Activating Metal Oxides Nanocatalysts for Electrocatalytic Water Oxidation by Quenching-Induced Near-Surface Metal Atom Functionality.

Developing a reliable strategy for the modulation of the texture, composition, and electronic structure of electrocatalyst surfaces is crucial for electrocatalytic performance, yet still challenging. Herein, we develop a facile and universal strategy, quenching, to precisely tailor the surface chemistry of metal oxide nanocatalysts by rapidly cooling them in a salt solution. Taking NiMoO4 nanocatalysts an example, we successfully produce the quenched nanocatalysts offering a greatly reduced oxygen evolution reaction (OER) overpotential by 85 mV and 135 mV at 10 mA cm-2 and 100 mA cm-2 respectively. Through detailed characterization studies, we establish that quenching induces the formation of numerous disordered stepped surfaces and the near-surface metal ions doping, thus regulating the local electronic structures and coordination environments of Ni, Mo, which promotes the formation of the dual-site active and thereby affords a low energy pathway for OER. This quenching strategy is also successfully applied to a number of other metal oxides, such as spinel-type Co3O4, Fe2O3, LaMnO3, and CoSnO3, with similar surface modifications and gains in OER activity. Our finding provides a new inspiration to activate metal oxide catalysts and extends the use of quenching chemistry in catalysis.