A recent review on photochemical and electrochemical nitrogen reduction to ammonia: Strategies to improve NRR selectivity and faradaic efficiency

The photo/electrocatalytic nitrogen reduction reaction (NRR), which enables NH 3 synthesis in ambient circumstances, could replace the Haber-Bosch process (HB) and provide a solution for green nitrogen fixation. However, the extremely high chemical stability of N N bonds and the competition from the hydrogen evolution reaction (HER) significantly restrict the improvement of NRR activity. Thus, the advancement of photocatalysts and photoelectrocatalysts is crucial to the success of nitrogen photoreduction. Therefore, it is crucial to comprehend the foundations of nitrogen reduction procedures as well as the obstacles preventing catalyst advancement. As a result, one of the most active areas of research in the science of catalysis has always been the hunt for effective catalysts that can convert N 2 to NH 3 under benign conditions and with minimal energy input. Researchers have enhanced the catalytic sites of photocatalysts and located appropriate supporting materials to activate N 2 molecules, which significantly increases the efficiency of photo/electrocatalytic N 2 synthesis of ammonia. This review summarizes and compares several approaches used to synthesize ammonia. Secondly, the heterogeneous catalyst mechanism for the NRR was discussed. Then, several photo/electrocatalytic materials that were developed and designed for NRR including oxides, sulfides, transition metal carbides, and transition metal nitrides were surveyed. After that, kinetic and thermodynamics regulations for enhancing the NRR selectivity and faradaic efficiency of the NRR were discussed in more detail. Finally, by fusing theoretical predictions with experiment findings, this study provides useful direction for the rational design of photocatalysts and electrocatalysts for NRR. We are hoping that this review may pique more people's curiosity about the still-under-researched but exciting topic of NRR.