Accelerating Electron-Transfer and Tuning Product Selectivity Through Surficial Vacancy Engineering on CZTS/CdS for Photoelectrochemical CO2 Reduction

Shujie Zhou; Kaiwen Sun; Jialiang Huang; Xinxin Lu; Bingqiao Xie; Doudou Zhang; Judy N Hart; Cui Ying Toe; Xiaojing Hao; Rose Amal

doi:10.1002/smll.202100496

Accelerating Electron-Transfer and Tuning Product Selectivity Through Surficial Vacancy Engineering on CZTS/CdS for Photoelectrochemical CO₂ Reduction

Small. 2021 Aug;17(31):e2100496. doi: 10.1002/smll.202100496. Epub 2021 Jun 25.

Authors

Affiliations

¹ School of Chemical Engineering, UNSW Sydney, Sydney, NSW, 2052, Australia.
² School of Photovoltaic and Renewable Energy Engineering, UNSW Sydney, Sydney, NSW, 2052, Australia.
³ Research School of Electrical, Energy and Materials Engineering, The Australian National University, Canberra, ACT, 2601, Australia.
⁴ School of Materials Science and Engineering, UNSW Sydney, Sydney, NSW, 2052, Australia.

PMID: 34173332
DOI: 10.1002/smll.202100496

Abstract

Copper-based chalcogenides have been considered as potential photocathode materials for photoelectrochemical (PEC) CO₂ reduction due to their excellent photovoltaic performance and favorable conduction band alignment with the CO₂ reduction potential. However, they suffer from low PEC efficiency due to the sluggish charge transfer kinetics and poor selectivity, resulting from random CO₂ reduction reaction pathways. Herein, a facile heat treatment (HT) of a Cu₂ ZnSnS₄ (CZTS)/CdS photocathode is demonstrated to enable significant improvement in the photocurrent density (-0.75 mA cm^-2 at -0.6 V vs RHE), tripling that of pristine CZTS, as a result of the enhanced charge transfer and promoted band alignment originating from the elemental inter-diffusion at the CZTS/CdS interface. In addition, rationally regulated CO₂ reduction selectivity toward CO or alcohols can be obtained by tailoring the surficial sulfur vacancies by HT in different atmospheres (air and nitrogen). Sulfur vacancies replenished by O-doping is shown to favor CO adsorption and the CC coupling pathway, and thereby produce methanol and ethanol, whilst the CdS surface with more S vacancies promotes CO desorption capability with higher selectivity toward CO. The strategy in this work rationalizes the interface charge transfer optimization and surface vacancy engineering simultaneously, providing a new insight into PEC CO₂ reduction photocathode design.

Keywords: CZTS/CdS; band alignment; fuel product selectivity; heat treatment; photoelectrochemical CO 2 reduction; sulfur vacancies.

Abstract

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