氮掺杂诱导Co-Sex活性位点暴露促进MFC中硝酸根催化还原的电子传递途径解析

Nitrate (NO3--N) is one of the key factors for water eutrophication. Higher overpotential, inefficient electron availability and utilization limit the electro-catalytic reduction efficiency of NO3--N. In this study, the electricity generation of single-chamber microbial fuel cell (SC-MFC) is coupled with the electro-catalytic process. NO3--N as the shared electron acceptor is added to the SC-MFC with O2 as the initial electron acceptor. Cobalt selenide/N-doped partly-graphitized carbon (CoSe2/NPGC) polyhedron material as the cathode catalyst is prepared from the ZIF-67 dodecahedron and abundant N-induced surface defects (Co-Sex) on CoSe2/NPGC are formed by in-situ selenization of Co. The effects of structure and active components of CoSe2/NPGC on the NO3--N reduction efficiency, the formation of byproducts (NO2--N, NH3, etc) and the electricity generation are investigated. The activity and stability of NO3--N reduction on CoSe2/NPGC cathode is explored in the co-existence of NO3--N and ORR. According to the electricity generation performance and coulombic efficiency during the degradation of organic wastewater in SC-MFC, the dynamic correlations between NO3--N reduction and ORR are studied. Therefore, the decontamination functions of SC-MFC may be expanded and the electron transfer pathway and the reduction mechanism should be obtained when the NO3--N reduction and ORR are simultaneously conducted in SC-MFC.

硝酸盐氮（NO3--N）是水体富营养化的关键因子之一；高过电位和低效电子利用限制了NO3--N的电催化还原效率。本项目将单室微生物燃料电池（SC-MFC）产电与电催化过程耦合，在以O2为电子受体的SC-MFC中加入NO3--N为共同电子受体；以ZIF-67十二面体为骨架结构、通过钴（Co）中心原位硒化合成的N掺杂诱导表面缺陷（Co−Sex）丰富的二硒化钴/N掺杂石墨化碳（CoSe2/NPGC）为阴极催化剂；考察CoSe2/NPGC结构与活性组分对SC-MFC中NO3--N还原效率、副产物（NO2--N、NH3等）及产电性能的影响；探索与氧还原反应（ORR）共存时，NO3--N在CoSe2/NPGC上还原的活性和稳定性；根据降解有机废水时的产电性能与库伦效率，归纳出NO3--N还原与ORR之间的动态关联，扩展SC-MFC除污染功能，获得NO3--N还原与ORR共存时的电子转移途径与还原机理。

水体中硝酸盐氮（NO3--N）的存在可能导致严重的环境问题，NO3--N的电催化还原需要一个较高的电势和高效的电子利用率；这就需要一个催化还原NO3--N活性高的催化剂来持续消耗电子，以克服催化过程产生的过电势。（1）通过原位Se化的方法，在不同温度下合成有氧气还原（ORR）或生成反应（OER）活性的CoSe（与NiSe协同）基材料，并通过CoSe/NiSe基催化剂结构的表征、电化学性能优化，使其具有理想的电催化还原活性和稳定性。（2）将MFC过程与电催化还原过程耦合，获得了以Fe3Se4/FeSe基催化剂材料为阴极的MFC降解有机废水的产电性能（1003mW/m2）与库伦效率（25%以上），归纳出ORR与产电性能之间关系的规律性结果，从而扩展MFC的除污染功能，同时发现了电子转移过程为4电子途径。（3）基于ZnO材料具有良好的生物相容性和高OER电位等特点，采用溶剂热-烧结法制备了表面催化活性较高的ZnO/纳米石墨（Nano-G）材料，研究了制备条件对ZnO/Nano-G催化剂结构和性质的影响；并基于电化学性能测试，利用热压法将优选的ZnO/Nano-G材料制备为阴极，对水中NO3--N（100mg/L）的还原效率可以达到82.5%以上，且总氮去除效率在70%以上。