Graphitic Carbon Nitride with Dopant Induced Charge Localization for Enhanced Photoreduction of CO₂ to CH₄

The photoreduction of CO₂ to hydrocarbon products has attracted much attention because it provides an avenue to directly synthesize value-added carbon-based fuels and feedstocks using solar energy. Among various photocatalysts, graphitic carbon nitride (g-C₃N₄) has emerged as an attractive metal-free visible-light photocatalyst due to its advantages of earth-abundance, nontoxicity, and stability. Unfortunately, its photocatalytic efficiency is seriously limited by charge carriers' ready recombination and their low reaction dynamics. Modifying the local electronic structure of g-C₃N₄ is predicted to be an efficient way to improve the charge transfer and reaction efficiency. Here, boron (B) is doped into the large cavity between adjacent tri-s-triazine units via coordination with two-coordinated N atoms. Theoretical calculations prove that the new electron excitation from N (2p _x , 2p _y ) to B (2p _x , 2p _y ) with the same orbital direction in B-doped g-C₃N₄ is much easier than N (2p _x , 2p _y ) to C 2p _z in pure g-C₃N₄, and improves the charge transfer and localization, and thus the reaction dynamics. Moreover, B atoms doping changes the adsorption of CO (intermediate), and can act as active sites for CH₄ production. As a result, the optimal sample of 1%B/g-C₃N₄ exhibits better selectivity for CH₄ with ≈32 times higher yield than that of pure g-C₃N₄.