三维有序微介孔钒基固溶体光催化还原CO2及产物可控机制研究

Photocatalytic reduction of CO2 to produce hydrocarbon fuels has been considered to be an important way to solve the problems of both environmental issue and future energy supply in the world. Aiming to some key problems in the photocatalytic reduction of CO2 research such as low photocatalytic activity and selectivity, ultraviolet(UV) photoresponse only, this project is proposed based on BixY(1-x)VO4 solid solutions with controllable energy bands. The three-dimensional ordered micro-mesoporous photocatalysts with low defect density and large specific area are synthesized using mesoporous SiO2 spheres arranged on a two-dimensional hexagon cubic as templates and loaded co-catalysts in order to improve the photocatalytic activity and selectivity. The solid solutions with different morphologies and crystalline quality are obtained by controlling the particle size, pore size of SiO2 and calcination temperature. Then their photocatalytic activity for CO2 reduction is investigated to establish the relationship of the physical property and activity of photocatalysts. The effect of the constituent, morphology, particle size of co-catalysts on separating photogenerated carriers and reducing product overpotential is studied to clarify the mechanism that cocatalysts influence the photocatalytic activity and slectivity, thus establishing the relationship of the physical property of photocatalyst and co-catalyst with photocatalytic activity and selectivity. This project will not only enrich the systems of photocatalytic materials for reducing CO2, but provide an idea for developing new high-efficiency photocatalytic reduction CO2 materials as well.

半导体光催化还原CO2制备碳氢燃料对解决当今世界面临的能源和环境问题具有重要意义。本项目针对目前光催化CO2还原研究中催化剂活性低、产物选择性差、仅响应紫外光等问题，提出以能带可控的BixY(1-x)VO4 固溶体材料为基点，利用二维六方排布介孔SiO2作为模板合成低缺陷密度、高比表面积、能带满足CO2还原电位的三维有序微介孔可见光催化材料，结合助催化剂，提高反应的活性及实现产物的可控性。调控SiO2的粒径、孔径及焙烧温度获得不同形貌、结晶度的固溶体材料，并进行CO2还原研究，建立催化剂物性—活性关系；考察助催化剂的组分、形貌、粒径对分离光生载流子和降低还原过电位能力的影响，揭示助催化剂影响活性和选择性的机制，从而构建催化剂和助催化剂的物性结构与活性、选择性的关系。本项目不仅能丰富高活性的光催化还原CO2材料体系，而且为未来开发新型高效光催化材料提供思路。

半导体光催化还原CO2制备碳氢燃料对解决当今世界面临的能源和环境问题具有重要意义。本项目利用固相法合成BixY(1-x)VO4 (x=0.1~0.6) 固溶体光催化剂，通过改变组分(Bi/Y)调节能带位置并进行光催化CO2还原，揭示能带结构/位置对CO2还原活性的影响。采用光沉积法将金属（Ag, Pd, Au）或金属氧化物（Cu2O）助催化剂负载于H2SrTa2O7的表面并进行CO2还原研究。证实了助催化剂由于具有不同的析CO和H2的过电位而影响其选择性，具有较低CO析出过电位的助催化剂负载可以有效提升光催化剂的选择性。另外，利用SiO2硬模板法合成了高比表面积和高结晶度介孔Bi0.5Y0.5VO4固溶体光催化剂并用于CO2还原研究。 虽然由于NaOH去除SiO2过程中，固溶体表面的Y被侵蚀，使得活性不高。然而依据该思想，成功合成了高比表面积、高结晶度的介孔Ta2O5及TiO2,显示具有体相更高的CO2还原活性，说明利用模板剂制备高比表面积和高结晶度光催化剂是提高光催化活性的有效途径。在本项目的支持下，同时进行了利用SiO2硬模板制备大比表面积、高活性介孔g-C3N4, 并且在Z型体系下完成可见光完全分解水，其420 nm下量子效率达到1.8%。考虑到光催化还原CO2过程首先进行H2O的氧化以提供质子，因此对CO2还原研究具有指导意义。