Hierarchically CuInS 2 Nanosheet‐Constructed Nanowire Arrays for Photoelectrochemical Water Splitting

This paper reports a facile self‐templated method to prepare hierarchically CuInS 2 nanosheet‐constructed nanowire arrays (NCNAs) using Cu 2 S nanowires arrays (NWAs) as the template. The as‐synthesized CuInS 2 nanosheets show ultrathin thickness of ≈1.2 nm, corresponding to the thickness of 4 atomically thick CuInS 2 slab along the [221] direction. The CuInS 2 nanosheet‐constructed nanowires exhibit diameters of several hundred nanometers and lengths of several micrometers. The novel exchange‐peeling growth mechanism suggests that the In 3+ insertion proceeds preferentially along the (−204) facets of pristine Cu 2 S nanowires, and the distortions and strains sourced from lattice mismatch cause the longitudinal expansion along the c ‐axis and the splitting of S−S bond during the formation of 3D CuInS 2 NCNAs. It is also found that relative higher In 3+ concentration is beneficial to this process. Compared to 0.15 mA cm −2 of the pristine Cu 2 S NWAs, the CuInS 2 photocathodes show an enhanced photocurrent of 0.49 mA cm −2 at −0.1 V versus the reversible hydrogen electrode, and the photocurrent can be further increased to 1.14 mA cm −2 via decoration with CdS quantum dots. The density functional theory calculation results confirm that the ultrathin CuInS 2 nanosheets favor for higher carrier mobility, thus ensure promoted photoelectrochemical efficiency.