Electrostatic self-assembly of g-C3N4/AgInS2 heterostructures with electronic localization at sulfur site for enhanced CO2 photoreduction performance.

The efficiency of graphitic carbon nitride (g-C3N4) in photocatalytic reduction of carbon dioxide (CO2) is inhibited by the constrained CO2 chemisorption, insufficient light absorption and quick charge recombination. To address these problems, we successfully synthesized g-C3N4/AgInS2 (CN/AgInS2) heterostructured photocatalytic materials via an electrostatic self-assembly method. An intimate phase contact between CN and AgInS2 is formed, paving the way for the charge transfer and redistribution near the interface of the CN/AgInS2 heterostructures. Ex situ XPS investigations demonstrate a directional electron transfer from CN to AgInS2 within the CN/AgInS2 heterostructures, contributing to the establishment of electron-riched S(2+δ)- sites. The localized electrons on S(2+δ)- sites benefit the CO2 adsorption and activation, which is confirmed by density functional theory (DFT) simulations as well as CO2-temperature-programmed desorption (TPD) characterization. The charge transfer efficiency within CN/AgInS2 heterostructure is also promoted as revealed by PL spectra and photoelectrochemical measurements. Benefitting from the extended light absorption, efficient CO2 activation and augmented charge transfer rate, the resulting CN/AgInS2 heterostructures demonstrate enhanced CO production rate with the highest value of 121.08 μmol·h-1·g-1. Our research presents a new insight for modulating the active sites for CO2 reduction with high electron density through constructing heterojunction photocatalysts.