金属氧化物半导体用于光热催化CO_%282%29加氢反应：最新进展和展望.pdf

物 理 化 学 学 报 Acta Phys.-Chim.Sin.2023,39(11),2212042(1 of 27)Received:December 27,2022;Revised:February 16,2023;Accepted:February 16,2023;Published online:March 2,2023.*Corresponding authors.Emails:(F.F.);(K.C.);Tel.:+86-13611576864(F.F.);+86-13222770156(K.C.).The project was supported by the National Natural Science Foundation of China(51888103),the Natural Science Foundation of Jiangsu Province,China(BK20210308),the Postdoctoral Science Foundation of China(2021M701695),the Fundamental Research Funds for the Central Universities,China(NE2019103)and the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(SJCX21_0097).国家自然科学基金(51888103)，江苏省自然科学基金(BK20210308)，中国博士后科学基金(2021M701695)，中央高校基本科研业务费专项资金(NE2019103)，江苏省研究生科研实践创新计划(SJCX21_0097)资助项目 Editorial office of Acta Physico-Chimica Sinica Review doi:10.3866/PKU.WHXB202212042 Metal Oxide Semiconductors for Photothermal Catalytic CO2 Hydrogenation Reactions:Recent Progress and Perspectives Yutong Wan,Fan Fang*,Ruixue Sun,Jie Zhang,Kun Chang*College of Materials Science and Technology,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China.Abstract:Owing to the accelerated growth of the human economy and society,the increasing concentration of CO2 in the atmosphere has caused serious ecological and environmental problems because of the greenhouse effect.In response to the challenges posed by climate change,China has made a significant commitment to“peak carbon emissions by 2030 and achieve carbon neutrality by 2060”.Ideally,converting CO2 into carbon-based energy and chemicals is supposed to be the best strategy of both worlds,mitigating the greenhouse effect while also addressing the shortage of energy supply.Among the proposed concepts for the above strategy,the scheme of reducing CO2 using renewable green H2 to produce chemicals is preferred,because it can stimulate the potential of clean energy while also reducing CO2 emission.To accelerate this reduction process,many catalytic reactions,including photocatalysis,have been designed and investigated.Owing to its high catalytic efficiency and extensive use of solar energy,photothermal catalytic CO2 hydrogenation in photocatalysis is desirable for increasing sun-to-fuel efficiency.There are two main interpretations of photothermal catalytic hydrogenation:(1)only sunlight is used as the energy source to drive the catalyst,which generates heat to promote CO2 conversion.In this case,the reaction still proceeds in the form of thermocatalysis,whereas photocatalysis has a limited effect.(2)Solar and heat energy are coupled to participate in the catalytic reaction,which has a synergistic effect.Therefore,according to the catalytic mode,the rational design and successful synthesis of photothermal catalysts are very important.Metal oxide semiconductors,owing to their unique energy band structure and chemical properties,high stability,and environmental friendliness,are widely used in the research of photothermal catalytic hydrogenation reactions.This paper reviews the research progress on metal oxide materials used in the CO2 hydrogenation reaction by photothermal catalysis.In particular,the most significant results of research in the last five years have been performed mainly from three different catalyst modulation strategies,such as supporting catalysts,applying microstructure engineering,and defect engineering.The mechanisms of these modulation strategies are summarized and presented for further understanding.In addition,this study introduces different types of photothermal hydrogenation reactors,accompanied by the effects of some key parameters on the reactions.Finally,design strategies for metal oxide catalysts are suggested,and an outlook of photothermal abatement technology is presented.Key Words:CO2 reduction;Catalytic hydrogenation;Photothermal synergy;Metal oxide;Modulation strategy 物理化学学报 Acta Phys.-Chim.Sin.2023,39(11),2212042(2 of 27)金属氧化物半导体用于光热催化金属氧化物半导体用于光热催化 CO2加氢反应：最新进展和展望加氢反应：最新进展和展望 万宇彤，方帆*，孙瑞雪，张杰，常焜*南京航空航天大学材料科学与技术学院，南京 210016 摘要：摘要：由于人类经济社会的快速发展，大气中二氧化碳的浓度逐年增加造成了严重的生态环境问题。为了应对气候变化带来的挑战，中国作出了“到2030年达到碳排放峰值，到2060年实现碳中和”的重大承诺。理想情况下，将二氧化碳转化为增值产品或太阳能燃料(如CH4、CO)是一种两全其美的策略，可以同时缓解温室效应和解决能源供需不足的问题。在为上述策略提出的设想中，利用可再生的绿H2生产化学品来减少CO2的方案是首选，它除了实现CO2减排，还可以激发清洁能源的潜力。为了研究这一还原过程，人们设计了许多催化反应，其中光催化是最理想的方案，因为太阳能是清洁和可持续的。在光催化中，光热催化二氧化碳加氢技术因其较高的催化效率和太阳能的广泛利用而成为一种很有前途的CO2转化方案。对光热催化加氢原理目前主要有两种解释：(1)仅以太阳光为能量源，驱动催化剂自身产热从而实现二氧化碳的转化。在这种情况下，反应仍以热催化方式进行。(2)光能与热能相互耦合协同催化反应的发生。因此，根据催化方式的不同，光热催化剂的合理设计和成功合成非常重要。值得关注的是，金属氧化物半导体由于其独特的能带结构和化学性质，高稳定性，环境友好等优点，被广泛应用于光热催化加氢反应的研究。在本文中，我们主要从负载催化剂、微观结构工程、缺陷工程三种不同的催化剂调控策略综述了金属氧化物材料用于光热催化CO2加氢反应的研究进展，特别是近五年的重要研究成果。同时，对这些调制策略的机理进行了总结和介绍，以供进一步理解。本文还介绍了不同类型的光热加氢反应器，以及一些重要参数对催化反应的影响。最后，对金属氧化物催化剂的设计策略提出建议，并对光热减排技术的发展提出展望。关键词：关键词：CO2还原；催化加氢；光热协同；金属氧化物；调控策略 中图分类号：中图分类号：O643 1 Introduction The continuous development of the human economy and society has contributed to the massive use of fossil fuels,resulting in the annual increase of CO2 concentration in the air 1 which has reached the alert value of 37.12 billion T shown in Fig.1.The excessive emission of CO2 has brought out an increasingly serious greenhouse effect,seriously affecting the survival of human beings and even the equilibrium of the whole ecosystem 2,3.In response to the challenges caused by climate change,China,the worlds second-largest economy and one of the signatories to the Paris Agreement,has made a significant commitment to“carbon emissions peak by 2030 and achieve carbon neutrality by 2060”.The“two-carbon”development strategy has become one of the major tasks to protect the ecological environment in China in the future.On the one hand,the development and utilization of renewable energy such as solar energy,wind energy,geothermal energy,and biomass energy 4 to reduce carbon dioxide emissions at source have shown great potential for achieving the“carbon emissions peak”target.On the other hand,for the goal of“carbon neutrality”,in addition to the CO2 capture and sequestration 5,the most striking measure is the recycling of carbon dioxide,that is,the conversion of CO2 into higher-value chemicals such as methane,methanol,and ethylene through thermal catalysis 6,electrocatalysis 7,photocatalysis 8,and other means.CO2 catalytic conversion reaction is a process in which old bonds are destroyed and new bonds are created in essence 9.From the analysis of the CO2 molecular structure,it is clear that the length of the CO bond is short,contributing to a higher energy 10.In addition,the delocalization resonance between two CO bonds aroused by the lone pair of electrons on the oxygen atom,can further strengthen the CO bond.Therefore,breaking the CO bond in CO2 is difficult,which is unfavorable to CO2 conversion both in kinetic and thermodynamic,resulting in stable chemical properties and limited conversion,requiring huge driven energy 11,12.Currently,thermocatalytic techniques can realize the CO2 hydrogenation with high activity and Fig.1 Fossil fuel and industrial carbon dioxide(CO2)emissions;Data from https:/ourworldindata.org.物理化学学报 Acta Phys.-Chim.Sin.2023,39(11),2212042(3 of 27)selectivity,having been widely applied in industrial production.By controlling the temperature and pressure of the hydrogenation reaction,it is possible to convert CO2 into a high-value-added carbonaceous compound.However,this catalytic process consumes a huge amount of thermal energy for exciting the electrons 13,14,and the energy source is always not clean.Hence,it will increase the additional energy consumption and CO2 generation,limiting the application of this technology.Photocatalytic technology used in CO2 hydrogenation has attracted much attention for its clean and sustainable utilization of the abundant solar energy in the earths atmosphere,but the light energy utilization is low because only ultraviolet(UV)or visible light can be used,extremely easy recombination of photogenerated carriers,and uncontrollable product selectivity,leading to the low-level CO2 conversion.In contrast,photothermal catalytic CO2 hydrogenation technology driven by both solar and thermal energy is an effective alternative.Photothermal catalytic CO2 hydrogenation refers to the integration of light and thermal energy in a reaction process that uses mainly sunlight as the energy source.UV and visible light serve to motivate carriers,and the photothermal effect of infrared light increasing the catalyst surface temperature,can both accelerate the reaction.As a result,the photothermal catalysis process is achieved under the irradiation of the complete solar spectrum 15,16.The introduction of light reduces the reaction activation energy barrier and overcomes the limitations of thermodynamic 17,and the existence of heat supplies energy for breaking through the activation energy barrier and kinetic bottleneck.The synergistic effect of heat and light effectively improves the productivity of CO2 conversion in the catalytic reaction 18,19.Since photothermal catalytic CO2 hydrogenation is simultaneously efficient,green,and sustainable,this novel catalytic approach is favored by more researchers.The following are the major categories for photothermal catalytic CO2 hydrogenation reactions and the details are exhibited in Table 1:(1)reverse water gas reaction(RWGS)for the synthesis of CO.This reaction is endothermic and therefore needs to be carried out at a higher temperature.Moreover,this reaction is an intermediate step in the synthesis of methanol as well as other hydrocarbons,thus having great research value.In recent years,numerous CO-selective photothermal catalysts have emerged,such as Pt-based catalyst 20,Ni-based catalyst 21,In2O3 22,etc.(2)Sabatier reaction for the synthesis of CH4.The reaction is thermodynamically favorable,but the conversion of CO2 to CH4 requires the transfer of 8 electrons and the reaction kinetics is severely limited 23.However,the reaction is expected to be applied to the synthesis of natural gas and potentially to the modulation of gas composition in the Martian atmosphere 24.The current research on photothermal catalytic CO2 hydrogenation reaction is mainly focused on the synthesis of CH4 and CO;(3)methanol synthesis by carbon dioxide hydrogenation.Due to the advantages of methanol such as convenient transport and extensive usage,methanol production by CO2 reduction is greatly significant.However,the direct conversion efficiency of CO2 to methanol through photothermal catalysis is still at a low level;(4)CO2 hydrogenation for the synthesis of C2+hydrocarbons and alcohols,etc.Due to their importance in the chemical industry,C2+products are widely used in industrial production 25.But due to the complex reaction mechanism and low product selectivity,it still has a long way to realize the efficient one-step conversion of CO2 to C2+hydrocarbons by photothermal catalysis 26.Fig.2 shows some remarkable works reported for photothermal CO2 hydrogenation.In 2014,Prof.Ye pioneered the use of group VIII metals for photothermal catalytic Table 1 The reaction free energy and heat of CO2 hydrogenation reactions.Equation Reaction G298 K/(kJmol1)H298 K/(kJmol1)1 CO2(g)+H2(g)CO(g)+H2O(g)28.6 41.2 2 CO2(g)+3H2(g)CH3OH(g)+H2O(g)3.5 49.1 3 CO2(g)+4H2(g)CH4(g)+2H2O(g)113.6 165 4 CO2(g)+xH2(g)C2Hx(g)+xH2O(g)Fig.2 Timeline of significant reported works for photothermal CO2 hydrogenation.物理化学学报 Acta Phys.-Chim.Sin.2023,39(11),2212042(4 of 27)methanation of CO2,and found that they can fully absorb visible and infrared light with a good photothermal conversion performance 27.Compared to pure photocatalytic reactions,the CO2 conversion rate of the catalyst loaded with group VIII metals is six orders of magnitude higher.This important discovery has attracted more research into this field,and since then,giving rise to enhanced advances in the photothermal catalytic CO2 hydrogenation reaction.In 2017,Prof.Ozins group compounded size-controllable Pd nanocrystals with Nb2O5 nanorods with CO yields over 18.8 molgPd1h1,CO selectivity of 99.5%,which is a milestone in the field of photothermal catalysis 28.Prof.Zhangs group obtained Al2O3-supported CoFe alloy catalysts by reducing CoFeAl LDHs nano-crystals in H2/Ar with 35%selectivity for C2+hydrocarbons 29.In 2019,some scholars prepared two-dimensional black In2O3x nanosheets,which demonstrated that the existence of oxygen vacancies substantially improved the catalytic activity of indium oxide 30.In addition,some special structures 31,MOF materials 32,etc.are used for the study of photothermal catalytic CO2 hydrogenation reaction due to their unique structural properties.The continuous development of photothermal catalytic technology in CO2 hydrogenation provides a new way to prepare high-value hydrocarbons from CO2 using abundant solar energy.In addition to the common synthesis of C1/C2 products,the Tianjin Institute of Industrial Biotechnology of the Chinese Academy of Sciences has made world-renowned achievements in the artificial synthesis of starch.They first achieved the total synthesis from CO2 to starch molecule in the laboratory without relying on photosynthesis,using CO2 and hydrogen produced by electrolysis as raw materials 33.Exciting progress has also been made in extraterrestrial artificial photosynthesis.Recently,Chinese scientists used Change-5 lunar soil(CE-5)as a catalyst to convert human respiratory waste gas(CO2 and H2O)into various high-value-added hydrocarbon fuels(CH4,CH3OH,etc.),laying the material basis for a“zero-energy”lunar life support system 34.In extraterrestrial artificial photosynthesis,CO2 and H2O are not directly reacted,but larger quantities of H2 are produced from H2O by photovoltaic electrolytic cell PV-EC(Photovoltaic-Electrocatalysis)technology.Then,high-value-added carbon fuels are generated by photothermal catalytic CO2 hydrogenation technology(Fig.3a,b),which further confirms the great significance of the research on this technology.Metal oxide materials are widely used in the research of photothermal catalytic hydrogenation reactions due to their particular band structure and chemical properties,high stability,and environmental friendliness 35.ZnO,CeO2,WO3,In2O3,and other metal oxides have been proven to be favorable catalysts for photothermal catalytic CO2 hydrogenation reactions.Among them,ZnO materials are more widely used due to their strong adsorption ability of CO2 and higher catalytic conversion ability.CeO2 materials have excellent redox capacity and oxygen storage capacity,which can provide additional oxygen release without changing their structure,and the oxygen vacancies on the surface of CeO2 can also promote catalytic reactions.However,the metal oxide materials are generally difficult to absorb most of the sunlight because of their wide band gap,the photogenerated carriers are easy to recombine and the reactive sites are limited,resulting in unsatisfactory CO2 conversion efficiency.In recent years,researchers have improved the photothermal catalytic performanc