Enhanced photoelectrochemical performance of NiS-modified TiO₂ nanorods with a surface charge accumulation facet

Photoelectrochemical (PEC) water splitting for hydrogen production technology is considered as one of the most promising solutions to energy shortage and environmental remediation. TiO₂/NiS nanorod arrays were successfully prepared using hydrothermal deposition followed by the successive ionic layer adsorption and reaction (SILAR) method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and photoluminescence (PL) spectra characterization studies indicate the successful deposition of NiS on TiO₂ NRs. The NiS deposition on TiO₂ was optimized by controlling the impregnation cycle. The optimal sample exhibits a photocurrent density of 1.16 mA cm^-2 at 0.6 V vs. Ag/AgCl, which is a 1.9-fold enhancement over that of pristine TiO₂ nanorod arrays. The enhanced photoelectrochemical performance can be attributed to two aspects. On the one hand, the (101) crystal plane of rutile TiO₂ is the facet where photogenerated holes accumulate and is an efficient active plane for the oxygen evolution reaction; on the other hand, NiS is a narrow band gap semiconductor, and its deposition on TiO₂ nanorods can further promote the separation and transport of photogenerated charge carriers.