Multiply Nano-Twinned Copper as a "Dual-Site Cooperative" Catalyst for Enhanced Electrocatalytic Nitrate Reduction to Ammonia.

Abstract

To advance the electrocatalytic nitrate reduction reaction (NIRR) to ammonia, it is essential to rationally regulate the kinetics of active hydrogen (H^*). Nevertheless, an in-depth understanding of H^* generation, transfer, and utilization remains elusive, which impedes exploring strategies for optimizing H^* dynamics. In this study, a copper nanocrystalline is developed with a multiply nano-twinned structure (MNTs-Cu) using a "dual nonequilibrium" strategy to optimize H^* dynamics and enhance NIRR performance. Experimental and theoretical studies show that MNTs-Cu functions as a "dual-site cooperative" catalyst, addressing the H^* supply-consumption balance to boost ammonia electrosynthesis. Specifically, the Cu sites are responsible for the activation of nitrate, while the nano-twinned structure serves as an "active hydrogen hub" to facilitate the generation, transfer, and utilization of H^*. The MNTs-Cu catalyst achieves a high NH₃ yield of 112.03 mg h^-1 cm^-2 at -0.7 V vs RHE, and notably, it can continuously maintain a high FE_NH3 of >99% within the high potential range from -0.7 to -0.9 V vs RHE. This work provides a novel pathway for optimizing H^* behavior through structural engineering, offering insights for advancing NIRR and other hydrogenation reactions.