Recent Progress and Outlook on Metal Phosphides for Nitrogen Gas Electrocatalytic Ammonia Synthesis

Ammonia (NH3) is a significant chemical and carbon-free energy carrier with important applications in industry and agriculture. Ammonia is primarily produced through the Haber–Bosch process (HB), which necessitates high temperatures and pressures, consumes a significant amount of energy, and produces a substantial amount of CO2. Electrocatalytic nitrogen reduction (NRR) for ammonia synthesis is a promising alternative to the HB process due to its mild reaction conditions and low energy consumption. However, the low ammonia yields reported for nonmetallic or metallic NRR catalysts are still far from the industrialization needs. In recent years, researchers have discovered that metal phosphides possess easy-to-regulate morphology, good stability, and synergistic properties that enable them to exhibit good electrocatalytic activity for the nitrogen reduction reaction. This emerging research direction has been identified as a promising approach for the development of high-performance NRR electrocatalysts. This article provides an overview of the advancements in the use of metal phosphides for electrocatalytic nitrogen reduction and ammonia synthesis in recent years. It briefly discusses their synthesis methods, structural modulation, and morphology modifications as well as the reaction mechanism and performance in nitrogen reduction reactions. Additionally, it addresses the potential challenges that metal phosphides may encounter in NRR applications and offers insights into future development prospects. This paper aims to propose innovative ideas for designing metal phosphide electrocatalysts to enhance the efficiency of electrocatalytic nitrogen reduction to produce ammonia.