Self-assembled g-C3N4/ZnO quantum dots Z-scheme heterojunction for effective photocatalytic methane oxidation to C1 oxygenates under mild conditions

Direct photocatalytic methane conversion into high-value liquid oxygenates has garnered significant research interest under mild conditions, yet a critical challenge is to obtain an excellent formaldehyde yield rate and selectivity only using H 2 O as the oxidant. Herein, a 2D g-C 3 N 4 nanosheet/ 0D ZnO quantum dots (ZCN) Z -scheme heterojunction was established by the self-assembly strategy to acquire an outstanding C1 liquid oxygenates (methanol and formaldehyde) with productivity of 908.13 μmol g cat −1  h −1 under ambient temperature and pressure without extra oxidant. Notably, the HCHO yield rate could be reached to 706.32 μmol g cat −1  h −1 with a selectivity of 69 %. The confinement effect of ZnO quantum dots (ZnO QDs) broadens the bandgap to some extent, making the catalyst possess a strong oxidation potential that could oxidize H 2 O to generate enough hydroxyl radical ( · OH) for activating CH 4 . Meanwhile, the ZCN Z -scheme heterostructure improves the migration and transport efficiency of photoexcitons but also enhances the activation and adsorption of CH 4. In situ experiments verify that the ZCN heterostructure accelerates the generation of methyl radical ( · CH 3 ) and · OH. This work paves a new way toward rationally constructing photocatalysts for CH 4 conversion into desirable chemical products under ambient conditions.