Hierarchical metal–semiconductor–graphene ternary heteronanostructures for plasmon-enhanced wide-range visible-light photocatalysis

Abstract

Design of heteronanostructures with controlled topologies and configurations is receiving ever-increasing attention for developing practical photocatalytic and photoelectrochemical systems. Herein, we present a promising solar energy conversion platform constructed using the intimate contact of a plasmonic metal (octahedral Au nanocrystals), semiconductor (TiO₂), and graphene with a well-defined configuration. The shell engineering of Au nanocrystals with TiO₂ and graphene through sequential sol–gel, self-assembly, and post-calcination processes could allow the generation of graphene-encapsulated (octahedral Au nanocrystals)@(anatase TiO₂) core–shell nanostructures. The prepared ternary heteronanostructures exhibited superior photocatalytic hydrogen evolution activity over their binary counterparts, single-component catalysts, and physical mixtures of the constituents under visible-light irradiation (λ > 400 nm). Furthermore, they effectively utilized the red-light region for photocatalytic reactions. Detailed mechanism studies on the photocatalysis revealed that the prominent photocatalytic performance of the heteronanostructures can be attributed to the transfer of plasmon-induced hot electrons from Au nanocrystals to TiO₂ and the subsequent migration of the photogenerated electrons to graphene, which could be facilitated by the intimate contact between the constituent materials. This study can provide a new insight into devising heteronanostructures for efficient light harvesting.