Air-stable iron phosphide catalysts for electric field-assisted low-temperature ammonia synthesis

Abstract

Ammonia synthesis is crucial for fertiliser production, future hydrogen storage, and hydrogen carrier production. Herein, we present a novel ammonia synthesis system using an iron phosphide catalyst with a DC electric field. Under mild reaction conditions (i.e., 400–430 K and 0.1 MPa of H₂), the air-stable iron phosphide catalyst exhibits superior performance to the conventional, unstable iron catalysts. Furthermore, this catalyst system enables precise control over ammonia production through on/off-switching of the DC electric field, demonstrating its potential for more dynamic and responsive synthesis processes. The structure–activity relationship of this catalytic system was also explored using various techniques such as TEM observation, XAFS analysis, and theoretical calculations. These findings open up promising avenues for the future development of next-generation on-site and low-temperature ammonia synthesis technologies that can be operated on demand.