Managing Active Hydrogen Species on Ternary Copper-Based Catalyst for Efficient Electrochemical Ammonia Synthesis from Nitrate.

The electrochemical nitrate reduction to ammonia (NO3RR) has garnered considerable interest as a highly promising route for value-added nitrate conversion. However, the efficiency of NO3RR is often limited by the inadequate supply of active hydrogen species (H*) and their preferential consumption via the competing hydrogen evolution reaction (HER), both of which stem from the lack of precise management of H*. Herein, we report a rationally designed ternary catalyst Pt@ZIF@Cu to achieve precise control and targeted utilization of H*. The spatially separated Pt and Cu sites serve as independent centers for H* generation and consumption, respectively. A ZIF layer is introduced as a hydrogen buffer, facilitating the efficient migration of H* from Pt sites to Cu sites with a reduced energy barrier, which ultimately enhances the NO3RR performance on the Cu surface while simultaneously suppressing HER at the Pt sites. The ternary Pt@ZIF@Cu exhibits superior NO3RR performance with an ammonia yield rate of up to 4.6 mmol h-1 mgcat-1 at -0.8 V (vs RHE) through meticulous H* management. Furthermore, it demonstrates enhanced performance (8.34 mmol h-1 mgcat-1) in a membrane electrode assembly (MEA) under ampere-level current densities, and enables the convenient preparation of high-purity solid ammonium products via Ar-stripping.