Conductive polymer protection strategy to promote electrochemical nitrate reduction to ammonia in highly acidic condition over Cu-based catalyst

Abstract

Electrochemical nitrate reduction (NO3-RR) is a promising way to produce ammonia by alternating Haber-Bosch process. As one promising catalyst, copper suffers from low activity and instability in acidic electrolyte that hinders practical applications. Herein, we report a conductive polymer protection strategy by decorating polypyrrole on Cu nanoparticles (Cu-PPy), achieving high NO3-RR efficiency under strong acidic conditions. In 0.5 M H2SO4, Cu-PPy exhibits high NH3 yield rate of 0.55 mmol h−1 cm−2 with NH3 selectivity of 99.99 % and FE of 96.0 % at high NO3– conversion. Experimental and theoretical results reveal that PPy plays a pluripotent role for the enhanced NO3-RR, consisting of protecting Cu from corrosion in highly acidic electrolyte, promoting the adsorption of NO3– and NO2– in local environment, stabilizing Cu in intermediate valence state, and accelerating the electron transfer rate. Furthermore, a co-production system of NH3 and adipic acid is constructed and achieves high combined electron efficiency.