基于p型MOFs阴极的自偏压双光电极体系协同消减重金属-有机物复合污染

光电催化可以还原重金属同时氧化降解有机物，有望解决低浓度含铬污水因共存有机物和铬配位致难深度处理的瓶颈，但存在阴极电子还原六价铬的选择性低、传递速度慢及外加偏压增加能耗等问题。本项目在前期研究基础上，提出以可见光响应MOFs阴极取代铂/石墨等光惰性阴极，设计n型阳极-p型阴极的双光电极体系，形成类似于导线连接的Z-Scheme结构。利用阴、阳极费米能级差产生自偏压，驱动阳极电子补偿阴极空穴，实现高活性空穴和电子在阳、阴极的分别调控。重点开发和探索与光阳极（如钒酸铋等）能级匹配、表面性质稳定、对六价铬优先吸附-还原及快速脱附三价铬的p型MOFs阴极。探明污染物在电极表面的吸附位点、界面电子转移机理及速率限制步骤，找到促进底物吸附、释放活性位点、加速反应的电极修饰/改性方法。对双光电极体系进行优化调控，实现无外加偏压下、低浓度六价铬(<0.5mg/L)在有机污染物共存水体中的高效协同消减。

Photoelectrocatalysis can simultaneously reduce heavy metals and oxidatively degrade organic matters, which is expected to solve the bottleneck of deep treatment of low concentration chromium-containing wastewaters due to the coexistence of organic matters and chromium coordination. However, there are still many problems, such as low selectivity of cathodic electrons for the reduction of Cr(VI), slow transfer rate and increasing energy consumption by external bias voltage. On the basis of our previous studies, a dual-photoelectrode system with n-type anode and p-type cathode was proposed, based on using visible-light-responsive MOFs as cathode instead of light-inert platinum/graphite. In this way, Z-Scheme like structure can be formed via wire connection. Self bias can be generated due to the Fermi energy difference between the cathode and anode, which will drive the anode electrons to compensate the cathode holes, and realize the regulation of highly active holes and electrons in the anode and cathode, respectively. We will focus on developing and exploring p-type MOFs-based photocatalytic cathodes, which behave matchable energy levels to photoanodes (such as BiVO4), stable surface properties, preferential adsorption and reduction for Cr(VI) and fast desorption of Cr(III). The adsorption sites, the electron transfer mechanism and the rate limiting step will be studied. The ways of electrode modification will be explored for promoting substrate adsorption, releasing active sites and accelerating reaction. Through the optimization and regulation of the dual-photoelectrode system, highly effective and synergistic reduction of low concentration Cr(VI) (<0.5mg/L) in organic pollutant coexisting waters can be achieved under no external bias.