Intermetallic Compound and Solid Solutions of Co75Me25 (Me: Si, Fe, Cr) as Catalysts for the Electrochemical Reaction of Nitrate Conversion to Ammonia.

A sustainable reaction of electrocatalytic nitrate conversion in ammonia production (NO3RR) occurring under ambient conditions is currently of prime interest, as well as urgent research due to the real potential replacement of the environmentally unfavorable Haber-Bosch process. Herein, a series of electrocatalysts based on two-component cobalt alloys was synthesized using low-cost non-noble metals Co, Fe, Cr, and also Si. The samples of electrocatalysts were characterized and studied by the following methods: SEM, EDX, XRD (both transmission and reflection), UV-VIS spectroscopy, optical microscopy, linear (and cyclic) voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Beyond that, the determination of electrochemically active surface area was also carried out for all samples of electrocatalysts. Unexpectedly, the sample having an intermetallic compound (IMC) of the composition Co2Si turned out to be the most highly effective. The highest Faradaic efficiency (FE) of 80.8% at E = -0.585 V (RHE) and an ammonia yield rate of 22.3 µmol h-1 cm-2 at E = -0.685 V (RHE) indicate the progressive role of IMC as the main active component of the electrocatalyst. Thus, this study demonstrates the promise and enormous potential of IMC as the main component of highly efficient electrocatalysts for NO3RR. This work can serve primarily as a starting point for future studies of electrocatalytic conversion reactions in the production of ammonia using IMC catalysts containing non-noble metals.