Arificial Leaves for Solar Fuels

Large amounts of anthropogenic CO2 emissions asso-ciated with increased fossil fuel consumption have led to global warming.Upgrading CO2 and water into solar fu...     

Preface to the Special Issue of Photocatalysis for Solar Fuels

As natural photosynthesis does, direct conversion of solar energy into the storable form of chemical energy is an intriguing technology for solar energy utilization. Due to increasing concerns of energy and environmental problems caused by the consumption of fossil fuels, production of chemical solar fuels (such as hydrogen, methanol or methane, etc) by artificial photosynthesis, namely photocatalytic splitting of water or reduction of CO2, has been a hot research topic in recent years.     

Building a Bridge from Papermaking to Solar Fuels

Black liquor, an industrial waste product of papermaking, is primarily used as a low‐grade combustible energy source. Despite its high lignin content, the potential utility of black liquor as a feedstock in products manufacturing, remains to be exploited. Demonstrated here in is the use of black liquor as a primary feed‐stock for synthesizing graphene quantum dots that exhibit both up‐conversion and photoluminescence when excited using visible/near‐infrared radiation, thereby enabling the photosensitization of ultraviolet‐absorbing TiO₂ nanosheets. In addition, these graphene quantum dots can trap photo‐generated electrons to realize the effective separation of electron‐hole pairs. Together, these two processes facilitate the solar‐powered generation of H₂ from H₂O, and CO from H₂O–CO₂, using broadband solar radiation.     

Solar Electricity and Solar Fuels: Status and Perspectives in the Context of the Energy Transition

The energy transition from fossil fuels to renewables is already ongoing, but it will be a long and difficult process because the energy system is a gigantic and complex machine. Key renewable energy production data show the remarkable growth of solar electricity technologies and indicate that crystalline silicon photovoltaics (PV) and wind turbines are the workhorses of the first wave of renewable energy deployment on the TW scale around the globe. The other PV alternatives (e.g., copper/indium/gallium/selenide (CIGS) or CdTe), along with other less mature options, are critically analyzed. As far as fuels are concerned, the situation is significantly more complex because making chemicals with sunshine is far more complicated than generating electric current. The prime solar artificial fuel is molecular hydrogen, which is characterized by an excellent combination of chemical and physical properties. The routes to make it from solar energy (photoelectrochemical cells (PEC), dye‐sensitized photoelectrochemical cells (DSPEC), PV electrolyzers) and then synthetic liquid fuels are presented, with discussion on economic aspects. The interconversion between electricity and hydrogen, two energy carriers directly produced by sunlight, will be a key tool to distribute renewable energies with the highest flexibility. The discussion takes into account two concepts that are often overlooked: the energy return on investment (EROI) and the limited availability of natural resources—particularly minerals—which are needed to manufacture energy converters and storage devices on a multi‐TW scale.     

太阳能光催化制氢研究进展

随着人类社会的快速发展和传统能源的急剧消耗,能源紧缺和环境污染已经成为制约人类社会可持续发展的重要因素,构建清洁的环境友好的可再生新能源体系是当前各国高度关注的焦点和重大战略.在众多绿色环保、可持续新能源选项中,半导体光催化制氢因其可利用清洁可再生的太阳能制取高效清洁氢能,有望完全解决能源紧缺和环境污染问题,成为最有应用前景的技术之一. 本文通过概述半导体光催化制氢原理、半导体光电化学及光电稳定性、半导体光催化制氢效率,重点介绍半导体光催化剂、光生电荷分离及光催化制氢体系等方面若干新进展,并对太阳能光催化制氢技术的发展加以评述和展望.     

Ionic Liquid Propellants: Future Fuels for Space Propulsion

Use of green propellants is a trend for future space propulsion. Hypergolic ionic liquid propellants, which are environmentally‐benign while exhibiting energetic performances comparable to hydrazine, have shown great potential to meet the requirements of developing nontoxic high‐performance propellant formulations for space propulsion applications. This Concept article presents a review of recent advances in the field of ionic liquid propellants.     

Conversion of Solar Energy to Fuels by Inorganic Heterogeneous Systems

Over the last several years,the need to find clean and renewable energy sources has increased rapidly because current fossil fuels will not only eventually be depleted,but their continuous combustion leads to a dramatic increase in the carbon dioxide amount in atmosphere.Utilisation of the Sun’s radiation can provide a solution to both problems.Hydrogen fuel can be generated by using solar energy to split water,and liquid fuels can be produced via direct CO2 photoreduction.This would create an essentially free carbon or at least carbon neutral energy cycle.In this tutorial review,the current progress in fuels’ generation directly driven by solar energy is summarised.Fundamental mechanisms are discussed with suggestions for future research.     

光催化CO_2转化为碳氢燃料体系的综述

传统化石能源燃烧产生CO2引起的地球变暖和能源短缺已经成为一个严重的全球性问题.利用太阳光和光催化材料将CO2还原为碳氢燃料,不仅可以减少空气中CO2浓度,降低温室效应的影响,还可以提供碳氢燃料,缓解能源短缺问题,因此日益受到各国科学家的高度关注.本文综述了光催化还原CO2为碳氢燃料的研究进展,介绍了光催化还原CO2的反应机理,并对现阶段报道的光催化还原CO2材料体系进行了整理和分类,包括TiO2光催化材料,ABO3型钙钛矿光催化材料,尖晶石型光催化材料,掺杂型光催化材料,复合光催化材料,V、W、Ge、Ga基光催化材料及石墨烯基光催化材料.评述了各种材料体系的特点及光催化性能的一些影响因素.最后对光催化还原CO2的研究前景进行了展望.     

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。     

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.     

Photocatalytic Conversion of Waste Plastics into C2 Fuels under Simulated Natural Environment Conditions

Reported here is the first highly selective conversion of various waste plastics into C₂ fuels under simulated natural environment conditions by a sequential photoinduced C?C cleavage and coupling pathway, where single‐use bags, disposable food containers, food wrap films, and their main components of polyethylene, polypropylene, and polyvinyl chloride can be photocatalytically transformed into CH₃COOH without using sacrificial agents. As an example, polyethylene is photodegraded 100 % into CO₂ within 40 h by single‐unit‐cell thick Nb₂O₅ layers, while the produced CO₂ is further photoreduced to CH₃COOH. Various methods and experiments disclose that O₂ and ^.OH radicals trigger the oxidative C?C cleavage of polyethylene to form CO₂, while other investigations show that the yielded CH₃COOH stems from CO₂ photoreduction by C?C coupling of ^.COOH intermediates. This two‐step plastic‐to‐fuel conversion may help to simultaneously address the white pollution crisis and harvest highly valuable multicarbon fuels in natural environments.     

全无机钙钛矿太阳电池: 现状与未来

近年来,基于ABX₃结构的有机无机杂化钙钛矿材料因其具有优良的光电特性和廉价的制作成本得到了全世界的广泛关注,但体系中的有机组分容易受到光、热、湿等外界条件的影响而分解,导致器件的PCE发生严重的下降,极大地限制了PSCs(Perovskite solar cells, PSCs)的产业化进程。利用纯无机阳离子完全取代ABX₃结构中的A位有机阳离子制备出全无机钙钛矿材料,因其优异的热稳定性和环境稳定性而得到了快速的发展。现阶段,基于全无机钙钛矿材料的全无机钙钛矿太阳能电池(I-PSCs)的效率已超过19%,应用前景广阔。本文回顾了近年来全无机钙钛矿材料的研究进展,对不同类型的全无机钙钛矿材料进行了综述和讨论,从成膜工艺、掺杂工程、后处理工程等方面论述了如何提升器件的稳定性。最后,对I-PSCs的大面积制备及其柔性应用进行了介绍,揭示了I-PSCs面临的挑战,并对该领域进行了展望。     

光催化CO2转化为碳氢燃料体系的综述

传统化石能源燃烧产生CO₂引起的地球变暖和能源短缺已经成为一个严重的全球性问题. 利用太阳光和光催化材料将CO₂还原为碳氢燃料, 不仅可以减少空气中CO₂浓度, 降低温室效应的影响, 还可以提供碳氢燃料, 缓解能源短缺问题, 因此日益受到各国科学家的高度关注. 本文综述了光催化还原CO₂为碳氢燃料的研究进展, 介绍了光催化还原CO₂的反应机理, 并对现阶段报道的光催化还原CO₂材料体系进行了整理和分类, 包括TiO₂光催化材料, ABO₃型钙钛矿光催化材料, 尖晶石型光催化材料, 掺杂型光催化材料, 复合光催化材料, V、W、Ge、Ga基光催化材料及石墨烯基光催化材料. 评述了各种材料体系的特点及光催化性能的一些影响因素. 最后对光催化还原CO₂的研究前景进行了展望.     

Tetrazole Linkages as Photoactivated Fuels for Light-Regulated Photothermal/Photocatalytic Propulsion of Versatile Polymer Nanoplatforms

Colloidal motors with multimode propulsion have attracted considerable attention because of enhanced transportability. It is a great challenge to fabricate colloidal motors powered by a single engine for multimode synergistic propulsion. Herein, we report on Janus versatile polymer nanoplatforms integrating various functionalities via tetrazole linkages for light-regulated multimode synergistic propulsion in the liquid. The presence of tetrazole linkages in the polymers endows the nanoparticles with various photoresponsive capabilities. A sole energy source (ultraviolet or visible light) simultaneously activates photocatalytic N₂ release and photothermal conversion within the tetrazole-containing polymer phase at one side of asymmetric nanoparticles for converting light energy into photothermal/photocatalytic propulsion independent of the surrounding chemical medium. The photoactivated locomotion using tetrazoles as light-triggered fuels highly corresponds to light wavelengths, light powers and tetrazole contents. The tetrazole linkages capable of incorporating various functionalities to the polymer nanoparticles allow on-demand customizing of the colloidal motors, showing great potential in bio-applications.     

Spatiotemporal Utilization of Latent Heat in Erythritol-based Phase Change Materials as Solar Thermal Fuels

Solar thermal fuels (STFs) have been particularly concerned as sustainable future energy due to their impressive ability to store solar energy in chemical bonds and controllably release thermal energy. However, currently studied STFs mainly focus on molecule-based materials with high photochemical activity, toxicity, and compromised features, which greatly restricts their applications in practical scenarios of solar energy utilization. Herein, we present a novel erythritol-based composite phase change material (PCM) as a new type of STFs with an outstanding capability to store solar energy as latent heat in its stable supercooling state and release thermal energy as needed. This composite PCM with stored thermal energy can be maintained stably at room temperature and subsequently release latent heat as high as 224.9 J/g during the crystallization process triggered by thermal stimuli. Remarkably, solar energy can be converted into latent heat stored in the composite PCM over months. Through mechanical stimulations, the released latent heat can increase the temperature of the composite up to 91 °C. This work presents a new concept of using spatiotemporal storage and release of latent heat in PCMs for solar energy utilization, making it a potential candidate as STFs for developing future clean energy techniques.     

Solar Fuels: Visible-Light-Driven Generation of Dihydrogen at p-Type Silicon Electrocatalysed by Molybdenum Hydrides

We show that a robust molybdenum hydride system can sustain photoelectrocatalysis of a hydrogen evolution reaction at boron-doped, hydrogen-terminated, p-type silicon. The photovoltage for the system is about 600-650?mV and the current densities, which can be sustained at the photocathode in non-catalytic and catalytic regimes, are similar to those at a photoinert vitreous carbon electrode. The kinetics of electrocatalysed hydrogen evolution at the photocathode are also very similar to those measured at vitreous carbon-evidently visible light does not significantly perturb the catalytic mechanism. Importantly, we show that the doped (1-10?Ω?cm) p-type Si can function perfectly well in the dark as an ohmic conductor and this has allowed direct comparison of the cyclic voltammetric behaviour of the response of the system under dark and illuminated conditions at the same electrode. The p-type Si we have employed optimally harvests light energy in the 600-700?nm region and with 37?mW?cm(-2) illumination in this range; the light to electrochemical energy conversion is estimated to be 2.8?%. The current yield of hydrogen under broad tungsten halide lamp illumination at 90?mW?cm(-2) is (91±5)?% with a corresponding chemical yield of (98±5)?%.     

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.