based Electrocatalysts for Hydrogen and Oxygen Evolution

Electrochemical water splitting is a promising technology for sustainable conversion, storage, and transport of hydrogen energy. Searching for earth-abundant hydrogen/oxygen evolution reaction (HER/OER) electrocatalysts with high activity and durability to replace noble-metal-based catalysts plays paramount importance in the scalable application of water electrolysis. A freestanding electrode architecture is highly attractive as compared to the conventional coated powdery form because of enhanced kinetics and stability. Herein, recent progress in developing transition-metal-based HER/OER electrocatalytic materials is reviewed with selected examples of chalcogenides, phosphides, carbides, nitrides, alloys, phosphates, oxides, hydroxides, and oxyhydroxides. Focusing on self-supported electrodes, the latest advances in their structural design, controllable synthesis, mechanistic understanding, and strategies for performance enhancement are presented. Remaining challenges and future perspectives for the further development of self-supported electrocatalysts are also discussed.     

Nickel Diselenide Ultrathin Nanowires Decorated with Amorphous Nickel Oxide Nanoparticles for Enhanced Water Splitting Electrocatalysis

Well‐designed hybrid materials based on noble metal‐free elements have great potential to generate hydrogen (H₂) and oxygen (O₂) sustainably via overall water splitting for developing practical energy‐related technologies. Herein, an accessible method is presented to synthesize nickel diselenide (NiSe₂) ultrathin nanowires decorated with amorphous nickel oxide nanoparticles (NiO_x NPs) as multifunctional electrocatalysts (NSWANs) for hydrogen and oxygen evolution reaction (HER and OER). The NSWANs exhibit quite low HER and OER overpotentials of 174 and 295 mV, respectively, holding the current density of 20 mA cm^?2 for 24 h continuous operations in alkaline media. Meanwhile, a cell voltage of 1.547 V at the current density of 10 mA cm^?2 for overall water splitting has been achieved by the NSWANs for the practical application, which could maintain fascinating activity of 20 mA cm^?2 for 72 h without degradation. The decorated NiO_x NPs not only prevent the NiSe₂ from further oxidation but also expose requisite active sites for electrocatalytic process. It is believed that this study may provide a valuable strategy to design high‐efficiency electrocatalysts and expand the applications of selenide‐based materials.     

The oxidation behaviour of metals and alloys at high temperatures in atmospheres containing water vapour: A review

The kinetics of oxide formation in the presence of water vapour are discussed and compared with oxidation in dry atmospheres. The main protective oxide systems are considered, i.e. alumina, chromia, silica, titania and iron and nickel oxides, and with the possible exceptions of alumina and nickel oxide, oxidation rates are increased by the presence of water vapour. Scale morphology is also influenced by water vapour, and an important observation is that whisker formation is encouraged; this is believed to be due to the more rapid dissociation of water vapour compared to oxygen. In general, water vapour promotes the formation of a more porous scale. This is related to an increase in cation diffusion and consequent vacancy condensation, thereby developing a porous structure. The thermochemistry of oxide formation is discussed, and here oxide stability and hydroxide formation are considered. A significant observation is that where hydroxides or oxyhydroxides form, they generally have higher volatility than the corresponding oxide, and this leads to loss of protection.The effect of water vapour on oxide growth processes is considered. It is demonstrated that all aspects of oxide growth including adsorption, dissociation and diffusion of reactants are altered in the presence of water vapour compared with similar processes in dry conditions. The important first stages of the reaction involving adsorption and dissociation are controlled by the catalytic activity and acid base nature of oxides. For oxides formed at high temperatures very limited information is available, but, in general, data obtained at room temperature is confirmed and strongly suggests that dissociation of any gas molecule is favoured by defects in the surface. Dissociation of water seems to be more rapid at lower temperatures than, for example, oxygen, but this difference may be less pronounced at higher temperatures. Fast diffusion of water in oxides is possible due to “proton hopping”, in which protons localised at oxide ions move by transfer from one oxygen to another. Since the OH⁻ ion concentration is increased there is a resultant increase in cation vacancies, and this, in part, is responsible for the observed increase in oxidation rates. A further factor to consider is the possibility of molecular diffusion, and it has been demonstrated that where pores or voids are present in the scale, and the void contains both hydrogen and water vapour, oxidation of the surface nearest the metal will occur by reaction with water to form new oxide and the reaction product hydrogen, while a reduction reaction occurs at the surface of the void nearest the gas phase to produce water vapour. Thus it can be seen that this process provides for rapid inward diffusion of oxygen while the void gradually moves outwards from the metal/oxide interface to the oxide/gas interface.Finally, the review considers the effect of water vapour on the mechanical properties of the scale. Scale adhesion can be improved (iron oxides) or made worse (alumina and chromia) by the presence of water vapour. It is shown that while there is experimental evidence for altered mechanical behaviour, there is very little data on relevant mechanical properties. It is possible, therefore, that water vapour either alters mechanical properties of some oxides, or, as has been demonstrated, the oxide growth process has been changed. Alternatively, at least for the cases where increased oxidation rates were caused by the presence of water vapour, the observed differences between wet and dry behaviour may simply be a function of the greater scale thickness. A significant effort has been made to develop models that can be used to predict the onset scale spallation observed in industrial boilers using process steam. The further development of these models is strongly dependent upon obtaining relevant input data, and this is considered a major challenge for materials scientists.Some areas for future research are proposed.     

Bimetallic Fe-Mo sulfide/carbon nanocomposites derived from phosphomolybdic acid encapsulated MOF for efficient hydrogen generation

To tackle the energy crisis and achieve more sustainable development,hydrogen as a clean and renew-able energy resource has attracted great interest.Searching for cheap but efficient catalysts for hydrogen production from water splitting is urgently needed.In this report,bimetallic Fe-Mo sulfide/carbon nanocomposites that derived from a polyoxometalate phosphomolybdic acid encapsulated metal-organic framework MIL-100(PMA@MIL-100)have been generated and their applications in electrocatalytic hydrogen generation were explored.The PMA@MIL-100 precursor is formed via a simple one-pot hydrothermal synthesis method and the bimetallic Fe-Mo sulfide/carbon nanocomposites were obtained by chemical vapor sulfurization of PMA@MIL-100 at high temperatures.The nanocomposite samples were fully characterized by a series of techniques including X-ray diffraction,Fourier-transform infrared analysis,thermogravimetric analysis,N2 gas sorption,scanning electron microscopy,transmission elec-tron microscopy,X-ray photoelectron spectroscopy,and were further investigated as electrocatalysts for hydrogen production from water splitting.The hydrogen production activity of the best performed bimetallic Fe-Mo sulfide/carbon nanocomposite exhibits an overpotential of-0.321 V at 10 mA cm-2 and a Tafel slope of 62 mV dec-1 with a 53％reduction in overpotential compared to Mo-free counterpart composite.This dramatic improvement in catalytic performance of the Fe-Mo sulfide/carbon composite is attributed to the homogeneous distribution of the nanosized iron sulfide,MoS2 particles,and the for-mation of Fe-Mo-S phases in the S-doped porous carbon matrix.This work has demonstrated a potential approach to fabricate complex heterogeneous catalytic materials for different applications.     

Influence of oxides on the stability of zinc foam

The influence of oxides on the stabilisation of zinc foam made by foaming-compacted powder mixtures has been investigated by varying the oxide content in the zinc powder used by oxidation and reduction. Optical, scanning electron and transmission electron microscopy as well as energy dispersive X-ray mapping were used to determine the oxide distribution, morphology and structure in the foams. The study revealed that with increase in the oxide content of the foam, the maximum expansion and expansion rate increased. Small amount of nano-sized oxide particles and their cluster, which are randomly distributed, were observed within the bulk of foam. But the major fraction of oxides is observed on the surface of pores in the form of clusters. These clusters are distributed uniformly all over the surface. Effect of these oxides on the stability of foam is discussed. The formation of satellite pores, which is characteristic signature of zinc foams, and their stability, is investigated.     

Enhancing Electrocatalytic Water Splitting by Strain Engineering

Electrochemical water splitting driven by sustainable energy such as solar, wind, and tide is attracting ever‐increasing attention for sustainable production of clean hydrogen fuel from water. Leveraging these advances requires efficient and earth‐abundant electrocatalysts to accelerate the kinetically sluggish hydrogen and oxygen evolution reactions (HER and OER). A large number of advanced water‐splitting electrocatalysts have been developed through recent understanding of the electrochemical nature and engineering approaches. Specifically, strain engineering offers a novel route to promote the electrocatalytic HER/OER performances for efficient water splitting. Herein, the recent theoretical and experimental progress on applying strain to enhance heterogeneous electrocatalysts for both HER and OER are reviewed and future opportunities are discussed. A brief introduction of the fundamentals of water‐splitting reactions, and the rationalization for utilizing mechanical strain to tune an electrocatalyst is given, followed by a discussion of the recent advances on strain‐promoted HER and OER, with special emphasis given to combined theoretical and experimental approaches for determining the optimal straining effect for water electrolysis, along with experimental approaches for creating and characterizing strain in nanocatalysts, particularly emerging 2D nanomaterials. Finally, a vision for a future sustainable hydrogen fuel community based on strain‐promoted water electrolysis is proposed.     

Transition‐Metal‐Doped RuIr Bifunctional Nanocrystals for Overall Water Splitting in Acidic Environments

The establishment of electrocatalysts with bifunctionality for efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acidic environments is necessary for the development of proton exchange membrane (PEM) water electrolyzers for the production of clean hydrogen fuel. RuIr alloy is considered to be a promising electrocatalyst because of its favorable OER performance and potential for HER. Here, the design of a bifunctional electrocatalyst with greatly boosted water‐splitting performance from doping RuIr alloy nanocrystals with transition metals that modify electronic structure and binding strength of reaction intermediates is reported. Significantly, Co‐RuIr results in small overpotentials of 235 mV for OER and 14 mV for HER (@ 10 mA cm^?2 current density) in 0.1 m HClO₄ media. Therefore a cell voltage of just 1.52 V is needed for overall water splitting to produce hydrogen and oxygen. More importantly, for a series of M‐RuIr (M = Co, Ni, Fe), the catalytic activity dependence at fundamental level on the chemical/valence states is used to establish a novel composition‐activity relationship. This permits new design principles for bifunctional electrocatalysts.     

过渡金属氧化物析氧催化都是通过氧氢氧化物实现的吗?（英文）

本文首先简单回顾了电解水的发展历史以及碱性和酸性条件下电解水的电极材料特点.对于碱性条件下的电解水,电极材料以过渡金属氧化物为主.近年来,人们对于过渡金属氧化物的析氧反应开展了大量的研究,特别关注钙钛矿、尖晶石、氧氢氧化物等催化剂.析氧反应条件苛刻,一些氧化物催化剂会发生表面重构,转化为过渡金属氧氢氧化物.因此,对这些氧化物来讲,真正的催化剂表面是一个氧氢氧化物的表面.另一方面,一些氧化物在析氧反应中表现出较强的稳定性,一般认为这些氧化物的表面不会发生重构,因而没有氧氢氧化物的生成.一些已知的基于氧化物结构的活性描述参数也对该观点提供了实验和理论支持.最后,本文提出尚待回答的一个问题:在析氧反应中是否所有的过渡金属氧化物都会发生表面重构而生成一个氧氢氧化物的表面?不管以上问题的答案是什么,该如何设计预催化剂实现重构后的高活性表面将成为未来关注的热点之一.     

不同锰含量纳米MnO2-Fe2O3-CeO2/Al2O3的制备、表征及其催化还原NO/NO_2性能

减少发动机冷启动极低温度下排气中的NO_x对于生态环境与人类健康至关重要,MnO₂在低温区间对NO_x具有较高催化活性,是一种极具发展前景的纳米催化剂。通过超声波辅助共沉淀法制备不同锰含量MnO₂-Fe₂O₃-CeO₂/Al₂O₃纳米催化材料,探讨表面结构特性与其脱硝活性的内在联系。研究发现:锰含量为15%(质量分数)时具有最大比表面积与最小晶粒,活性物质分布最为均匀,金属氧化物结晶度得到抑制,Mn,Fe和Ce呈现较佳共存态,能够促进化学吸附氧的富集,并通过提高NO催化氧化成NO₂来提高快速SCR反应速率,NO₂转化率在50℃时即达到了88.5%。在改善催化材料构效关系、提高NO预氧化和快速SCR反应性能方面,优化锰含量是一种极其有效的方法。     

Designing Advanced Catalysts for Energy Conversion Based on Urea Oxidation Reaction

Urea oxidation reaction (UOR) is the underlying reaction that determines the performance of modern urea‐based energy conversion technologies. These technologies include electrocatalytic and photoelectrochemical urea splitting for hydrogen production and direct urea fuel cells as power engines. They have demonstrated great potentials as alternatives to current water splitting and hydrogen fuel cell systems with more favorable operating conditions and cost effectiveness. At the moment, UOR performance is mainly limited by the 6‐electron transfer process. In this case, various material design and synthesis strategies have recently been reported to produce highly efficient UOR catalysts. The performance of these advanced catalysts is optimized by the modification of their structural and chemical properties, including porosity development, heterostructure construction, defect engineering, surface functionalization, and electronic structure modulation. Considering the rich progress in this field, the recent advances in the design and synthesis of UOR catalysts for urea electrolysis, photoelectrochemical urea splitting, and direct urea fuel cells are reviewed here. Particular attention is paid to those design concepts, which specifically target the characteristics of urea molecules. Moreover, challenges and prospects for the future development of urea‐based energy conversion technologies and corresponding catalysts are also discussed.