Facile synthesis of few-layer g-C3N4 nanosheets anchored with cubic-phase CdS nanocrystals for high photocatalytic hydrogen generation activity

Abstract

Abstract g-C3N4 and CdS have attracted intense attention in the field of energy and environment research. Cubic-phase CdS possesses a smaller bandgap than that of hexagonal CdS but has seldom been used as photocatalytic material. This work focuses on the photocatalytic H2 generation of few-layer g-C3N4 nanosheets (CNS) anchored with cubic-phase CdS nanocrystals (CNS–CdS). The CNS–CdS composites were synthesized by depositing cubic-phase CdS on the surface of CNS in a sulfur-rich solution. Owing to the large specific surface area, rich active sites and strong synergy between cubic CdS and g-C3N4 nanosheets, the CNS–CdS showed the enhanced light absorption and separation of the photo-generated carriers, which endowed it with superior H2 generation activity and stability. The optimal average hydrogen production rate of the CNS–CdS photocatalyst reached to 2.24 mmol∙h−1·g−1 under irradiation of AM 1.5G, which was 3.5 and 3.3 times of that of cubic CdS and few-layer g-C3N4 nanosheets, respectively. The best apparent quantum efficiency at 475 nm reached up to 13.83%, and the maximum conversion efficiency of incident photon-to-current is 59.6% in the wavelength range of 350–700 nm. The excellent stability of the as-prepared CNS–CdS was also proven by the cyclic run. The results suggest the replacement of hexagonal CdS with cubic CdS result in energy-saving, performance-stable and high-efficient photocatalytic materials.