Ionic Liquid–Engineered Core–Shell Polymer Nanospheres for Photocatalytic Nitrogen Reduction

Abstract

Resorcinol-formaldehyde resin (RF), a novel organic photocatalytic material, has seen extensive application in the photocatalytic generation of hydrogen peroxide in recent years, owing to its broad band gap structure and robust visible light absorption capabilities. The favorable positions of the conduction and valence bands of RF theoretically enable RF application in photocatalytic nitrogen fixation. Nevertheless, the limited solubility of nitrogen in water results in diminishing the effectiveness of photocatalytic nitrogen fixation. Herein, we presented a method to coat RF nanospheres with ionic liquid (RF@IL) exhibiting significant nitrogen enrichment capacity to develop a novel organic semiconductor material featuring a core-shell configuration. The abundant hydroxyl functional groups on the surface of RF nanospheres facilitate the coating of imidazolium ionic liquids, affording a nitrogen-rich thin film for the RF nanospheres and segregates the sites of nitrogen reduction and water oxidation, minimizing the recombination of photogenerated carriers and thereby enhancing the efficacy of the photocatalytic nitrogen fixation reaction. RF@IL facilitated photocatalytic nitrogen fixation, yielding 58.7 μmol/g of ammonia in 2 hours, which is 1.80 times greater than blank RF output of 32.6 μmol/g. Remarkably, after five testing cycles, RF@IL maintains substantial photocatalytic ammonia synthesis activity, underscoring the considerable influence of ionic liquids on photocatalytic processes. This study offers a viable solution to the issue of low nitrogen solubility impacting reaction performance in photocatalytic nitrogen fixation experiments.