Insights into the role of C-S-C bond in C3N5 for photocatalytic NO deep oxidation: Experimental and DFT exploration

Non-stoichiometric polymer carbon nitride of C3N5 is becoming an important visible-light-type catalyst due to the narrow bandgap, non-toxicity, and thermal stability. Here, we report a sulfur doping strategy for upgrading the photogenerated carriers’ dynamics of C3N5. Studies on the transient diffuse reflectance spectra prove that the lifetime of photogenerated carriers of sulfur-doped C3N5 (S-C3N5) increases 61.6 %. The widened visible-light responsive range and enhanced structural defects are also confirmed by UV–vis DRS and ESR characterizations. DFT calculations also verify the better NO adsorption and activation as well as give an insight into the mechanism of NO conversion from the molecule level. Such unique properties endow S-C3N5 with a 4.9- and 5.1-fold increase in photocatalytic NO removal efficiency and rate respectively compared to C3N5. In-situ DRIFTS tests demonstrate the excellent NO deep-oxidation capability of S-C3N5. Ten-cycle NO removal experiments prove its reusability and durability.