Fabrication of Co2RuS6/CdS Z-scheme heterojunction with sulfur vacancy for enhanced piezo-photocatalytic H2 evolution and in-depth analysis of charge-separation mechanism

Abstract

The current photocatalytic hydrogen production performance is still limited by severe electron hole recombination. Notably, non-centrosymmetric piezoelectric materials could generate piezoelectric fields by mechanical forces to that promote the separation of photogenerated charges. Therefore, the combination of piezocatalysis and photocatalysis is expected to greatly promote the hydrogen production performance. In this work, a novel Z-type heterojunction Co2RuS6/CdS with sulfur vacancies (CRS/CdS-30) piezo-photocatalytic material was firstly primaried to boost H2 production activity. 10 % CRS/CdS-30 composite catalyst reached an impressive hydrogen production rate as 110.66 mmol·g−1·h−1 into combined effect of light and ultrasound, which was higher than the sum of pure photocatalytic (72.97 mmol·g−1·h−1) and pure piezoelectric performance (0.86 mmol·g−1·h−1). Moreover, H2 production rate for CRS/CdS-30 is 24, 14 and 15 times that of pure CdS, 10 % Co9S8/CdS-30 and 10 % RuS2/CdS-30, respectively. It has been confirmed through various characterization methods that: (1) The presence of sulfur vacancies greatly increases the catalytic active sites; (2) The transfer of photogenerated charges in the CRS/CdS-30 heterojunction follows the Z-scheme; (3) The piezoelectric field in CdS eliminates electrostatic shielding and tremendously enhances the separation efficiency of electron-hole pairs. This study supplies a new approach for constructing efficient piezo-photocatalytic materials.