Hierarchical ternary layered double hydroxide/graphitic carbon nitride heterostructures as visible-light photocatalysts for efficient reduction of CO₂

The development and synthesis of high-efficient, stable, and cost-effective photocatalysts to reduce both world-wide energy and environmental issues are the most significant challenge in CO₂ reduction. Herein, we explore the photocatalytic performance over NiFeV layered double hydroxide (LDH) nanosheets, g-C₃N₄, and NiFeV-LDH/g-C₃N₄ heterostructures, which convert CO₂ into high value-added fuels, such as CO and CH₄. The 2D/2D hierarchical flower-like structure created an outstanding heterosystem with close interfaces and prominently exposed catalytic active sites to dramatically improve light-harvesting ability. The charge transfer among the individual components made the separation of photogenerated charge carriers easier and lessened their recombination rate, enhancing the photoreduction of CO₂. The ratio of g-C₃N₄ to NiFeV-LDH in term of weight had a significant impact on the photocatalytic activity of the NiFeV-LDH/g-C₃N₄ heterostructure. The photocatalyst generated the maximum yields of CH4 (15.2 µmolh⁻¹g⁻¹) when the weight ratio of g-C₃N₄ to NiFeV-LDHs was 15%, which was 4.04 times that of pure NiFeV-LDH. The yield of CO was 13.05 µmolh⁻¹g⁻¹, 3.15 times that of pure NiFeV-LDH. Furthermore, during cycling experimental runs, the optimized NiFeV-LDH/g-C3N4-15% heterostructure exhibited a remarkable photostability with no discernible change in the amounts of CO and CH₄ formation. The significantly improved photocatalytic performance towards CO₂ reduction was confirmed by the XPS and HRTEM analyses, which showed strong electronic interactions and promoted charge transfer between heterostructure components. The current study provides a feasible way to enhance the photocatalytic performance of LDH-based heterostructures and opens up new prospects for developing LDH-based photocatalysts towards CO₂ reduction. © 2022 Elsevier B.V.