In Situ Growth of Perovskite on 2D Hydrothermal Carbonation Carbon for Photocatalytic Reduction of Nitrate to Ammonia

Photocatalytic ammonia synthesis from waste nitrate provides a green strategy for water treatment, which holds great significance for the global water cycle. However, there is still a lack of highly efficient catalysts to meet the high conversion and selectivity. Herein, a nanostructured photocatalyst was prepared by assembling perovskite (LaFeO3) on hydrothermal carbonation carbon (HTCC) via a facile microwave hydrothermal method, which was employed to reduce nitrate to ammonia. The two-dimensional HTCC nanosheet had a large specific surface area and abundant surface functional groups, and Fe/La salt participated in the surface modification of HTCC, promoting the exposure of oxygen-containing functional groups and aromatic structure, which was favorable for the nitrate adsorption. Furthermore, the HTCC constructed a p–n heterojunction with LaFeO3, which improved the photocatalytic activity attributed to the fast separation of photogenerated electron holes. At the optimized mass ratios of pomegranate peel to Fe/La salt, the LaFeO3/HTCC photocatalyst achieved a highest nitrate removal of 94.6% and an ammonia selectivity of 88.7% under visible light irradiation. This work provides the approach for the photocatalytic synthesis of ammonia from residual nitrate pollutants.