Enhancing g-C₃N₄ Photocatalytic Activity: K-Doping and CuO Heterojunction for Selective CO₂ Conversion to CH₄

Photocatalytic CO₂ reduction to CH₄ has attracted notable focus because of its capacity to convert CO₂ into high-value hydrocarbon fuels. Among the different photocatalysts, g-C₃N₄ (graphitic carbon nitride) has emerged as an attractive candidate due to its stability, nontoxicity, and facile synthesis. However, its poor crystallinity and inefficient charge separation severely limit its photocatalytic efficiency. Herein, K⁺ ions were introduced into the g-C₃N₄ framework to improve its crystallinity, which was followed by coupling with CuO to form a CuO/K-g-C₃N₄ heterostructure to improve charge separation. The CuO/K-g-C₃N₄ photocatalysts achieved excellent CO₂ photoreduction performance, yielding 41.21 μmol/g/h CH₄ with 93.03% selectivity upon visible-light illumination. The augmented conversion ability was mainly due to the synergistic effects of better crystallinity, light arrestation, exciton dissociation, charge separation, and CO₂ adsorption. This work discloses a g-C₃N₄-derived photocatalyst design as well as stresses the capability of CuO/K-g-C₃N₄ as a photoactive catalyst for elevated CH₄ selectivity, contributing to renewable energy and environmental protection.