Enhancing g‐C ₃ N ₄ Photocatalytic Activity: K‐Doping and CuO Heterojunction for Selective CO ₂ Conversion to CH ₄

ABSTRACT Photocatalytic CO 2 reduction to CH 4 has attracted notable focus because of its capacity to convert CO 2 into high‐value hydrocarbon fuels. Among the different photocatalysts, g‐C 3 N 4 (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‐C 3 N 4 framework to improve its crystallinity, which was followed by coupling with CuO to form a CuO/K‐g‐C 3 N 4 heterostructure to improve charge separation. The CuO/K‐g‐C 3 N 4 photocatalysts achieved excellent CO 2 photoreduction performance, yielding 41.21 μmol/g/h CH 4 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 CO 2 adsorption. This work discloses a g‐C 3 N 4 ‐derived photocatalyst design as well as stresses the capability of CuO/K‐g‐C 3 N 4 as a photoactive catalyst for elevated CH 4 selectivity, contributing to renewable energy and environmental protection.