Enhanced piezoelectric-effect-assisted photoelectrochemical performance in ZnO modified with dual cocatalysts

Promising strategies are of great significance for designing photoelectrodes with high charge separation efficiency and low charge recombination rate in photoelectrochemical (PEC) water splitting. In this paper, we firstly propose a method of combining piezoelectric effect with photoelectrochemical cell by utilizing of direct band gap metal-oxide semiconductor ZnO as the photoanode. After introducing piezoelectric effect resulted from ultrasonic vibrations, the current density value reaches 0.45 mA.cm(-2) at 1.23 V-RHE by the production of strain-induced charge and the enhancement of the electric field, 1.7 times higher than that of ZnO without ultrasonic vibrations (0.27 mA.cm(-2) at 1.23 V-RHE). The deposition of spatially separated dual cocatalysts, of which the bottom Pt act as electron collection and transport layer while the outmost Co-Pi serve as hole-transfer layer, further facilitates the separation of charge (strain-induced and photogenerated) and accelerates the reaction kinetics. The utilization of dual cocatalysts efficiently improves the performance of photoanodes and leads to a current density of 0.80 mA.cm(-2) at 1.23 V-RHE, 1.8 and 3.0 times higher than the values of ZnO with and without ultrasonic vibrations. The strategy provides a promising method and idea for the manufacture of practical and high-performance electrodes.