Dual Ion Leaching‐Induced Reconstruction of CuCo <sub>2</sub> S <sub>4</sub> Boosts Electrocatalytic Nitrate Reduction to Ammonia with Favorable Active Hydrogen Coverage
Feng Yu, Yuqiao Zhou, Kai Zhang, Ye Tian, Jiandong Yao, Wenjing Huang, Hao Wu, Yanguang Li, Shaoming Huang
Abstract
Abstract Electrochemical nitrate reduction (NO 3 ‒ RR) to ammonia (NH 3 ) offers a sustainable approach for NH 3 synthesis. However, inevitable catalyst reconstruction under NO 3 ‒ RR conditions complicates the identification of the true active species and the underlying reaction mechanisms. Herein, CuCo 2 S 4 nanoplates are fabricated as a model catalyst to investigate the reconstruction behavior and identify the active sites responsible for NO 3 ‒ RR. Experimental results reveal that the leaching of Cu and S triggers the transformation of CuCo 2 S 4 into Cu, S‐decorated Co(OH) 2 (denoted as Cu, S‐Co(OH) 2 ) during the NO 3 ‒ RR process. The derived Cu, S‐Co(OH) 2 exhibits a high NH 3 Faradaic efficiency of ≈99.5% across a broad potential range, with excellent cycling stability and chronopotentiometric durability. In situ Raman spectroscopy and kinetic analyses demonstrate that the superior performance is attributed to enhanced NO 3 − adsorption and optimal active hydrogen coverage. To demonstrate its practical application, a membrane electrode assembly (MEA) is assembled by incorporating Cu, S‐Co(OH) 2 as the cathode and IrO 2 as the anode, achieving stable operation at an industrial‐scale current density of 500 mA cm −2 with a Faradaic efficiency of ≈85% for green ammonia production.