Layered double hydroxide for photocatalytic application toward CO₂ reduction and water splitting: Recent advances, synthesis, heterojunction formation, challenges, and future directions.

This article comprehensively reviews the synthesis, modification, and photocatalytic applications of layered double hydroxides (LDHs) for solar fuel production via water splitting and CO₂ reduction. It details various synthesis methods—including coprecipitation, hydrothermal, ion exchange, reconstruction, electrodeposition, separate nucleation and aging steps (SNAS), and layer-by-layer assembly—and discusses how these influence LDH structure, morphology, and photocatalytic properties. The review further examines strategies to enhance LDH performance, such as semiconducting and optical property tuning, morphological and defect engineering, component (cation/anion) adjustment, photothermal catalysis, and heterojunction engineering (including p–n, Schottky, type-I/II, Z-scheme, and S-scheme heterojunctions) to improve charge separation and light absorption. Recent advancements in pristine and composite LDH photocatalysts coupled with materials like TiO₂, g-C₃N₄, metals, metal oxides, sulfides, and MXenes are summarized, highlighting their efficacy in photocatalytic CO₂ conversion to fuels and water splitting for H₂ and O₂ generation. The article concludes that while LDHs show significant promise as efficient, tunable, and scalable photocatalysts, further research is needed to optimize synthesis, defect control, component tuning, and heterostructure design to achieve commercial viability.