A Review on Advances in Electrocatalytic N2 Reduction to Ammonia

Abstract

Ammonia is one of the most important industrial chemicals which is prepared by the traditional Haber–Bosch process. Haber–Bosch process is an expensive process requiring higher temperature, pressure, and a lot of energy. Electrocatalytic nitrogen reduction reactions (NRR) have gained a lot of interest as the alternate method for the production of ammonia. For obtaining a higher yield, higher Faradic efficiency (PE), inhibition of side reactions e.g., hydrogen evolution reaction (HER), and reducing the production cost for ammonia by NRR, selection of appropriate catalysts, cell layout, and electrolyte selection are important controlling parameters for the NRR. Non-metallic catalysts are preferred over noble metallic catalysts due to their lower cost, more resources, and characteristic dorbital electron but have the issue of low selectivity due to the higher HER. The selectivity for the NRR can be improved by employing the catalysts with higher absorption of N2. PEM-type cells and the back-to-back cells are used to inhibit the HER. Apart from these factors, NRR is also dependent on other factors to obtain better experimental results e.g., no nitrides, removing the ammonia from contaminants sites, and controlling the experiment time.