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

Abstract

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 µmol h−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 µmol h−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.