Nb-O-C Charge Transfer Bridge in 2D/2D Nb2O5/g-C3N4 S-Scheme Heterojunction for Boosting Solar-Driven CO2 Reduction: In Situ Illuminated X-Ray Photoelectron Spectroscopy Investigation and Mechanism Insight

Although the construction of heterojunction photocatalysts is a promising way to achieve outstanding photocatalytic activities, a 2D heterojunction which possesses strong chemical bonding and appropriate interfacial contact toward efficient artificial photosynthesis is still a challenge. Herein, 2D/2D Nb2O5/g-C3N4 S-scheme heterojunction photocatalysts are successfully fabricated by a convenient in situ calcination route derived from niobic acid/urea precursor for the gas-solid CO2 reduction reaction. Under simulated solar irradiation, the total yield of C-1 products (CH4 and CO) obtained on the optimized sample NOCN-5 are 6.7 times and 5.3 times that over pristine Nb2O5 and g-C3N4 nanosheets, respectively, without sacrificial agent or cocatalysts. The enhanced performances of CO2 photoreduction might be attributed to the unique Nb-O-C chemical bonds induced charge transfer bridge, face-to-face contact, and the efficient S-scheme transfer path of photoinduced electron-hole pairs, which is confirmed by in situ illuminated X-ray photoelectron spectroscopy and density functional theory calculation. This work will provide a promising strategy for constructing S-scheme heterojunction systems for efficient artificial photosynthesis reactions toward carbon neutrality.

Automated summary

In this study, a 2D/2D Nb2O5/g-C3N4 S-scheme heterojunction photocatalyst was successfully fabricated for the photocatalytic CO2 reduction reaction. Under simulated solar irradiation, the optimized sample exhibited 6.7 times and 5.3 times higher total yield of C-1 products (CH4 and CO) compared to pristine Nb2O5 and g-C3N4 nanosheets, respectively, without sacrificial agent or cocatalysts. The improved performance of CO2 photoreduction can be attributed to the unique charge transfer bridge, face-to-face contact, and efficient S-scheme transfer path of photoinduced electron-hole pairs in the heterojunction.