Insight into the enhanced CO2 photocatalytic reduction performance over hollow-structured Bi-decorated g-C3N4 nanohybrid under visible-light irradiation

In this study, hollow-structured Bi decorated g-C 3 N 4 hybrids were successfully fabricated by a simple solvothermal method and applied for the first time to the photocatalytic reduction of CO 2 . Remarkably, the composites exhibited excellent CO 2 conversion efficiencies in the presence of H 2 O under visible light irradiation compared to unmodified g-C 3 N 4 , especially for the production of CH 4 . The optimum photocatalyst 30-Bi/g-C 3 N 4 presented the best production of CO and CH 4 , approximately 3 times and 9 times as high as those of unmodified g-C 3 N 4 , respectively. A series of characterizations were conducted to explore the essence behind such an enhancement; we found that enhanced light harvesting, quick separation of photoinduced carriers and more negative conduction band, due to the formation of a Schottky junction between g-C 3 N 4 and Bi metal and the solvothermal process, co-contributed for the enhanced CO 2 conversion; A more important finding was that the surprising improvement of CH 4 yield stem primarily from the introduction of the hollow-structured Bi, which enabled the accumulation of electrons on its surface exhibiting the metal-like property. The CO 2 photocatalytic conversion process was also investigated by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) spectroscopy and we found that HCO 3 − and CO 2 − were active intermediates over 30-Bi/g-C 3 N 4 and Bi doping could promote the activation of CO 2 . In summary, this work presented hollow-structured Bi decorated g-C 3 N 4 composites as new materials for energy applications, proving once more the meta-like nature of bismuth, and laying the groundwork for the utilization of Bi in CO 2 photocatalytic reduction processes.