Enhanced power generation using nano cobalt oxide anchored nitrogen-decorated reduced graphene oxide as a high-performance air-cathode electrocatalyst in biofuel cells

Abstract

So far, the effect of the carbon matrix on ORR catalytic efficiency over carbon/cobalt oxide nanohybrids in biofuel cells has not been investigated, which is vital to guiding the scientific research on ORR catalysts. Moreover, although cobalt oxide crystals have been reported with electrocatalytic activity, studies on square-like nano cobalt oxide are very few, and it has not been reported as an oxygen reduction reaction (ORR) catalyst, let alone used in biofuel cells. Thus, herein, square-like nano cobalt oxide anchored on nitrogen-doped graphene (NG/Co-NS), carbon nanotube (CNT/Co-NS) and carbon black (CB/Co-NS) were prepared by a one-pot hydrothermal method for the application as an ORR catalyst in microbial fuel cells (MFC). The results indicated that NG/Co-NS exhibited outstanding ORR activity with a more positive on-set potential (−0.05 V vs. Ag/AgCl) and higher limiting diffusion current (5.8 mA cm⁻² at −0.8 V) than CB/Co-NS and CNT/Co-NS, attributed to the synergistic catalytic effect of NG and Co-NS. Besides, in MFC tests, the maximum power density of NG/Co-NS was improved significantly to 713.6 mW m⁻², which was 24.9% higher than Pt/C (571.3 mW m⁻², 0.2 mg Pt cm⁻²). In addition, the internal resistance of MFCs with NG/Co-NS was lower than CB/Co-NS and CNT/Co-NS, which favored the electricity generation performance. Thus, NG/Co-NS was promising material for an alternative oxygen reduction reaction electrocatalyst of Pt/C in MFCs.