Surface Sulfate Ion on CdS Catalyst Enhances Syngas Generation from Biopolyols

Photocatalytic biomass conversion represents an ideal way of generating syngas because of the sustainable use of biomass carbon and solar energy. However, the lack of efficient electron-proton transfer limits its efficiency. We here report an unprecedented method to simultaneously increase both the electron and proton transfer by creating surface sulfate ions on the CdS catalyst ([SO₄]/CdS). Surface sulfate ion [SO₄] is bifunctional, serving as the proton acceptor to promote proton transfer, and increasing the oxidation potential of the valence band to enhance electron transfer. [SO₄]/CdS produces a syngas mixture from glycerol without CO₂. Compared with pristine CdS, [SO₄]/CdS exhibits 9-fold higher CO generation rate (0.31 mmol g^-1 h^-1) and 4-fold higher H₂ generation (0.05 mmol g^-1 h^-1). A wide range of sugars, such as glucose, fructose, maltose, sucrose, xylose, lactose, insulin, and starch, were facilely converted into syngas. This study reports the pivotal effect of surface sulfate ion on electron-proton transfer in photocatalysis and provides a facile method for increasing photocatalytic efficiency.