Ag Cluster-Modified K0.5Na0.5NbO3 Piezocatalyst for Enhanced Electrochemical Dinitrogen Reduction Reaction

Abstract

Efforts in finding alternatives to Haber–Bosch process for chemical synthesis of ammonia still struggle with efficient N₂ activation. Piezoelectric materials are promising cocatalysts to enhance the chemical kinetics of dinitrogen (N₂) reduction through, built-in electric fields, upon mechanical activation, which can modulate the surface electrochemical potential. This work reports on the influence of piezoelectric potassium sodium niobate (K_0.5Na_0.5NbO₃, KNN) as a lead-free cocatalyst for the electrochemical nitrogen reduction reaction to ammonia (NH₃) under mild conditions, on a silver (Ag) catalyst. For piezoactivation, modified H-cell is engineered with the working electrode (Ag/KNN), enabling external mechanical actuating during electrochemical process. The results demonstrate that transient dipoles generated on the KNN surface through localized electric field improve threefold NH₃ production (3.6 μg h⁻¹ cm⁻²) and a Faradaic efficiency up to 75%. Piezoinfluence is investigated through actuation-induced, linear sweep voltammetry, electrochemical impedance spectroscopy, chronoamperometry, and open-circuit potential measurements.