Solar-Driven Cobalt-Encapsulated Carbon Nanosphere as an Efficient Electrocatalyst for the Oxygen Evolution Reaction

The progress of non-noble-metal-based electrocatalysts for hydrogen production as a renewable energy has attracted significant interest. Sugar carbon synthesized from the cost-effective hydrothermal strategy was employed as a substrate for metal doping to prepare Co@CNSx (Co@CNS50, Co@CNS100, and Co@CNS150) with Co2(OH)2CO3 by the simple solvothermal method. In 1.0 M KOH, Co@CNS100/GC required 301 mV to split water, and the Tafel value (90 mV dec–1) became lower than that of IrO2 (351 mV; 114 mV dec–1). In nickel foam, Co@CNS100/NF exhibits a small overpotential of 251 mV at 10 mA cm–2 and stability for 120 h with 3% potential loss. The excellent oxygen evolution reaction (OER) efficiency has been shown by Co@CNS100, which has adequate kinetics to address the sluggish water oxidation. The spherical morphology of Co@CNS100 assisted the ion transportation and minimized the traffic congestion to enhance the efficiency during the electrochemical process. Further, the solar water electrolyzer splits water at 1.55 V, which confirmed the effectiveness of Co@CNS100 for the solar to hydrogen (STH) production process. Hence, Co@CNS100 was recommended to generate large-scale hydrogen at a low cost.