Efficiency of the Electrocatalytic Nitrate Reduction to Ammonia: Do the Surface Nanostructures Play an Essential Role?

The degradation of electrochemical materials during energy conversion and storage, in particular the electrocatalyst materials, is becoming increasingly important. The selection and design of sustainable materials is an important task. This work examines the synthesis, characterization, and application of an electrocatalyst (based on an amorphous alloy Co75Si15Fe5Cr4.5) having a structured surface in the form of nanocells for a “green” nitrate reduction reaction (NO3RR), which can serve as an alternative to the well-known Haber-Bosch process for the synthesis of ammonia. The material for the electrocatalyst was obtained by anodizing the alloy in the ionic liquid BmimNTf2 and characterized by using a combination of modern physicochemical and electrochemical methods. The Faradaic efficiency (FE) for the nanocell catalyst exceeds by more than three-fold and seven-fold catalyst with a polished surface and the initial catalyst having a natural oxide on the surface, respectively. A mechanism of this reaction on the studied electrocatalysts with structured and non-structured surfaces is proposed. It is mentioned that the nanocell electrocatalyst is an extremely stable material that passes all tests without visible changes. The authors consider their work as a starting point for the application of a nanostructured Co-electrocatalyst in NO3RR.