Quenching-induced surface engineering of ZnCo2O4 spinel oxide for enhanced oxygen evolution reaction

Exploring cost-effective and high-performance electrocatalysts for oxygen evolution reaction (OER) is quite significant for utilizing renewable energies by converting them to green hydrogen energy. ZnCo2O4 spinel oxide has drawn a wide attention in water electrolysis field owing to its earth abundance, low cost and eminent electrocatalytic activity. However, it still has a great room to boost its OER catalytic activity due to the low electrical conductivity and restricted active sites of ZnCo2O4 catalyst. Herein, a facile, easy-scalable and environmental-friendly quenching method is exhibited to achieve surface Fe doped and oxygen vacancy generated ZnCo2O4 by instantaneous cooling in Fe(NO3)3 solution. As a result, the quenched ZnCo2O4 catalyst shows a vastly improved OER activity in alkaline electrolyte, only requiring an overpotential of 332 mV to reach 10 mA cm-2, which is much lower than that of un-quenched ZnCo2O4 (405 mV). Our results manifest that quenching treatment can endow an active Fe amorphous layer, a higher ratio of Co3+ states and more abundance oxygen vacancies for ZnCo2O4 spinel oxide, thus possessing a higher OER activity. Our work offers an effective path for the regulation of metal oxides and its application in energy catalysis field.