Integrating photogenerated charge carriers for hydrogen production on noble-metal free dual-photocatalyst under visible light

Simultaneous using photogenerated electrons and holes in one reaction to produce H 2 and value-added organic intermediates hold great promise for the green synthesis of chemicals and clean energy. Herein, we designed an efficient, noble-metal free and dual-photocatalyst Ni/Zn 3 In 2 S 6 for simultaneous aldehydes synthesis and H 2 production under visible light irradiation. Due to the reasonable band structure of Zn 3 In 2 S 6 and the Schottky barrier established between Zn 3 In 2 S 6 and Ni, the photogenerated electrons and holes with suitable redox potentials can be spatially separated and efficiently transferred. Thereby, alcohols can be highly selective oxidized into corresponding aldehydes or carbonyl compounds at Zn 3 In 2 S 6 by the holes, and the released protons can be rapidly reduced into H 2 at Ni by the electrons. The H 2 evolution of the optimal Ni/Zn 3 In 2 S 6 can reach up to 277.2 μmol h −1 , which is about 6.5 and 5.3 times as high as that of the pristine Zn 3 In 2 S 6 and the Pt/Zn 3 In 2 S 6 , respectively. Ni/Zn 3 In 2 S 6 also shows the stability and general applicability for other aromatic and non-aromatic alcohols. Compared with NiS x , NiO x and Ni 2+ cocatalysts , the metallic state of Ni is the key to achieving these photoredox reactions for effective utilization of photoexcited holes and electrons in one reaction system. During the photoredox reactions, two protons derived from O –H and Cα-H are abstracted from alcohols and then reduced into H 2 by the photogenerated electrons. At the same time, alcohols are oxidized into aldehydes or carbonyl compounds by the photogenerated holes.