Nickel selenide/g-C₃N₄ heterojunction photocatalyst promotes CC coupling for photocatalytic CO₂ reduction to ethane

Photocatalytic CO₂ reduction to generate high value-added and renewable chemicals is of great potential in facilitating the realization of closed-loop and carbon-neutral hydrogen economy. Stabilizing and accelerating the formation of COCO* intermediate is crucial to achieve high-selectivity ethane production. Herein, a novel 3D/2D NiSe₂/g-C₃N₄ heterostructure that mesoscale hedgehog nickel selenide (NiSe₂) grown on the ultrathin g-C₃N₄ nanosheets were synthesized via a successively high temperature calcination process and in-situ thermal injection method for the first time. The optimum 2.7 % NiSe₂/g-C₃N₄ heterostructure achieved moderate C₂H₆ generation rate of 46.1 μmol·g^-1·h^-1 and selectivity of 97.5 % without any additional photosensitizers and sacrificial agents under light illumination. Based on the results of the theoretical calculations and experiments, the improvement of photocatalytic CO₂ to C₂H₆ production and selectivity should be ascribed to the increased visible light absorption ability, unique 3D/2D heterostructures with promoted adsorption of CO₂ molecules on the Ni active sites, the type II heterojunction with improved charge transfer dynamics and lowered interfacial transfer resistance, as well as the formation of COCO* key intermediate. This work provides an inspiration to construct efficient photocatalysts for the direct transformation of CO₂ to multicarbon products (C₂₊).