Thermally assisted photocatalytic conversion of CO₂–H₂O to C₂H₄ over carbon doped In₂S₃ nanosheets

The development of an efficient photocatalyst for selective conversion of CO2 to ethylene (C2H4) is highly desirable. Here, carbon-doped In2S3 nanosheet-based spheres (denoted as C-In2S3) are reported to be highly efficient for thermally assisted photocatalytic conversion of CO2–H2O to C2H4 at 150 °C without any cocatalysts or sacrificial agents. The total consumed electron number (TCEN) for CO2 conversion over C-In2S3 can reach 472.7 μmol g−1 h−1. The selectivity and production rate of C2H4 over C-In2S3 are about 50% and 26.6 ± 4.1 μmol g−1 h−1, respectively, with a quantum efficiency of 13.3% at 420 nm. Meanwhile, no C2H4 can be detected over In2S3 without carbon doping. 13CO2 and D2O isotope labeling experiments confirm the carbon and hydrogen origins of C2H4. In situ experimental and theoretical studies reveal that carbon doping accelerates CO2 adsorption and activation, lowering the energy barrier to form CH*, the key intermediate for C2H4, thus leading to high selectivity.