以具有抗积碳与氧还原活性的氮掺杂银/氮化铁/晶态碳为阴极的微生物燃料电池产电机制

In the wastewater treatment process, the heterotrophic microorganisms (biocarbon) in single–chamber microbial fuel cell (MFC) can make use of the substrates to form biofilm on the cathode surface, which will change it into a strong O2 competitor. The biocarbon may also inhibit the proton migration and the anode’s electron transfer, which results in the decrease of O2 reduction reaction (ORR) efficiency and catalytic activity of cathode catalysts. In this project, melamine with polar functional groups is selected as carbon (nitrogen) source, and based on the charge matching principle, the graphitized assitant (Fex+) and functional ingredients (Ag+) are added to the synthesis system. By using the method of carbothermal reduction with enhanced in situ nitrogen doping, nitrogen–doped silver/iron nitride/partily–graphitized carbon (Ag/FexN/NGC) composites can be simutaneously synthesized through converting Fe3C to FexN. This study aims to prepare the cathode catalyst with the characteristics of bio–carbon inhibition and high ORR efficiencies, which can change the unfavorable restrictions of the surface ORR on cathode, thereby improving the MFC power output. By restraining the activity of the respiratory enzyme of bactria and damaging the bacterial structure, effect of the generated reactive oxygen (ROS) on property of bio–carbon inhibition is discussed. Influence of the crystalline type and structure of Ag/FexN/NGC on property of bio–carbon inhibition is also explored. Based on the analysis of catalytic activity and pathway for ORR by using Ag/FexN/NGC, mechanism for the enhancement of catalytic reduction activity and electron transport by using the synergistic effect between Ag and FexN is investigated. By combining the process of ROS consumation (by bio–carbon inhibition) with the process of ORR on active centers of the catalyst, electricity generation mechanism for MFC with ORR–enhanced Ag/FexN/NGC cathodes can be revealed.

在单室微生物燃料电池（MFC）处理污水过程中，异养微生物会在阴极形成生物膜（积碳），成为O2竞争体，使O2还原反应（ORR）效率降低。本项目以三聚氰胺为碳（氮）源，引入石墨化助剂（Fex+）和功能性组分（Ag+），通过强化原位氮掺杂促进碳化铁向氮化铁转化而同步碳热还原合成银/氮化铁/晶态碳（Ag/FexN/NGC）材料，利用其抗积碳与高效O2还原的协同作用，改善ORR的不利限制而提高MFC功率输出；以抑制细菌呼吸酶活性和破坏细胞结构为目标，分析活性氧对生物膜生成的拮抗作用，阐明Ag/FexN/NGC的组成与结构对抗积碳性能的影响；基于对Ag/FexN/NGC的ORR催化性能与途径分析，阐释FexN和Ag之间协同作用对ORR催化活性与电子转移能力的增强机理；将Ag/FexN/NGC阴极表面抗生物积碳的活性氧消耗过程与催化剂活性中心ORR过程有机结合，揭示此ORR性能强化的MFC的产电机制。

在单室微生物燃料电池（MFC）处理污水过程中，异养产电微生物会在阴极表面形成生物膜（积碳），并成为O2竞争体，使O2还原反应（ORR）效率降低；因此，探索有微生物耗氧干扰的O2还原反应（ORR）过程对于了解MFC的微生物催动的电催化过程来说具有重要意义；本项目以玉米秸秆作为碳源，通过与银源、铁源和三聚氰胺螯合，碳化后制备出银/铁/氮/碳（Ag/Fe/N/C）复合材料，并将其用作MFC的抗菌ORR催化剂。研究了不同碳化温度对Ag/Fe/N/C碳骨架的石墨化程度（导电性）、纳米Ag的尺寸、N物种组成（吡啶氮、石墨化氮、Fe−Nx等）以及比表面积的影响；探讨了物相组成、形貌以及孔隙结构对ORR催化活性的影响，分析了催化剂的物化性质与H2O2生成量、电子转移途径、催化活性和抑菌稳定性之间的相互关系。在630℃碳化得到的Ag/Fe/N/C材料具有最大的功率密度（1791mW•m−2），高于商业铂碳的功率密度（1192mW•m−2）；其在90天的运行期内仅衰减了16.14%，表现出了良好的抗生物积碳和ORR稳定性。其中，Ag/Fe/N/C材料中的Fe−Nx键以及吡啶氮和吡咯氮的协同作用都有助于提高ORR的催化活性。由纳米Ag氧化物缓释得到的Ag+去破坏产电细菌细胞膜的通透性，或由纳米Ag与细菌细胞蛋白质中的基团（巯基或氨基）作用而降低细胞活性，从而抑制生物膜在Ag/Fe/N/C阴极上的生长，减少生物膜对电子转移内阻与稳定性的影响；Ag/Fe异质结构和N组分的协同作用极大的有助于提高空气阴极MFC的功率密度以及库伦效率。本课题将Ag/Fe/N/C阴极中纳米Ag的抗生物积碳作用与催化剂ORR过程结合，揭示了阴极性能被强化的MFC的产电机制。