Plasmon-enhanced photocatalytic cumulative effect on 2D semiconductor heterojunctions towards highly-efficient visible-light-driven solar-to-fuels conversion

Abstract

The photocatalytic activity of a semiconductor is heavily influenced by its photocatalytic cumulative effect on the four consecutive photo-physiochemical processes, including (I) light harvesting, (II) charge separation, (III) charge migration, and (IV) charge utilization. However, it is still a tremendous challenge to enhance the photocatalytic cumulative effect by simultaneously sensitizing the total above I-IV processes of the semiconductor. Herein, we synthesized the well-designed plasmonic Au@Pt/CdS/C3N4 heterostructure through assembling Pt/CdS-selective-coated Au nanocubes onto the two dimensional (2D) ultrathin C3N4 nanosheets (NSs). We have also demonstrated that selectively coating CdS nanoparticle-clusters (NPCs) and Pt nanoparticles (NPs) onto the surfaces and edges of Au NCs could boost the II and III processes of the formed Au@Pt/CdS NCs based on the resonance energy transfer (RET) and “hot electron” transfer (HET) behaviors, respectively, due to the localized surface plasmon resonance (LSPR) of Au NCs. The assembly of the Au@Pt/CdS NCs onto the C3N4 NSs formed lots of 2D Au/CdS/C3N4 interface, where the Au-LSPR not only boosted the I process at the “type II” heterojunction regions of CdS/C3N4, but also improved the II process of C3N4 NSs via the local electromagnetic field enhancement (LEFE). Furthermore, the quasi-2D porous structure of CdS NPCs increased the surface active-sites at the 2D CdS/C3N4 interface, therefore enhancing the IV process. As such, when normalizing the effective active area as the Au@Pt/CdS/C3N4 hetero-interface region, the plasmonic heterostructure exhibited the ∼ 17.2-fold and ∼ 14.3-fold enhancements on the photocatalytic H2 evolution and CO2 reduction as compared to the CdS/C3N4 heterojunction, respectively.