Electrochemically Fabricated Superhydrophilic/Superaerophobic Manganese Oxide Nanowires at Discontinuous Solid–Liquid Interfaces for Enhanced Oxygen Evolution Performances

The design of an electrode surface is critical to the oxygen evolution reaction (OER) during electrochemical water splitting since the catalytic activity depends strongly on surface characteristics, such as the coating uniformity of the catalysts, electrolyte wetting, and the gas-bubble release ability. Here, nonprecious-metal electrocatalysts (MnO nanowires) are electrochemically deposited on the surface of a porous gold microgrid. The discontinuous solid–liquid contact lines, which are formed by the microgrids during the liquid-phase electrochemical reaction, generate MnO nanowires with high coating uniformity. The micro/nanostructure of the electrode induces a superhydrophilic surface, which facilitates the wetting of the alkaline electrolyte and increases the electrochemical active surface area. Simultaneously, the underwater superaerophobicity of the electrode promotes the release of the oxygen products, thus reducing the occupation of the catalytic sites by the gas bubbles. The synergistic effect of electrolyte wetting and gas release ensures that this superhydrophilic/superaerophobic electrode exhibits a current density of 10 mA cm⁻² for the OER at an overpotential of 530 mV in 0.1 m KOH, placing the catalyst among the best MnO catalysts for OER. This work avails a new basis for synergistically optimizing the synthesis methods (electrolyte wetting and gas-bubble release) toward high-performance OER electrodes.