High yield selective electrochemical conversion of N2 to NH3via morphology controlled silver phosphate under ambient conditions

Abstract

Development of a highly active catalyst for the synthesis of ammonia via the electrochemical dinitrogen reduction reaction (e-NRR) is an immense challenge. We report the modification of metallic Ag with inorganic phosphate to obtain Ag₃PO₄ as an effective electrocatalyst for the e-NRR in alkaline media under ambient conditions. The designed Ag₃PO₄ catalyst can effectually suppress the HER. The e-NRR activity was improved by fine-tuning the morphology by a template free one-pot synthesis. The synthesised Ag₃PO₄ having cuboidal morphology is shown to have superior activity and stability towards the e-NRR witnessed from a high faradaic efficiency of 26.67%, yield rate of 456.75 μg h⁻¹ mg_cat⁻¹ and TOF value of 0.46 h⁻¹ at a positive potential of 0 V vs. RHE in 0.1 M KOH. Careful examination of any N-contaminants present in catalyst/electrolyte/gas-feed is carried out by UV-vis spectroscopy and gas-purification methods prior to e-NRR measurements to eliminate any false NH₃ production. Also, the true source of NH₃ production is confirmed by means of ¹⁵N-isotope labelling experiments via¹H-NMR spectroscopy.