Enhanced electron–hole separation in SnS2/Au/g-C3N4 embedded structure for efficient CO2 photoreduction

Energy band location and charge separation mechanism of SnS2/Au/g-C3N4 system during photoreduction under sunlight irradiation. [Display omitted] •The catalyst is prepared by facile thermal treatment and chemical deposition method.•The SnS2/Au/g-C3N4 composites show a superior optical adsorption under UV–vis light.•The Au nanoparticle and the Z-type scheme jointly improve the separation of carrier.•The SnS2/3ml-Au/g-C3N4 displays the best photoreduction activity and durability. The use of semiconductor photocatalytic reduction technology has higher efficiency and lower energy consumption for CO2 reduction, but its existence of some mismatched energy band positions and relatively slow charge-hole separation greatly limits its practical application. In this paper, a SnS2/Au/g-C3N4 embedded structure model with carbon and nitrogen hybridization is proposed to gain an in-depth understanding of the role of hybridization and precious metal modification in photocatalysis. Carriers were investigated from the perspective of kinetics through photocurrent, LSV curve, and FL spectroscopy. After modification of Au nanoparticles, the photo-excited electrons showed a slower decay process, indicating that the separation of carriers was enhanced, which was further confirmed by impedance and PL spectroscopy. SEM, AFM and TEM analysis confirmed that the 2D face-to-face SnS2/Au/g-C3N4 embedded structure was successfully prepared and the Au nanoparticles were evenly distributed. Au nanoparticles not only act as a bridge for electron transport in 2D semiconductor materials to accelerate electron transport, but generate more excited electrons by themselves under the radiation of sunlight, which effectively improves the separation efficiency of electron-hole pairs and enhances the photocatalyst activity. DFT calculations show that the Z-type mechanism and the intercalated energy level of the SnS2/Au/g-C3N4 embedded structure expand the light absorption and improve the carrier separation efficiency. As expected, the photocatalyst activity with CO and CH4 the evolution rate of up 93.81 µmol·g−1·h−1 and 74.98 µmol·g−1·h−1 under visible light irradiation, respectively, while the photocatalytic activity is negligible loss after 30 h photoreduction. This work reveals the role of embedded structure and precious metal modification in the separation and transmission of electron-hole, opening up new perspective for achieving high-efficiency solar CO2 reduction performance.