Cobalt coordination controlled carbon nanospheres formation and inclusion of amorphous Co3O4 and AuNPs: strongly enhanced oxygen evolution reaction with excellent mass activity.

Abstract

Carbon nanospheres integrated with AuNPs and amorphous Co3O4 were fabricated by making use of cobalt coordination with AuNP surface ligands, which exhibited an enhanced oxygen evolution reaction (OER) with excellent mass activity. Co2+ coordination with AuNP surface functional molecules significantly influenced the nanostructure formation and OER activity. Nanospheres of carbon with an optimum concentration of AuNPs and Co3O4 (2) showed strong OER activity. 2 exhibited a high current density (358 mA cm-2 at an applied potential of 1.59 V) and required a low overpotential (256 mV) to generate a geometric current density (10 mA cm-2) compared to commercial RuO2 (363 mV). Importantly, 2 showed high mass activity (1352.5 mA mg-1), 14 times higher than RuO2 (93.87 mA mg-1). The low Tafel slope (52.4 mV dec-1) and charge transfer resistance along with large double layer capacitance (Cdl = 20.1) of 2 suggest strong electronic communication between the catalyst and the electrode surface and facilitated fast charge transport. Chronoamperometric studies confirmed the excellent stability of the catalyst. The present work demonstrates that the electrocatalytic activity of earth-abundant amorphous metal oxides can be strongly enhanced by integrating metallic nanoparticles (NPs) and optimizing nanostructures.