N-CQDs act as electronic warehouse in N-CQDs/CdS regulate adsorption energy to promote photocatalytic selective oxidation of aromatic alcohols

The benzaldehyde (BAD) produced by the benzyl alcohol (BA) oxidation method is comprehensively applied to food and pharmaceutical fields. However, the selectivity and conversion of photocatalytic selective oxidation of BA in aqueous solution are still far from expectation. Herein, N-CQDs/CdS composites were synthesized by the in-situ precipitation method. N-CQDs served as an "Electronic Warehouse" to boost the separation efficiency of the carrier. The electron transferred from CdS to N-CQDs made electron on the N-CQDs surface enrich, which was conducive to the formation of superoxide radicals (·O 2 - ).·O 2 - and h + could efficiently oxidize BA to BAD. In addition, according to density functional theory (DFT), the adsorption energies of BA and BAD on N-CQDs/CdS were distinctly greater than that of CdS. BAD tended to desorb from the 7.5 N-CQDs/CdS surface, and BA preferred to adsorb on the CdS surface. However, BAD was difficult to desorb from the CdS surface, resulting in the poisoning of CdS. 7.5 N-CQDs/CdS exhibited the BA conversion of 60.4% and BAD selectivity of 99%, which was 2.2 times higher than that of original CdS. This work was expected to provide a theoretical basis for improving photocatalyst carrier separation efficiency and alcohol selective oxidation performance.