Self-powered NH3 synthesis by trifunctional Co2B-based high power density Zn–air batteries

Abstract

The electrochemical production of NH₃ by Zn–air batteries is a viable and economical approach to realize sustainable and competent energy conversion. We report the environment friendly, cost-effective, and energy efficient sonochemical synthesis of amorphous Co₂B nanosheets for trifunctional electrocatalysis. The catalyst exhibits a high NH₃ yield rate (2.98 mg h⁻¹ mg_cat.⁻¹), F.E (20.45%), and TOF of 0.74 h⁻¹ at −0.3 V vs. RHE, thereby unveiling an outstanding performance for the artificial ammonia synthesis. The reliable and true NH₃ production is premediated by following rigorous protocol that involves the purification of gas supplies, elimination of N-contaminants, and quantification of NH₃ by different methods, UV-Vis spectroscopy and ¹⁵N₂ isotope labelling experiments. More interestingly, DFT calculations on the Co₂B catalyst surface shed light on the efficient NRR owing to the presence of Co active sites and possible HER suppression. The optimized Co₂B catalyst shows outstanding oxygen bifunctional activity. When employed as an air-cathode for Zn–air batteries, it exhibited remarkable electrocatalytic activity delivering an open circuit potential of 1.45 V with a high power density of 500 mW cm⁻² and an energy density of 1078 W h kg⁻¹, which can perform NH₃ generation with an overall NH₃ production yield rate of 1.048 mg h⁻¹ mg_cat.⁻¹.