Constructing Layered Double Hydroxide-Based Micro-Nano Reactors for Enhanced Nitrogen Photofixation

Efficient photofixation of N₂ in aqueous photocatalyst dispersions is hampered by the very low solubility and diffusion coefficient of N₂ in water. Herein, we designed and constructed 3D micro-nano reactors based on zinc-aluminum layered double hydroxide (3D-LDH) to overcome these challenges. Notably, the unique spatial architecture of the micro-nano reactors (containing vertical ZnAl-LDH arrays) visually captured by confocal laser scanning microscopy enriches the local concentration of small gas molecules during photocatalysis. The spillover kinetic analysis using oxygen as a probe molecule verified the enhanced diffusion of small gas molecules in the local vicinity of the 3D-LDH catalyst. Accordingly, 3D-LDH delivered superior photocatalytic activity for nitrogen photofixation compared to traditional LDH photocatalysts (2D-LDH and bulk-LDH). As a demonstration of the universality of this approach, 3D-BiOBr and 3D-TiO₂ equipped with micro-nano reactors were also prepared, demonstrating notably enhanced performance for photocatalytic H₂O₂ synthesis and aqueous dye degradation compared to their 2D counterparts. This work thus identifies a practicable strategy for enhancing the rates of photocatalytic reactions in aqueous media that utilize a gas-phase reactant.