g-C3N4/WOx异质结能带结构的调控及光催化还原CO2产物选择性研究

利用太阳能将CO2还原为甲烷、甲醇等有机物，不仅可以实现碳资源的循环利用，还可以降低大气中CO2含量。催化剂对于CO2还原起着至关重要作用，因此合成光催化效率高、选择性好的催化剂对于碳的再利用具有重要意义。本项目利用g-C3N4和WOx能带结构特点构建g-C3N4/WOx 复合催化剂，研究水蒸气条件下CO2还原的催化活性和选择性。通过形貌控制、金属/非金属掺杂或表面改性调节g-C3N4和WOx的带隙和导带/价带电势，进而调控g-C3N4/WOx能带结构；通过WOx表面缺陷的形成、氧空位浓度的调节及表面羟基化处理，调控反应气体在催化剂表面的吸附，并协同催化条件的优化及催化剂导带电子密度的控制，实现催化剂的催化选择性。研究g-C3N4/WOx异质结能带结构和表面性质与CO2还原产物选择性之间的关系，阐明影响催化选择性的热力学和动力学因素, 为设计、构筑新型CO2还原催化剂提供借鉴。

Utilizing the abundant solar energy to convert CO2 into fuels such as methane or methanol could not only achieve the recycle of carbon resources but also reduce the atmospheric levels of carbon dioxide. Photocatalysts play a vital role in the conversion process and hence, developing efficient visible-light-driven photocatalysts with high efficiency and good selectivity has been an active field of intensive research. In this project, a series of g-C3N4/WOx composites will be constructed by utilizing the band characteristic of g-C3N4 and WOx based on designing of Z-scheme photocatalysts for CO2 photoreduction, and their photocatalytic performance and reduction selectivity will be investigated in the presence of water vapor under visible-light irradiation. To satisfy the demand of the catalytic selectivity of the photocatalysts to the potential of the conduction band, the band energy structures for the g-C3N4/WOx heterojunctions are modulated by tuning the band gap and the potential of the conduction/valence band of g-C3N4 and WOx respectively, via morphology controlling, metal/non-metal doping or surface modifying. The photocatalytic selectivity of CO2 reduction is achieved by controlling the adsorption of the reactant on the surface of the catalysts via the formation of the surface defect of WOx, the adjustment of the oxygen vacancy concentration, and/or the treatment of the surface hydroxylation, accompanying with the optimization of experimental condition and the control of the photogenerated electron density on the conduction band of the photocatalysts. The relationship between the band energy structure of the g-C3N4/WOx heterojunctions and the catalytic selectivity of CO2 photoreduction will be studied, and the influence of thermodynamical and dynamical factors on the selectivity will also be explored. Results of this project may provide some insights into the design of new photocatalysts for CO2 reduction.