Heterogeneous electrocatalytic oxidation of ammonia to hydrazine with a polymer-supported ruthenium-based catalyst

Abstract

The electrochemical oxidation of ammonia to hydrazine presents a green alternative to traditional peroxide-based processes, avoiding harsh oxidants and simplifying purification. However, achieving selective N–N bond formation in heterogeneous systems remains a major challenge, due to dominant overoxidation pathways and limited control over catalytic intermediates. Here we report a polymer-supported, single-site ruthenium catalyst that enables the direct electrochemical conversion of ammonia to hydrazine with a faradaic efficiency of 7.9%, maintaining stable performance for over 6 hours. The well-defined coordination environment and tailored microenvironment around the isolated Ru sites facilitate a nucleophilic attack mechanism, as evidenced by reaction order and kinetic isotope effect studies. This system represents the first example of a heterogeneous catalyst capable of selectively oxidizing ammonia to hydrazine. Our findings highlight how rational design of the catalytic microenvironment—through the integration of molecularly precise units into porous polymeric frameworks—can steer product selectivity in complex electrocatalytic transformations, offering a generalizable strategy for developing heterogeneous systems with molecular-level control.