NiCu bimetallic catalyst for improved electrochemical synthesis of ammonia from nitrates

Introduction

One of the problems for the widespread using of hydrogen energy is the search for a replacement of well-known industrial technologies with green sustainable reactions. With regard to the potential replacement of the with high carbon emissions Haber Bosch ammonia synthesis (as one of the most used in the world), promising "nitrogen" electrochemical reactions have recently been proposed, such as direct reduction of dinitrogen (NRR) and reduction of nitrates/nitrites (NO₃RR and NO₂^-RR). However, the weak kinetics of ammonia formation and the expensive noble metal catalysts required for the process significantly limit these applications. Finding highly efficient catalysts from low-cost components that can eventually make these reactions suitable for practical applications is a difficult task and challenge. It is propose to test bimetal alloys based on non-noble (Ni and Cu: "NiCu-depositions") as electrocatalysts for the NO₃RR.

Experimental

NiCu-deposition samples were produced by electrochemical co-deposition from aqueous solutions of the corresponding salts. The characterization of NiCu-deposition samples were used of SEM, EDX, XRD. The voltammetry and chronoamperometry were used to determine the conditions for the synthesis reactions of ammonia with use the Autolab PGSTAT302N and PS-20 potentiostats.

Results and Discussion

The results show that the use of NiCu-deposition electrocatalysts is promising, Faradaic efficiency up to 60% and ammonia yield rate were achieved in the electrochemical reaction of ammonia synthesis. The 19 samples with different Cu to Ni ratios were studied, which made it possible to identify the most effective one (97.5 : 2.5 at%), which is associated with special nanostructures on the surface. The electrocatalysts may have the prospects for reducing CO₂ emissions by replacing the Haber Bosch process with eco-friendly "nitrogen" electrocatalytic reactions.

Acknowledgment.

The research was carried out at the expense of the grant of Russian Science Foundation (RSF) No 25-29-00488, https://rscf.ru/en/project/25-29-00488/.