Non-Metal Sulfur Doping of Indium Hydroxide Nanocube for Selectively Photocatalytic Reduction of CO2 to CH4: A "One Stone Three Birds" Strategy

Photocatalytic CO2 reduction is considered as a promising strategy for CO2 utilization and producing renewable energy, however, it remains challenge in the improvement of photocatalytic performance for wide-band-gap photocatalyst with controllable product selectivity. Herein, the sulfur-doped In(OH)(3) (In(OH)(x)S-y-z) nanocubes are developed for selective photocatalytic reduction of CO2 to CH4 under simulated light irradiation. The CH4 yield of the optimal In(OH)(x)S-y-1.0 can be enhanced up to 39 times and the CH4 selectivity can be regulated as high as 80.75% compared to that of pristine In(OH)(3). The substitution of sulfur atoms for hydroxyl groups in In(OH)(3) enhances the visible light absorption capability, and further improves the hydrophilicity behavior, which promotes the H2O dissociation into protons (H*) and accelerates the dynamic proton-feeding CO2 hydrogenation. In situ DRIFTs and DFT calculation confirm that the non-metal sulfur sites significantly weaken the over-potential of the H2O oxidation and prevent the formation of center dot OH radicals, enabling the stabilization of *CHO intermediates and thus facilitating CH4 production. This work highlights the promotion effect of the non-metal doping engineering on wide-band-gap photocatalysts for tailoring the product selectivity in photocatalytic CO2 reduction.