A Density Functional Theory Study of the Cu<sub>2</sub>ZnSnS<sub>4</sub> Monolayer as a Photo-electrointegrated Catalyst for Water Splitting and Hydrogen Evolution
Ruifen Zhang, Xin Wen, Fen Xu, Qiubo Zhang, Lixian Sun
Abstract
Solar water splitting by photo-electrocatalysts is a promising route for efficiently producing hydrogen with a low cost. A general electrocatalyst and photocatalyst integrated system is challenging due to its multiple interfaces in heterogeneous junctions. In this work, the geometric, electronic, and photo-electrocatalytic properties of a Cu2ZnSnS4 monolayer (CZTS ML) were studied via a DFT method. Compared to its bulk counterpart, CZTS ML shows a larger band gap, more suitable band positions for overall water splitting, and lower overpotentials of HER and OER. Interestingly, the sulfur atoms on the basal plane of CZTS ML show a near-ideal free energy of adsorbed H (ΔGH ∼0.005 eV), which is more thermal-neutral than those of MoS2 and Pt. This work highlights the great potential of CZTS ML as an efficient overall water splitting photocatalyst and a low-cost effective HER electrocatalyst simultaneously.