Ni–Co bimetallic phosphide catalyst toward electrocatalytic ammonia synthesis under ambient conditions†

Electrocatalytic nitrate reduction reaction (NitRR) under ambient conditions is a promising sustainable and eco-friendly method for ammonia (NH₃) synthesis, which currently highly relies on the energy-consuming Haber–Bosch process with enormous CO₂ emissions. In this work, we report the synthesis of a Ni–Co bimetallic phosphide catalyst (NiCoP) using the traditional hydrothermal combined high-temperature phosphorization method. Compared with monometallic phosphides such as Ni₂P and CoP, the as-synthesized NiCoP catalyst with synergistic effects exhibits remarkable NitRR performance with the highest faradaic efficiency (FE) of 91.3 ± 4.4% at −1.2 V (vs. RHE) with the maximum NH₃ yield rate of 5553.4 ± 400.8 μg h⁻¹ cm⁻² at −1.4 V (vs. RHE). Further in situ different electrochemical mass spectrometry (DEMS) analysis is employed to identify the intermediate produced during the electrocatalytic NitRR process, confirming NiCoP as a promising electrocatalyst for NH₃ synthesis.