Boron-Enriched Benzene Boronic Acid Based Hyper-Cross-Linked Polymer for Selective Electrocatalytic N₂ Reduction to Ammonia

Abstract

The nitrogen (N 2 ) electro-reduction to ammonia (NH 3 ) at ambient conditions is considered a promising substitute for the Haber−Bosch (H−B) process. Considering the low Faradaic efficiency (FE) and slow reaction kinetics of the nitrogen reduction reaction (N 2 RR), it is important to design robust catalysts that can address the above-mentioned challenges. A boron-enriched hyper-cross-linked polymer (Poly-BBA) based on benzene boronic acid synthesized by a fast microwave-assisted approach has reportedly been used as metal-free electrocatalyst for efficient N 2 electro-reduction to NH 3 . The Poly-BBA was synthesized using microwave power of 400 W at 45 °C for 30 min and aging at 100 °C for 30 min. The successful synthesis of Poly-BBA was conducted by state-of-the-art analytical techniques. The N 2 sorption analysis demonstrates a hierarchical porous structure with a high SA BET of 1080 m 2 g −1 and a total pore volume of 0.7 cm 3 g −1 . The Poly-BBA shows selective reduction of N 2 to NH 3 with an FE of 21.9% in 0.05 M H 2 SO 4 solution at −0.5 V vs RHE. The presence of boron in the synthesized material resulted in the redistribution of electron density and provided electrondeficient sites for adsorption and activation of N 2 molecules.