N-doped GO cathode catalyst boosting capacity of denitrification for air-cathode microbial fuel cell by shifting microbial community composition in treating marine wastewater

Abstract

Air-cathode microbial fuel cell (AMFC) is a promising technology with considerable potential for treating contaminants, while obtaining energy has gained a substantial interest. The oxygen reduction reaction (ORR) performance of the cathode electrode is the pivotal factor for boosting AMFC ability. In this study, nitrogen-doped GO cathodic catalysts were prepared using direct heat treatment (NGO) and one-step hydrothermal method (H-NGO). The electrochemical experiments showed the AMFC equipped with NGO10 (wt% of urea: GO was 10:1) achieved the highest output voltage of 391.8 mV with a power density of 1800 mWm-3 in comparison with H-NGO and Pt/C electrodes, i.e. The diversity of bacterial communities for different biofilms was analyzed using high-throughput sequencing, the result showed the relative abundance of denitrifying bacteria including Marinobacter (34.9 %), Methylophaga (4.6 %), Pseudidiomarina (2.7 %) and Glaciecola (3.0 %) significantly increased at cathodic biofilms, moreover, Marinobacter, Methylophaga and Arcobacter were enriched at NGO10 cathode electrode. Reconstruction of Unobserved States (PICRUSt2) predicted differences in metabolic pathways between anode and cathode biofilm, indicating that L-threonine metabolism was significantly down-regulated, while spirilloxanthin, 2,2′-diketo-spirilloxanthin biosynthesis and syringate degradation were significantly up-regulated. A real-time PCR (RT-PCR) represented the genes related to denitrification involving napA, nirK, nirS, nosZ and norB possessed relative higher expression in NGO10 cathode biofilm.