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

Micro/nanostructure control of heterostructures is still a challenge for achieving high efficiency and selectivity of photocatalytic CO conversion. In this work, a new three-dimensiona/two-dimensional (3D/2D) heterostructure is fabricated by encapsulating RuS 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/PCN heterojunction can effectively improve the transfer and separation efficiency of photogenerated charge carriers, reduce the mass transfer resistance of CO toward active sites, and provide a confined reaction space, thus propelling the photocatalytic CO reduction to CO with high selectivity. The CO yield over the optimal 5%-RuS/PCN sample reaches 4.2 and 2.8 times as high as that of single PCN and RuS within 4 h, respectively. Furthermore, the plausible charge transfer mechanism and CO 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 fuel conversion.