Converting inert AlOOH into efficient electrocatalyst for oxygen evolution reaction via structural/electronic modulation.

Efficient and stable water-splitting electrocatalysts play a key role to obtain green and clean hydrogen energy. However, only a few kinds of materials display an intrinsically good performance towards water splitting. It is significant but challengeable to effectively improve the catalytic activity of inert or less active catalysts for water splitting. Herein, we present a structural/electronic modulation strategy to convert inert AlOOH nanorods into catalytic nanosheets for oxygen evolution reaction (OER) via ball milling, plasma etching and Co doping. Compared to inert AlOOH, the modulated AlOOH delivers much better OER performance with a low overpotential of 400 mV at 10 mA cm and a very low Tafel slope of 52 mV dec, even lower than commercial OER catalyst RuO. Significant performance enhancement is attributed to the electronic and structural modulation. The electronic structure is effectively improved by Co doping, ball milling-induced shear strain, plasma etching-caused rich vacancies; abrupt morphology/microstructure change from nanorod to nanoparticle to nanosheet, as well as rich defects caused by ball milling and plasma etching, can significantly increase active sites; the free energy change of the potential determining step of modulated AlOOH decreases from 2.93 eV to 1.70 eV, suggesting a smaller overpotential is needed to drive the OER processes. This strategy can be extended to improve the electrocatalytic performance for other materials with inert or less catalytic activity.