Water flow induced piezoelectric polarization and sulfur vacancy boosting photocatalytic hydrogen peroxide evolution of cadmium sulfide nanorods

Piezo-photocatalytic H2O2 production utilizing earth-abundant solar and mechanical energies, oxygen and water is a highly appealing route to produce renewable energy carriers. However, piezoelectric polarization always suffers from high-frequency mechanical vibration, which severely restricts its actual applications. Here, we report prominent piezo-photocatalytic H2O2 evolution from pure water triggered by low-frequency water flow induced mechanical stress over 1D CdS nanorods with sulfur vacancy (CdS NRs). The polar CdS NRs possess benign piezoelectric property and favorable morphology, enabling high sensitivity and respond to weak force of water flow, which contribute to yielding large piezoelectric polarization for photogenerated charges separation. Piezoelectric polarization also shows an inhibition effect on the photocorrosion of CdS to ·SO3-. Besides, DFT calculations demonstrate that sulfur vacancy allows enhanced O2 adsorption and formation of the intermediate *OOH on the surface of CdS. Under simultaneous visible light and high-speed stirring, CdS NRs display a remarkably synergetic piezo-photocatalytic H2O2 production (1631.4 µmol g−1 h−1) without any sacrificial agents, 2.4 and 73.8 times of that under sole visible light and mechanical agitation, respectively. Importantly, it achieves an apparent quantum efficiency (AQY) of 1.32% at wavelength up to 500 nm and a solar-to-chemical (STC) conversion efficiency of 0.05% under one-sun illumination, which far exceeds other reported sulfide-based catalysts. This work integrates well with polarization engineering, defect engineering and morphology engineering to enhance catalytic behavior, providing a feasible strategy for designing efficient piezo-photocatalysts sensitive to weak mechanical forces.