Cu–Ni core–shell bimetallic cocatalyst decorated polymeric carbon nitride for highly efficient and selective methane production from photocatalytic CO₂ reduction

The development of non-noble bimetallic cocatalysts for the efficient and selective CO₂ photoreduction is extremely desirable yet challenging. Herein, we rationally synthesized a series of non-noble Cu–Ni bimetallic cocatalysts by varying the Cu and Ni molar ratios, and then, we decorated these cocatalysts on polymeric carbon nitride (CN) for photocatalytic CO₂ reduction. Elemental distribution maps demonstrated that the Cu–Ni-11 bimetallic cocatalyst with a Cu:Ni molar ratio of 1:1 has a perfect core–shell configuration. Notably, this Cu–Ni-11 core–shell cocatalyst-decorated CN (Cu–Ni-11@CN) exhibited remarkable CO₂ photoreduction activity for selective CH₄ production, outperforming bare CN, Cu@CN, Ni@CN, and Cu–Ni-13@CN and Cu–Ni-31@CN catalysts with different metal proportions. Additionally, the Cu–Ni-11@CN catalyst was remarkably stable and durable over multiple test runs. The remarkable CO₂ conversion activity and stability of the developed catalyst are predominantly due to the synergistic effect of the Cu–Ni-11 core–shell cocatalyst and CN, which affords significantly improved optical absorption, CO₂ adsorption, and photoexcited charge separation. Therefore, the study results elucidate the rational design and development of non-noble bimetallic cocatalysts for photocatalytic CO₂ conversion.