太阳能光催化制氢研究进展*

由于化石燃料本身的不可持续性,以及燃烧化石燃料释放的大量CO₂ 产生的温室效应、环境污染等严重的全球性问题,构建洁净的、环境友好的、非化石燃料的、可再生新能源体系,已经成为世界各国高度关注的焦点和重大战略。太阳能由于其取之不竭、洁净无污染、可再生等优点,必将在未来的新能源开发中占据举足轻重的地位。而氢能具有高燃烧值、燃烧产物是水因此无环境污染等优点,因此,利用自然界丰富的太阳能光催化制氢作为可持续发展的新能源途径之一,正日益受到国际社会的高度关注。本文简要综述了近年来这一研究领域的一些重要进展,总结了本课题组在半导体光催化制氢研究方面所取得的最新结果,并对太阳能光催化制氢的未来发展进行展望。     

太阳能光催化分解水制氢※

利用太阳能光催化分解水制氢是解决能源环境问题并实现太阳能有效转化和储存最有前途的技术之一, 这一“圣杯”式反应经过几十年不懈努力取得了诸多重要研究进展. 本文将综述光催化分解水制氢体系的基本概念、活性测试方法与注意事项、光催化材料种类等; 并从光催化分解水制氢的光吸收、光生电荷分离和表面催化反应等基本过程和关键科学问题的角度总结其重要研究进展, 最后对于太阳能光催化分解水制氢的挑战和潜在的发展方向进行分析和展望. 希望通过本综述的简要介绍能让刚从事光催化分解水制氢研究的青年科技人员清晰地了解掌握该领域的一些基本概念、操作规范、研究总体进展和现状等.     

d10和d0电子构型半导体光催化制氢研究进展

光催化分解水制氢是获得廉价氢源的最理想途径,光催化剂的研究是此项技术实施的关键。本文从光催化制氢的机理、光催化剂的种类,以及具有d0和d10电子构型的光催化剂的制氢性能三个方面,对目前光催化分解水制氢领域的研究进展进行了总结,提出了光催化分解水制氢存在的问题、所面临的挑战以及该领域未来发展的方向。     

光催化分解水制氢研究进展

光催化分解水制氢,其学术和社会意义无疑是极其广泛而深远的.这一点至少早在科幻之父儒勒·凡尔纳(JulesVerne)生活的时代就被人们所认知,下面引用JulesVerne在1874年出版的《神秘岛》中的一段表述,让我们来再次重温这一课题的伟大意义.J.Verne写到:“Waterdecomposedintoitsprimitiveelements,anddecomposeddoubtlessbyelectricity,whichwillthenhavebecomeapowerfulandmanageableforce……Yes,myfriends,Ibelievethatwaterwillsomedaybeemployedasfuel,thathydrogenandoxygen,whichconstituteit,usedsinglyortogether,willfurnish…     

半导体光催化

用半导体粒子作光催化剂早已有报道,但在Fujishima用半导体作光电极分解水及Bard将光电化学理论扩展到半导体微粒光催化剂的报道发表之后,半导体光催化才有很大的发展。从太阳能利用的观点来看,半导体光催化有着重大的应用前景。     

光催化制氢研究进展

The photocatalytic hydrogen evolution reaction (PHER) has gained much attention as a promising strategy for the generation of clean energy. As opposed to conventional hydrogen evolution strategies (steam methane reforming, electrocatalytic hydrogen evolution, etc.), the PHER is an environmentally friendly and sustainable method for converting solar energy into H₂ energy. However, the PHER remains unsuitable for industrial applications because of efficiency losses in three critical steps: light absorption, carrier separation, and surface reaction. In the past four decades, the processes responsible for these efficiency losses have been extensively studied. First, light absorption is the principal factor deciding the performance of most photocatalysts, and it is closely related to band-gap structure of photocatalysts. However, most of the existing photocatalysts have a wide bandgap, indicating a narrow light absorption range, which restricts the photocatalytic efficiency. Therefore, searching for novel semiconductors with a narrow bandgap and broadening the light absorption range of known photocatalysts is an important research direction. Second, only the photogenerated electrons and holes that migrate to the photocatalyst surface can participate in the reaction with H₂O, whereas most of the photogenerated electrons and holes readily recombine with one another in the bulk phase of the photocatalysts. Hence, tremendous effort has been undertaken to shorten the charge transfer distance and enhance the electric conductivity of photocatalysts for improving the separation and transfer efficiency of photogenerated carriers. Third, the surface redox reaction is also an important process. Because water oxidation is a four-electron process, sluggish O₂ evolution is the bottleneck in photocatalytic water splitting. The unreacted holes can easily recombine with electrons. Sacrificial agents are widely used in most catalytic systems to suppress charge carrier recombination by scavenging the photogenerated holes. Moreover, the low H₂ evolution efficiency of most photocatalysts has encouraged researchers to introduce highly active sites on the photocatalyst surface. Based on the abovementioned three steps, multifarious strategies have been applied to modulate the physicochemical properties of semiconductor photocatalysts with the aim of improving the light absorption efficiency, suppressing carrier recombination, and accelerating the kinetics of surface reactions. The strategies include defect generation, localized surface plasmon resonance (LSPR), element doping, heterojunction fabrication, and cocatalyst loading. An in-depth study of these strategies provides guidance for the design of efficient photocatalysts. In this review, we focus on the mechanism and application of these strategies for optimizing light absorption, carrier separation and transport, and surface reactions. Furthermore, we provide a critical view on the promising trends toward the construction of advanced catalysts for H₂ evolution.     

光催化完全分解水制氢研究进展

由完全分解水的特殊性出发,从材料的结构和能带设计以及材料的表面修饰等方面对完全分解水光催化剂的研制及其分解水产氢产氧性能进行了评述.介绍了Z型体系在完全分解水制氢方面的原理,以及目前已经开发出来的几个Z型体系.对光催化完全分解水研究中存在的问题进行了简单分析.     

TiO2光催化分解水制氢研究进展

综述了近几年改善TiO2光催化分解水制氢的方法措施.向水中添加供电子物质可减少光生电子与空穴的复合,添加碳酸盐或碘化物有利于光生电子与空穴分离;TiO2表面沉积适量的金属颗粒也有利于实现电子和空穴分离,但沉积太多的金属颗粒不但降低TiO2对光的吸收而且还可能成为光生电荷复合的中心;掺杂合适的金属离子通过形成杂质能级可把TiO2的吸光范围至拓宽可见光,掺杂非金属元素使TiO2的带隙(Eg)变窄,从而使TiO2的吸光红移更明显,但掺杂离子有可能成为光生电荷复合的中心;染料敏化或半导体复合有利于实现电荷分离,提高光电转换效率.将多种修饰方法有机结合起来制取氢足目前的一个研究方向,最后分析了未来的研究重点.     

太阳能分解水制氢最近进展:光催化、光电催化及光伏-光电耦合途径

能源是人类生存和发展的物质基础,太阳能作为最丰富的清洁可再生能源之一,其开发利用受到了世界范围内的广泛关注.通过光催化分解水制氢将太阳能以化学能的形式储存起来不仅能利用太阳能制取高燃烧值的氢能,同时氢能可与CO2综合利用结合起来,在减少碳排放的同时,生成高附加值的化学品,实现碳氢资源的优化利用.光催化分解水制氢在过去的几年里取得了长足的进步,本综述从三种研究广泛的太阳能光催化分解水制氢途径(即光催化、光电催化以及光伏-光电耦合途径)入手,分别简要介绍了太阳能分解水制氢在近几年取得的最新研究进展.利用纳米粒子悬浮体系进行光催化分解水制氢成本低廉、易于规模化放大,被认为是未来应用最可行的方式之一,但是太阳能转化利用效率还偏低.最新报道的SrTiO3:La,Rh/Au/BiVO4:Mo光催化剂其太阳能到氢能(STH)转化效率已超过了1.0%,相比之前报道的大多数光催化剂体系有了数量级的飞跃,让人们对太阳能光催化分解水制氢未来的规模化应用看到了希望.高效宽光谱响应的光催化剂、高效电荷分离策略、新型高效助催化剂以及气体分离新方法和新材料等,均是粉末光催化剂体系研究最为关键的问题;光电催化分解水在过去2–3年内发展迅速,在一些典型的光阳极半导体材料(如BiVO4和Ta3N5等)体系上太阳能利用效率超过2.0%以上.最新研究发现,在Ta3N5光阳极的研究中,通过在光电极表面合理设计和构筑空穴传输层和电子阻挡层等策略,光电流和电极稳定性均可得到大幅度提升,光电流大小甚至可接近Ta3N5材料的理论极限电流.如果能进一步在过电位和电极稳定性上取得突破,该体系的STH转化效率还会得到大幅度改进.此外,光阴极的研究也越来越受到了研究者的关注;光伏-光电耦合体系在三种途径里面太阳能制氢效率最高,在多个体系上已超过10%以上,最近报道的利用多结GaInP/GaAs/Ge电池与Ni电催化剂耦合,其太阳能制氢效率可达到22.4%.虽然该种制氢途径的效率已超过其工业化应用的要求,但是光伏电池的成本(尤其是多结GaAs太阳电池)极大限制了其大面积规模化应用,同时还要考虑电催化剂的成本和效率等,光伏-光电耦合制氢是成本最高的太阳能制氢途径.需要指出的是,光伏-光电耦合制氢有望在一些特殊的领域最先取得实际应用,如为外太空航天器、远洋航海以及孤立海岛等传统能源无法满足的地方提供能源供给.总之,太阳能分解水制氢研究取得了一系列重要进展,太阳能制氢效率得到了大幅度提升,也是目前世界范围内关注的研究热点之一,不仅具有强的潜在工业应用背景,更为基础科学提供了诸多新的研究课题.这一极具挑战的研究领域,在先进技术快速发展和基础科学问题认识不断提高的基础上,不久的将来,有望在不久的将来在基础科学和应用研究方面取得重大突破.     

太阳能光解水制氢的研究进展

本文概述了利用光催化技术催化分解水制氢的反应机理和研究进展。结合作者的最近研究,重点描述了TiO2及过渡金属氧化物,层状金属氧化物以及某些能利用可见光的光催化材料的结构和光催化特性,阐述了核课题的意义和今后的研究方向。     

双碳目标下太阳能制氢技术的研究进展

“双碳目标”的实现需要精准的政策引导和开发可替代的清洁能源. 近年来, 氢能由于具有来源丰富、热值高、清洁低碳、应用场景多样等特点, 受到了学者们越来越多的关注. 在传统制氢技术中, 化石燃料制氢技术应用最为广泛, 但其制氢反应过程造成的能耗和温室气体释放量较大. 而光催化分解水制氢技术是将太阳能转换为氢能, 将太阳能以化学能的形式储存起来, 这样不仅能利用太阳能制取氢气, 而且可以将氢能与CO₂结合起来生产高附加值的化学品, 在减少碳排放的同时, 实现碳氢资源的综合利用. 综述了可实现太阳能制氢的光催化制氢(PC)、光电催化制氢(PEC)和光伏电催化耦合制氢(PV-EC)技术的研究进展, 阐释了相关技术的基本原理, 介绍了制氢技术中的关键材料, 对三种制氢技术发展过程中太阳能制氢(STH)转化效率、材料稳定性的相关研究进行了详细总结. 最后对三种太阳能制氢技术面临的关键挑战和未来发展方向进行了探讨和展望.     

Harvesting Solar Light with Crystalline Carbon Nitrides for Efficient Photocatalytic Hydrogen Evolution

Described herein is the photocatalytic hydrogen evolution using crystalline carbon nitrides (CNs) obtained by supramolecular aggregation followed by ionic melt polycondensation (IMP) using melamine and 2,4,6‐triaminopyrimidine as a dopant. The solid state NMR spectrum of ¹⁵N‐enriched CN confirms the triazine as a building unit. Controlling the amount and arrangements of dopants in the CN structure can dramatically enhance the photocatalytic performance for H₂ evolution. The polytriazine imide (PTI) exhibits the apparent quantum efficiency (AQE) of 15 % at 400 nm. This method successfully enables a substantial amount of visible light to be harvested for H₂ evolution, and provides a promising route for the rational design of a variety of highly active crystalline CN photocatalysts.     

染料敏化可见光催化制氢研究进展

染料敏化是拓展宽禁带光催化剂激发波长范围、有效利用太阳光中可见光部分的重要手段. 本文介绍了染料敏化分解水制氢的基本原理, 综述了染料敏化剂、基质或载体、染料与基质的相互作用、产氢助催化剂以及电子牺牲剂的研究进展. 并对光敏化体系中电荷转移途径及稳定性问题进行了讨论.     

MoS2 as a Co-Catalyst for Photocatalytic Hydrogen Production: A Mini Review

Molybdenum disulfide (MoS₂), with a two-dimensional (2D) structure, has attracted huge research interest due to its unique electrical, optical, and physicochemical properties. MoS₂ has been used as a co-catalyst for the synthesis of novel heterojunction composites with enhanced photocatalytic hydrogen production under solar light irradiation. In this review, we briefly highlight the atomic-scale structure of MoS₂ nanosheets. The top-down and bottom-up synthetic methods of MoS₂ nanosheets are described. Additionally, we discuss the formation of MoS₂ heterostructures with titanium dioxide (TiO₂), graphitic carbon nitride (g-C₃N₄), and other semiconductors and co-catalysts for enhanced photocatalytic hydrogen generation. This review addresses the challenges and future perspectives for enhancing solar hydrogen production performance in heterojunction materials using MoS₂ as a co-catalyst.     

Production of Hydrogen Peroxide by Photocatalytic Processes

Hydrogen peroxide (H₂O₂) has received increasing attention because it is not only a mild and environmentally friendly oxidant for organic synthesis and environmental remediation but also a promising new liquid fuel. The production of H₂O₂ by photocatalysis is a sustainable process, since it uses water and oxygen as the source materials and solar light as the energy. Encouraging processes have been developed in the last decade for the photocatalytic production of H₂O₂. In this Review we summarize research progress in the development of processes for the photocatalytic production of H₂O₂. After a brief introduction emphasizing the superiorities of the photocatalytic generation of H₂O₂, the basic principles of establishing an efficient photocatalytic system for generating H₂O₂ are discussed, highlighting the advanced photocatalysts used. This Review is concluded by a brief summary and outlook for future advances in this emerging research field.     

Recent Advances in the Use of Black TiO2 for Production of Hydrogen and Other Solar Fuels

Black TiO₂ has emerged as one of the most promising photocatalysts recently discovered. The reason behind its catalytic activity is considered to be due to the presence of defects and Ti³⁺ species at the surface of black TiO₂ nanostructures, which are crucial for its diverse applications. Moreover, disordered/crystalline surface layers and bulk regions have been identified and appear to influence the intrinsic properties of the material. Here, we present the latest studies on the use of black TiO₂ for metal free hydrogen production, as well as for CO₂ photoreduction and N₂ photofixation. After highlighting the structure/property relations, we conclude with some critical questions and suggest further topics of research in order to better understand the underlying mechanisms of light absorption in black TiO₂, especially towards solar fuels production.