Fuel from Waste: Electrosynthesizing Ammonia Directly from Agricultural Digestate through Ligand Isomerization

Abstract

We demonstrate that the catalytic metal centre for ammonia production can be selectively activated with only a slight alteration in ligand isomerization (α and β isomers), making it practical and effective even for agricultural effluents. With almost 90 % Faradaic efficiency, the β isomer generates approximately 0.64 mg h-1 cm-2 of ammonia. Energy-efficient ammonia recovery is made possible by the interfacial proton charge assembly that β-isomerization creates, which attracts the reacting nitrate and repels the competing hydronium ions. With minimal energy consumption, this isomerization approach can interconvert agricultural effluents into ammonia fuel, reaching up to 84 % of its theoretical yield and maintaining stability over 100 hours of continuous electrolysis.