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Environmentally friendly Cu2ZnSnS4-based photocathode modified with a ZnS protection layer for efficient solar water splitting

Author:
Wang, Kang, Huang, Dingwang, Yu, Le, Gu, Huaimin, Ikeda, Shigeru, Jiang, Feng
Source:
Journal of colloid and interface science 2019 v.536 pp. 9-16
ISSN:
0021-9797
Subject:
cathodes, copper zinc tin sulfide, electrolytes, electron transfer, glass, hydrogen, photocatalysis, pyrolysis, zinc sulfide
Abstract:
High-quality Cu2ZnSnS4 (CZTS) thin films prepared by spray pyrolysis on a Mo-coated glass substrate were used for solar water splitting in this study. Modification of a CdS layer under CZTS improved the photocatalysis efficiency by forming a pn junction between CdS and CZTS, effectively separating the photoexcited carriers without recombination. However, the photocorrosive nature of CdS induces poor stability of the CdS/CZTS photocathode. Surface protection of a CdS-covered CZTS photocathode by a ZnS layer resulted in efficient photoelectrochemical water splitting with a maximum half-cell solar to hydrogen (HC-STH) efficiency of 2.1% and without showing appreciable degradation. The ZnS layer acts as a mediator for efficient electron transport to Pt deposits and as a protective layer, preventing contact between the CdS layer and the outer electrolyte solution.