Activating Inert Crystal Face via Facet-Dependent Quench-Engineering for Electrocatalytic Water Oxidation

Developing a facile strategy to activate the inert crystal face of an electrocatalyst is critical to full-facet utilization, yet still challenging. Herein, the electrocatalytic activity of the inert crystal face is activated by quenching Co₃O₄ cubes and hexagonal plates with different crystal faces in Fe(NO₃)₃ solution, and the regulation mechanism of facet-dependent quench-engineering is further revealed. Compared to the Co₃O₄ cube with exposed {100} facet, the Co₃O₄ hexagonal plate with exposed {111} facet is more responsive to quenching, accompanied by a rougher surface, richer defect, and more Fe doping. Theoretical calculations indicate that the {111} facet has a more open structure with lower defect formation energy and Fe doping energy, ensuring its electronic and coordination structure is easier to optimize. Therefore, quench-engineering largely increases the catalytic activity of {111) facet for oxygen evolution reaction by 13.2% (the overpotential at 10 mA cm^-2 decreases from 380 to 330 mV), while {100} facet only increases by 7.6% (from 393 to 363 mV). The quenched Co₃O₄ hexagonal plate exhibits excellent electrocatalytic activity and stability in both zinc-air battery and water-splitting. The work reveals the influence mechanism of crystal face on quench-engineering and inspires the activation of the inert crystal face.