Controllable photodeposition of nickel phosphide cocatalysts on cadmium sulfide nanosheets for enhanced photocatalytic hydrogen evolution performance

Abstract

Transition metal phosphides are efficient cocatalysts in photocatalytic water splitting processes, but these phosphides are usually synthesized through harsh and tedious processes, therefore, achieving a simple, controllable and in situ loading on the photocatalyst surface is especially valuable. In this paper, two-dimensional CdS nanosheets were prepared using a hydrothermal method, followed by in situ loading of nickel phosphide (NiP_x) nanoparticles on their surface by a photochemical reduction method, and NiP_x loading amounts could be adjusted just by the photodeposition time. The synthesized CdS–NiP_x was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometer, fluorescence spectroscopy and so on. CdS–NiP_x exhibited better photocatalytic performances than bare CdS, and the optimal hydrogen evolution rate of 28.7 mmol g⁻¹ h⁻¹ was realized for CdS–NiP_x with a photoreduction time of 20 min. The enhancement mechanism of their photocatalytic activity was estimated by comparing the photoluminescence spectra, electrochemical impedance spectra and transient photocurrent spectra of CdS–NiP_x and CdS, which indicated that photodeposited NiP_x could serve as excellent cocatalysts to efficiently suppress the recombination of electron–hole pairs photogenerated in CdS.