在CuFeO2纳米簇/CuInS2薄膜复合电极上CO2光电催化还原反应研究

Nowadays, the formation rate of methanol is low in photoelectrocatalytic reduction of carbon dioxide to methanol. In this study, CuFeO2 nanocluster/CuInS2 thin film composite photocathode is suggested to enhance the rate of CO2 reduction and the selectivity of methanol in photoelectrocatalytic reduction of CO2..Firstly, CuFeO2 nanocluster/CuInS2 thin film composite electrode is fabricated by electrodepositing CuFeO2 nanoclusters on CuInS2 thin film electrode. The effect of fabrication technology on the particle size, coverage, crystal structure and lattice defect of the nanoclusters is studied, and the influence of the structure of the composite electrode on its surface electronic structure is investigated. Secondly, the dependence of the onset potential and the rate of CO2 reduction on the composite electrode structure is examined. The effect of the local coordination structure around the atoms in CuFeO2 nanoclusters and the surface electronic structure of the composite electrode on the charge transfer and the mass transfer in CO2 reduction reaction is studied, the mechanism for regulating the rate of CO2 reduction is therefore elucidated. Furthermore, the influence of the composite electrode structure and pyridine co-catalyst on the selectivity of methanol is studied. The quantity of adsorbed hydrogen on the composite electrode surface is regulated by the local coordination structure around the atoms in CuFeO2 nanoclusters and the surface electronic structure of the composite electrode, then the relationship between the adsorbed hydrogen quantity and the Faradic efficiency of methanol is established, the mechanism for regulating the selectivity of methanol is therefore revealed. Finally, the stability of the composite electrode is examined.

目前，CO2光电催化还原为甲醇的速率较低。本研究以CuFeO2纳米簇/CuInS2薄膜复合电极为光阴极，进行CO2光电催化还原，提高CO2还原速率和甲醇选择性。.在CuInS2薄膜电极上电沉积CuFeO2纳米簇，制备CuFeO2纳米簇/CuInS2薄膜复合电极，探讨制备过程对纳米簇粒径、覆盖度、晶体结构和晶格缺陷的影响，以及复合电极结构对其表面电子结构的影响。研究CO2还原电位、还原速率随复合电极结构的变化规律；探讨纳米簇中原子的局域配位结构、复合电极表面电子结构对CO2还原过程电荷转移、传质的影响，阐明CO2还原速率的调控机制。研究复合电极结构、吡啶共催化剂对甲醇选择性的影响，通过调控纳米簇中原子的局域配位结构、复合电极表面电子结构来调控复合电极表面吸附氢数量，建立吸附氢数量与甲醇的法拉第效率之间的关系，揭示甲醇选择性影响机理。最后，研究复合电极的稳定性。

可见光照射下将CO2光电催化还原为太阳能燃料甲醇，将太阳能转化为化学能，对于减少CO2排放，缓解能源紧缺的状况，具有十分重要的意义。本项目构建了CuFeO2纳米簇/CuInS2薄膜复合电极，研究了复合电极结构对CO2光电催化活性、稳定性、甲醇选择性的影响，阐明了CO2还原速率调控机制，揭示了甲醇选择性影响机理。采用差分脉冲电沉积法、模板法和限域电沉积法三种方法在CuInS2薄膜表面制备了CuFeO2纳米簇，其中模板法和限域电沉积法得到的CuFeO2纳米簇粒径更均匀，并形成了氧空位。由于CuInS2表面与CuFeO2纳米簇的相互作用，以及氧空位的形成，造成表面铜电子结构的改变。与CuInS2薄膜相比，CuFeO2纳米簇/CuInS2薄膜在可见-近红外范围的光吸收增强，带隙有所增大，光生电子-空穴的复合受到明显抑制。以CuFeO2纳米簇/CuInS2薄膜复合电极为光阴极，可见光照射下，在较低过电位下可将CO2高选择性还原为甲醇。与CuInS2薄膜电极相比，CuFeO2纳米簇/CuInS2薄膜复合电极对CO2还原具有更高的催化活性。复合电极催化活性的提高主要是由于CuFeO2与CuInS2形成p-p异质结，光生电子-空穴的复合受到抑制，以及新活性中心（CuFeO2）的引入。对复合电极上CO2还原的电极过程动力学研究表明，传质阻力是决速步骤，而传质阻力与吡啶在电极表面的覆盖度关系密切。富铜的复合电极表面提高了甲醇选择性。对CO2还原过程吸附态中间体的研究表明，甲醇产率随电极表面吸附态CO覆盖度的增加而提高，而与吸附态氢覆盖度没有明显关系。复合电极上吸附态氢的形成受到抑制，因而析氢反应受到抑制。复合电极在9 h内具有高稳定性。本项目的实施，对CO2减排与资源化利用具有重要的科学价值与社会意义。