Strong-Coupled Cobalt Borate Nanosheets/Graphene Hybrid as Electrocatalyst for Water Oxidation Under Both Alkaline and Neutral Conditions

Developing highly active catalysts for the oxygen evolution reaction (OER) is of paramount importance for designing various renewable energy storage and conversion devices. Herein, we report the synthesis of a category of Co-Pi analogue, namely cobalt-based borate (Co-Bi) ultrathin nanosheets/ graphene hybrid by a room-temperature synthesis approach. Benefiting from the high surface active sites exposure yield, enhanced electron transfer capacity, and strong synergetic coupled effect, this Co-Bi NS/G hybrid shows high catalytic activity with current density of 10 mAcm -2 at overpotential of 290 mV and Tafel slope of 53 mVdec -1 in alkaline medium. Moreover, Co-Bi NS/G electrocatalysts also exhibit promising performance under neutral conditions, with a low onset potential of 235 mV and high current density of 14.4 mAcm -2 at 1.8 V, which is the best OER performance among well-developed Co-based OER electrocatalysts to date. Our finding paves a way to develop highly active OER electrocatalysts.