Enabling High Performance in a Positive Potential of Nitrate‐to‐Ammonia Electrocatalysis Over Mesoporous Core@Shell Cu ₂ O/Cu@PdCu Nanozyme

Abstract

Abstract Electrocatalytic tandem nitrate reduction to ammonia (NO 3 − ‐to‐NH 3 ) offers a promising pathway for energy and environmental sustainability. Although considerable efforts have been presented to modulate the reaction pathways for enhanced NO 3 − ‐to‐NH 3 electrocatalysis, these advances often require relatively high overpotentials to balance yield rate and selectivity of NH 3 , resulting in a remarkable energy inefficiency. Inspired by enzyme catalysis in nature, herein a tandem enzyme‐like electrocatalyst is designed consisting of a core of Cu 2 O/Cu heterojunction surrounded by mesoporous PdCu shell (Cu 2 O/Cu@mesoPdCu) that accelerated NO 3 − ‐to‐NH 3 electrocatalysis in positive potentials. Impressively, Cu 2 O/Cu@mesoPdCu nanozymes hold superior performance for robust NH 3 electrosynthesis in a fairly positive potential of 0.10 V (versus reversible hydrogen electrode), having Faraday efficiency of 96.2%, yield rate of 13.3 mg h −1 mg −1 , and half‐cell energy efficiency of 46.0%. Kinetic studies, in situ spectra and density functional theory calculations revealed that Cu 2 O/Cu core preferentially adsorbed NO 3 − and further reduced to *NO 2 , while active hydrogen radicals enriched on PdCu shell promoted multistep hydrodeoxygenation of *NO 2 to NH 3 within “semi‐closed” mesoporous microenvironment, both of which synergistically enabled tandem electrocatalysis in positive potentials. Moreover, this enzyme‐like electrocatalyst disclosed better NO 3 − ‐to‐NH 3 performance in a more energy‐efficient manner when coupling with more thermodynamically favorable ethanol oxidation reaction.