Multiple synergies on cobalt-based spinel oxide nanowires for electrocatalytic oxygen evolution

Cobalt-based spinel oxides have excellent oxygen evolution reaction (OER) activities and are cheap to produce; however, they have limited commercial applications due to their poor electrical conductivities and weak stabilities. Herein, we soaked Co 3- x Ni x O 4 nanowires in NaBH 4 solutions, which endowed Co 3- x Ni x O 4 with significant oxygen vacancy content and decorated BO x motifs outside the Co 3- x Ni x O 4 nanowires. X-ray photoelectron spectroscopy and in situ Raman data suggest that these evolutions improved the conductivity, hydrophilicity, and increased active sites of the spinel oxides, which synergistically boosted their overall OER performances. This improved performance made the optimized BO x -covered Co 2.1 Ni 0.9 O 4 nanowires generate a current density of 10 mA cm −2 when used for the OER at an overpotential of only 307 mV, maintaining excellent stability at 50 mA cm −2 for 24 h. This study provides a facile method for designing cobalt-based spinel oxide OER catalysts.