3D/2D Heterojunction Fabricated from RuS 2 Nanospheres Encapsulated in Polymeric Carbon Nitride Nanosheets for Selective Photocatalytic CO 2 Reduction to CO.

Micro/nanostructure control of heterostructures is still a challenge for achieving high efficiency and selectivity of photocatalytic CO 2 conversion. In this work, a new three-dimensiona/two-dimensional (3D/2D) heterostructure is fabricated by encapsulating RuS 2 nanospheres in the interlayer of mesoporous polymeric carbon nitride (PCN) nanosheets based on an in situ growth and polymerization strategy. The unique microstructure of the obtained 3D/2D RuS 2 /PCN heterojunction can effectively improve the transfer and separation efficiency of photogenerated charge carriers, reduce the mass transfer resistance of CO 2 toward active sites, and provide a confined reaction space, thus propelling the photocatalytic CO 2 reduction to CO with high selectivity. The CO yield over the optimal 5%-RuS 2 /PCN sample reaches 4.2 and 2.8 times as high as that of single PCN and RuS 2 within 4 h, respectively. Furthermore, the plausible charge transfer mechanism and CO 2 reduction path are revealed by time-dependent in situ Fourier transform infrared (FT-IR) spectra combined with photophysical, electrochemical, and photoelectrochemical techniques and density functional theory (DFT) calculations. This work develops the microstructural engineering design strategy of PCN-based heterojunctions for selective photocatalytic CO 2 fuel conversion.