Pulsed electro-catalysis enables effective conversion of low-concentration nitrate to ammonia over Cu2O@Pd tandem catalyst

Electro-catalytic conversion of nitrate (NO 3 - ) to ammonia (NH 3 ) via the Nitrate Reduction to Ammonia (NORA) process represents a promising strategy for both ammonia synthesis and environmental remediation. Despite its potential, the efficiency of low-concentration NORA is often hindered by mass transfer limitations, competing byproducts (N 2 and NO 2 - ), and side reactions such as hydrogen evolution . This study introduces a novel pulsed electro-synthesis technique that alternates the potential to periodically accumulate and transform NO 2 - intermediates near a Cu2O@Pd electrode, enhancing the NORA process. Compared with that under potentiostatic conditions, the Cu 2 O@Pd electrodes exhibited a higher NORA activity under the optimized pulsed condition, where a NH 3 -N Faradaic efficiency (FE) of 81.2%, a yield rate of 1.08 mg h -1 cm -2 and a selectivity efficiency (SE) of 81.5%, were achieved. In-situ characterization revealed an enhancement mechanism characterized by optimized adsorption of the key *NO intermediate, followed by the hydrogenation path “*N → *NH → *NH 2 → *NH 3 ”. Further investigations indicated the electro-catalytic synergies between Pd sites and Cu species, where the Pd atoms were the reaction sites for the H adsorption while the Cu species were responsible for the NO 3 - activation. This research offers a novel insight into a method of enhancing low-concentration NORA.