Oxygen vacancy engineering of zinc oxide for boosting piezo-electrocatalytic hydrogen evolution

Abstract

• The effect of oxygen vacancy concentration on piezo-electrocatalytic H 2 evolution over ZnO is systematically investigated by varying the annealing temperature. • Bifunctional improvement of carrier dynamics and surface reaction is achieved via oxygen vacancy engineering. • Constructing oxygen vacancy offers an effective approach to promote piezo-electrocatalytic H 2 evolution. Vibration-driven piezo-electrocatalytic hydrogen evolution reaction has drawn great interest in the past years as it provides an effective approach to harvest the dispersed and extensive mechanical energy. However, its wide applications remain a grand challenge due to the unsatisfied catalytic activity of currently available piezo-electrocatalysts. Here, the defect engineering is applied in the hydrothermally-synthesized ZnO by heat treatment to fabricate ZnO catalysts with various concentrations of oxygen vacancy . Under the stimulation of ultrasonic vibration, ZnO with optimal oxygen vacancy concentration shows a piezo-electrocatalytic H 2 yield of 3.8 mmol · h −1 · g −1 . The controlled experiments of piezo-current response and electrochemical impedance spectroscopy disclose that the piezo-generated carriers’ separation and transfer are greatly enhanced in ZnO after introducing oxygen vacancies. Density functional theory calculations uncover that the oxygen vacancies of ZnO play an important role in facilitating H desorption. This work delivers an efficient strategy to achieve the simultaneous improvement of carrier dynamics and surface reaction and ultimately promote piezo-electrocatalytic H 2 evolution.