Synthesis of Co/Ni @ Al2O3-GO as novel oxygen reduction electrocatalyst for sustainable bioelectricity production in single-chambered microbial fuel cells

Abstract In this work, the synthesis of cobalt (Co) -nickel (Ni) nanoparticles supported on the matrix of alumina-graphene oxide (Al2O3-GO) and studies of their oxygen reduction reaction (ORR) activity in single-chambered microbial fuel cells (MFCs) were reported. A study of different weight ratios of Co-Ni nanoparticles with support material is accomplished to determine the catalyst performance. It is revealed that the catalyst Co-Ni (2:1)/Al2O3-GO (catalyst S2) with a weight ratio of 2:1 of nanoparticles shows optimized properties among other electrocatalysts. The ORR study of hybrid catalysts suggested that the catalyst S2 (reduction potential at 542 mV with −0.252 mA current) showed higher stability and electrocatalytic activities compared to catalyst Pt/C (reduction potential at 466 mV with −0.210 mA current) towards ORR. Al2O3-GO supported Co-Ni (2:1) catalyst revealed an improved ORR rate in single-chambered MFCs with a maximum power density of ~168 mW/m2 compared to 102 mW/m2 for Pt/C. The enhanced electrocatalytic activity of catalyst S2 was accredited to the high electronic conductivity and longer stability of the nanocomposite. MFCB (catalyst S2) showed the highest OCV values (668 ± 15 mV), corresponding to the maximum electrochemical activity. Higher OCV values signified a stable biofilm developed on anode surface resulting in high electron transfer from microbes to anode surface, leading to maximum power production by catalyst S2 in MFCB. The experimental consequences confirmed the employments of Al2O3-GO as a beneficial support matrix in constructing inexpensive and efficient cathode catalysts over standard Pt/C catalysts for single-chambered MFCs.