Flower-like microspheres Z-scheme Bi2Sn2O7/NiAl-LDH heterojunction for boosting photocatalytic CO2 reduction under visible light.

Fabrication of efficient photocatalysts with great visible light utilization ability, rapid carriers' separation, and suitable redox potential is essential for improving photocatalytic CO2 reduction. Herein, flower-like microspheres Bi2Sn2O7/NiAl-layered double hydroxide (BSO/LDH) heterojunctions were prepared by hydrothermal process for CO2 reduction. The Bi2Sn2O7 nanoparticles were dispersed on NiAl-LDH nanosheets, with tight contact interface, which facilitated charges transfer and exposing more catalytic active sites. Results of photochemical deposition of metal/metal oxide demonstrated that interfacial charges transfer of the BSO/LDH followed Z-scheme mechanism, endowing more desired redox potential and more efficient carriers separation. The 30%-BSO/LDH showed the highest CO and CH4 yields of 37.91 and 1.18 µmol g-1 h-1 under visible light irradiation, 3.4 and 2.0 times higher than those from the NiAl-LDH, respectively. The main intermediates during CO2 reduction were carboxylate (COOH*) and aldehyde group (CHO*), and CO2 reduction pathways and mechanism were proposed accordingly. This study provided referential strategy for designing efficient heterojunction photocatalysts for CO2 conversion.