Enhanced visible-light photocatalytic hydrogen production activity of three-dimensional mesoporous p-CuS/n-CdS nanocrystal assemblies

Abstract

Transition metal sulfide nanoparticles currently attract enormous research attention because of their high photon-to-electron conversion efficiency, excellent electron conductivity and low cost. However, single-component metal sulfides suffer from low charge-carrier separation yield and poor chemical stability. Here, we report the synthesis of mesoporous structures of n-type CdS and p-type CuS nanocrystals and investigate their photocatalytic performance for the generation of hydrogen from water. X-ray diffraction, transmission electron microscopy and nitrogen physisorption data indicate that the resultant CuS/CdS heterostructures consist of a highly porous network (BET surface area ∼198–203 m² g⁻¹) of connected 5 nm-sized nanoparticles and contain uniform mesopores (ca. 6.4 nm in diameter) within the assembled structure. The nanoparticles are composed of CuS compounds which are in intimate contact with CdS nanocrystals, and these results are corroborated with energy-dispersive and X-ray photoelectron spectroscopy measurements. These CuS/CdS binary semiconductors can carry out photocatalytic reduction of water under visible light irradiation with a quantum efficiency up to ∼12.6% at a wavelength of 420 ± 10 nm. UV–vis/NIR, photoluminescence and electrochemical impedance spectroscopy studies show that the superior photocatalytic activity of the CuS/CdS nanoparticle networks mainly arises from a proper alignment of the band-edge positions of the materials, which suppress carrier recombination and permit efficient interfacial charge transport at the p-CuS/n-CdS junction region.