光伏与光电催化相结合的CO2还原制备高附加值化学品及相关机理研究

With the development of social economy, fossil fuel has been unable to meet the human demand for energy. Moreover, fossil fuel combustion emits large amount of greenhouse gas CO2. CO2 reduction via photoelectrocatalysis combined with photovoltaics has the merits of both high conversion efficiency of electrocatalysis and environment-friendliness and low energy consumption of photocatalysis. This project will perform the photoelectrocatalytic reduction of CO2 using dye-sensitized solar cells as driving force, achieving total solar-driven catalytic conversion of CO2 into useful fuels and value-added chemical materials without external electrical input. Firstly, a series of transition metal-based molecule catalysts, nano semiconductor thin films, and molecule catalyst/semiconductor composite electrodes with different photoelectrochemical properties will be designed and synthesized. Afterwards, the output photovoltage/photocurrent of the solar cells will be regulated via changing the structure of the dyes or fabricating multi junction series/parallel solar cells. Finally and the most important, the combination of photovoltaics with photoelectrocatalytic reduction of CO2, the influence mechanism of the photovoltage/photocurrent of the solar cells on the CO2 reduction pathways and conversion efficiency, as well as the influence of the molecule catalyst and the bonding mode of the molecule catalysts with the semiconductor films on CO2 reduction pathways and conversion efficiency will be systematically investigated by various off line and in-situ characterization techniques, such as UV-vis, cyclic voltammetry, photoelectrochemical measurements, in-situ FT-IR, in-situ ESR, laser flash photolysis, GC, 13C and 18O isotope labeling, and GC-MS, etc.. This research can help to provide experimental basis and theoretical guidance for synthesizing efficient transition metal-based molecule catalysts and semiconductor nano catalysts, better understanding the reduction pathway, designing applicable device for CO2 photo/electrochemical reduction, and further increasing the conversion efficiency of CO2 reduction.

随着社会经济的发展，化石能源已无法满足人类的能源需求，且燃烧排放出大量温室气体CO2。光伏发电与光电催化相结合进行CO2还原具有电催化的高转换效率和光催化的绿色清洁耗能低的优势。本项目拟将染料敏化太阳电池与光电催化还原CO2有机结合，实现全太阳能驱动的CO2转化为高附加值化学品。首先设计合成具有不同光电化学性质的过渡金属基分子催化剂和半导体复合的光电极；然后通过改变光敏染料结构或组建多结串/并联电池组调控电池的光电压/电流；最后借助各种离线和原位表征技术，系统研究光伏电池与光电催化还原CO2的有机结合及电池电压/电流对CO2催化还原的反应路径和转化效率的影响机制，并研究分子催化剂修饰半导体薄膜及二者的键合方式对还原性能的影响，从而为合成CO2光/电催化还原用高效分子催化剂，纳米半导体催化剂，更好地理解CO2还原的反应路径，研发合适的反应装置，进一步提高CO2还原转化效率提供实验和理论依据。

随着社会经济的发展，化石能源已无法满足人类的能源需求，且燃烧排放出大量温室气体CO2。太阳能驱动的CO2催化还原具有绿色清洁耗能低的优势。本项目主要研究太阳能驱动的CO2转化为高附加值化学品，揭示CO2还原相关机理和性能影响机制，并研究分子催化剂修饰半导体及二者复合方式对催化性能的影响。项目执行过程中证明了可将光伏电池与催化还原CO2有机结合实现全太阳能驱动的CO2还原转化；阐明了纳米晶氧化物衍生制备的Cu电极表面Cu2O的存在是CO2还原成C2产物的关键活性位点；揭示了氮化碳/羧基铁卟啉（g-C3N4/FeTCPP）复合催化剂催化还原CO2的性能及相关电子转移机理；中红外飞秒瞬态吸收证明碳点掺杂可使g-C3N4上自由或表面浅束缚态的电子寿命降低，碳点可以作为g-C3N4电子转移的通道促进光生电子从g-C3N4向催化中心铁卟啉转移，进而提高复合体系催化还原CO2的性能；针对CdS/铁卟啉复合体系，分别通过引入锌掺杂合成硫锌镉固溶体、硫化镉表面乙二胺修饰、原位合成CdS/Bi2S3异质结和CdS/Bi2S3/FeTCPP Z-Scheme型催化体系等构建了复合界面电荷传输通道提高界面电荷转移效率，提高载流子利用效率，实现了电子-空穴在空间上的有效分离，提高了电荷的利用效率，最终实现了对CO2的高效和高选择性催化还原；最后，以Au NP/金红石TiO2为模型，研究了贵金属纳米粒子改善反应动力学，并从动力学角度解释了催化反应中的活性和选择性问题。项目执行过程中已发表SCI收录论文10篇，影响因子均大于3，其中3篇Appl. Catal. B: Environ.的影响因子大于15，另外还有三篇未发表的相关工作和两篇专利正在投稿中。项目的开展为合成高效CO2催化还原用催化剂，更好地理解CO2还原的反应路径和相关还原机理，进一步提高CO2还原转化效率提供了实验依据和理论指导。