Cd vacancies and Pt-Pd single atoms induced symmetry breaking in CdS for efficient piezo-photocatalytic hydrogen evolution

Developing efficient piezo-photocatalysts through integrating cation vacancies with double metal single atoms is vitally important for hydrogen production, while it remains a challenge. In this work, cadmium vacancy (V Cd ) as well as Pt and Pd single atoms (Pt-Pd) were simultaneously introduced into CdS to construct V Cd -CdS/Pt-Pd catalysts for piezo-photocatalytic hydrogen evolution. In-depth characterizations and DFT calculations confirmed that the symmetry breaking caused by V Cd , Pt-Pd dual single atoms and ultrasonic could induce the polarization enhancement and charge asymmetric distribution, modulate the density of electronic states as well as optimize the adsorption of H* intermediates. Under light and ultrasound, the optimal V Cd -CdS/Pt 0.20 -Pd 0.30 achieved the piezo-photocatalytic hydrogen evolution rate of 104.4 mmol g −1 h −1 , which was 10.0 and 30.7 times that of V Cd -CdS and CdS, respectively. The significant improvement of piezo-photocatalytic performance was due to the synergistic interaction of V Cd -CdS, Pt-Pd double single atoms and the ultrasonic-induced external stress, which enhanced the polarized electric field in V Cd -CdS/Pt-Pd and promoted the separation and transfer of photo-generated charges. Moreover, the piezoelectric polarization induced by ultrasonic could tilt the energy band and produce a stronger reduction potential, also facilitating the hydrogen evolution reaction. On the whole, the symmetry breaking achieved by structure modifications coupled with external stress effectively boosted the piezo-photocatalytic hydrogen evolution performance, which provided a reference for the design of high-efficiency piezo-photocatalysts based on vacancy engineering and double single atoms doping.