Boride-mediated synthesis of a highly active cobalt-based electrocatalyst for alkaline hydrogen evolution reaction

The lack of viable means to simultaneously address intrinsic activity, density of active sites and electronic conductivity issues remains a grand challenge restricting the development of earth-abundant electrocatalysts for the alkaline hydrogen evolution reaction (HER). Herein, we report a boride-mediated synthesis method to address these issues. Our study found that a cobalt boride catalyst prepared by the chemical reduction method is actually an amorphous mixture of CoBx, CoO and B-containing impurities. Annealing treatment of this composite initiates a solid reaction between CoBx and CoO, leading to the formation of tiny Co nanoparticles on the surface of amorphous CoO/B2O3 nanosheets. Besides the creation of abundant accessible Co/CoO active sites for the alkaline HER, the annealing treatment can also help increase the specific surface area and improve the electrical conductivity. Benefiting from these favorable attributes, the post-annealed Co/CoO/B2O3/CF catalyst exhibited outstanding HER performance in an alkaline electrolyte. It required overpotentials of 16 and 100 mV to afford 10 and 100 mA cm(-2), respectively, and showed good stability in the long-term operation, outperforming the benchmark Pt/C.