Enhanced CO 2 photoreduction to CH 4 via *COOH and *CHO intermediates stabilization by synergistic effect of implanted P and S vacancy in thin-film SnS 2

Reduction of CO 2 to value-added hydrocarbons through artificial photosynthesis is one of the way to address the energy crisis and climate change issues. It is known that lowering the activation energy of CO 2 molecules on the photocatalyst surface and key intermediates is crucial in photocatalytic CO 2 reduction. Herein, we present phosphorus -implanted 20-nm SnS 2 continuous thin film with sulfur vacancies ( i.e. , S V -SnS 2 :P where P substitutes on S sites). The fabrication process involves thermal evaporation, post-sulfurization, and ion implantation. Our gas -phase photocatalytic experiments show an enhanced and selective CO 2 photoreduction to CH 4 with a yield of 0.13 mu mol cm -2 and selectivity of 92 % under solar -light irradiation for 4 h over an optimal -4.5 % P and -16 % S V . Experimental observations, conducted through X-ray absorption near edge, in situ near ambient pressure Xray photoelectron, and in situ Fourier transform infrared spectroscopies, along with first -principle density functional theory calculations. Results reveal that P dopant is significantly affected by nearby S V via local charge density transfer from P to the nearest Sn and next -nearest S neighbor atoms, consequently, leads to the stabilization of *COOH and *CHO intermediates, where asterisks stand for P as the active site. Our results demonstrate how active site modulation, without using precious co -catalysts, plays a crucial role in intermediate stabilization in a wireless photocatalysis process.