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

NaBH4-treatment endows Co-Ni spinel nanowires with oxygen vacancies and boron-containing oxygen functional groups, which synergistically improve the conductivity, enlarge the amounts of reactive centers, and enhance the hydrophilicity, finally boosting the OER performance. [Display omitted] 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 Co3-xNixO4 nanowires in NaBH4 solutions, which endowed Co3-xNixO4 with significant oxygen vacancy content and decorated BOx motifs outside the Co3-xNixO4 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 BOx-covered Co2.1Ni0.9O4 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.