S-scheme heterojunction Cu-porphyrin/TiO2 nanosheets with highly efficient photocatalytic reduction of CO2 in ambient air

Directly capturing CO2 in ambient air and converting it into value-added fuels using photocatalysis is a potentially valuable technology. In this study, Cu-porphyrin (tetrakis-carboxyphenyl porphyrin copper, CuTCPP) was innovatively anchored on the surface of TiO2 (titanium dioxide) nanosheets to form an S-scheme heterojunction. Based on this, a photocatalytic reaction system for stably converting CO2 in ambient air into value-added fuels at the gas–solid interface was constructed without addition of sacrificial agents and alkaline liquids. Under the illumination of visible light and sunlight, the evolution rate of CO is 56 μmol·g−1·h−1 and 73 μmol·g−1·h−1, respectively, with a potential CO2 conversion rate of 35.8 % and 50.4 %. The enhanced of photocatalytic performance is attributed to the introduction of CuTCPP, which provides additional active sites, significantly improves capture capacity of CO2 and the utilization of electrons. Additionally, the formation of S-scheme heterojunction expands the redox range and improves the separation efficiency of photo-generated charges.