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-C3N4 hybrids were successfully fabricated by a simple solvothermal method and applied for the first time to the photocatalytic reduction of CO2. Remarkably, the composites exhibited excellent CO2 conversion efficiencies in the presence of H2O under visible light irradiation compared to unmodified g-C3N4, especially for the production of CH4. The optimum photocatalyst 30-Bi/g-C3N4 presented the best production of CO and CH4, approximately 3 times and 9 times as high as those of unmodified g-C3N4, 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-C3N(4) and Bi metal and the solvothermal process, co-contributed for the enhanced CO2 conversion; A more important finding was that the surprising improvement of CH4 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 CO2 photocatalytic conversion process was also investigated by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) spectroscopy and we found that HCO3- and CO2- were active intermediates over 30-Bi/g-Co3No4 and Bi doping could promote the activation of CO2. In summary, this work presented hollow-structured Bi decorated gC(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 CO2 photocatalytic reduction processes.