Co nanoparticles modified phase junction CdS for photoredox synthesis of hydrobenzoin and hydrogen evolution

Coupling photocatalytic H2 production with organic synthesis attracts immense attention in the field of energy research through collecting the sustainable green energy and high value-added products. Although tremendous progress has been made towards devoting to the oxidation of benzyl alcohol, only very limited study can meet high selectivity of the C–C coupled products during the process of H2 evolution. Herein, the phase junction CdS (HC-CdS2) consisting of hexagonal CdS (H-CdS) with co-exposed facets of (001) and (101) and cubic CdS (C-CdS) was fabricated by fine tuning the proportion of cadmium and sulfur sources for photocatalytic H2 production and selective benzyl alcohol oxidation. The HC-CdS2 is able to maintain a robust H2 evolution rate of 11 mmol g−1 by loading cobalt as cocatalyst, which is 4.7 and 34 times higher than those for C-CdS/Co and HC-CdS2, respectively. Especially, the selectivity of hydrobenzoin elevated from 12% to 97% after loading Co on HC-CdS2 after light irradiation for 9 h. EPR and in situ DRIFTS tests indicated that the hydrogen atom from the C–H bond of benzyl alcohol was abstracted to form ·C7H8O free radical. Subsequently, the ·C7H8O free radical coupling yield hydrobenzoin as the final C–C coupling product by ameliorating charge separation resulted from the internal electric fields of facet junction and phase junction CdS and Schottky junction between CdS and Co. The strategy can be further extended to various aromatic alcohols and provide a reference for highly selective synthesis of high-added value chemicals coupled with H2 evolution.