Potassium-Doped g‑C₃N₄ Achieving Efficient Visible-Light-Driven CO₂ Reduction

Abstract

The\nvisible-light-driven CO₂ reduction efficiency is\nlargely restrained by the negative photoabsorption and high recombination\nrate of electron–hole pairs. It is an effective method to increase\nthe efficiency of CO₂ photoreduction by doping alkali metal\nelements to engineer the electronic properties of the catalyst. Here,\nwe report a new study on the potassium-doped g-C₃N₄ (K-CN) being used for CO₂ reduction irradiated\nby visible light. DFT calculations and XPS tests show that the potassium\ndoping is interlayer doping, changing the electronic structure of\ng-C₃N₄. The higher <i>I</i>_D/<i>I</i>_G value indicates more structural distortion\nand defects caused by K doping. K-CNs have enhanced visible-light\nabsorption, and PL spectra demonstrate that the introduction of potassium\nadvances the separation and transmission of photoexcited charge carriers,\nfurther confirmed by transient photocurrent response experiment. Under\nvisible light, K-CN-7 achieved efficient CO₂ reduction\nwithout any noble metal as a cocatalyst, with CO formation rates of\n8.7 μmol g^–1 h^–1, which\nis 25 times that of ordinary g-C₃N₄. Our work\nfurther validates the importance of inhibiting e^–/h⁺ recombination in improving solar energy conversion\nefficiency while also bringing hope for efficient solar fuel production\nusing g-C₃N₄.