Restoration mechanism of photocatalytic H2O2/H2 production stability of ZnO/ZnS S-scheme heterojunction

Abstract

Sulfide photocatalysts are one of the widely recognized excellent photocatalysts. However, the stability of sulfide photocatalysts has always been a challenging problem in the field of photocatalysis. Herein, an in-situ oxidation strategy was designed to construct ZnO/ZnS homologous S-scheme catalysts and solve its poor stability problem. The results indicates that the obtained ZnO/ZnS homologous heterojunction not only has dual-function performance, but also has good recover ability in photocatalytic performance: the photocatalytic H₂O₂ yield can reach 517.32 μmol g^–1 (in pure water) after two hours, the photocatalytic H₂ yield is 140.45 mmol g^–1 in 5 h, which were 2.2 times and 84 times than that of the ZnS, respectively. Excitingly, the recovery rate of photocatalytic performance can be increased from 33.3% to 97.2%. The excellent photocatalytic performance is attributed to that the obtained homologous heterojunction can not only broaden the light absorption capacity (370–600 nm), but also facilitate the separation and transfer of photogenerated electrons. The high recovery rate of photocatalytic stability is due to the re-generation of zinc oxide in the oxidation process, which makes the photocatalyst return to the original homologous heterojunction structure. Meanwhile, experimental results, density functional theory calculations and Kelvin probe force microscopy indicate that the photo-induced carrier transfer pathway follows the S-scheme heterojunction mechanism. This work provides new ideas and breakthroughs for the design and construction of sulfide photocatalysts with excellent photocatalytic stability.