Integrated Cascade Catalysts for Electrochemical Nitrate Reduction to Ammonia
Jingwen Xu, Hengjie Liu, Shengbo Zhang, Qia Peng, Shuang Liu, Jinghao Chen, X. Wang, W. P. Wang, Hongxu Liu, Zehui Xie, L. Song, Ke Li, Wei Chen
Abstract
Electrocatalytic nitrate reduction reaction (NO 3 – RR) powered by renewable energy sources offers a promising approach to achieve ammonia (NH 3 ) synthesis with zero-carbon emission. However, sluggish proton-coupled electron transfer and byproduct formation challenge efficient NH 3 synthesis. Here, we construct an integrated cascade catalytic system to elucidate the governing principles of active hydrogen (*H) generation and utilization during NO 3 – RR. A representative catalyst, composed of atomically dispersed Fe sites anchored on an N-doped carbon matrix and encapsulated Ru nanoparticles, exhibits an NH 3 yield up to 2336.43 μg NH3 h –1 mg cat –1 while maintaining a Faradaic efficiency of 96.03% at a low potential of 0 V vs RHE. In addition, operando SR-FTIR spectroscopy and DFT calculations reveal that electron transfer from Fe atom to Ru particle not only enhances the affinity of Fe sites for NO x – species but also enriches H coverage on Ru sites, thereby accelerating hydrogenation steps and sustaining a steady *H generation-consumption cycle. This work reveals the mechanistic origin of active hydrogen in tandem catalytic structures and provides fundamental insights for advancing highly selective, energy efficient, and durable NH 3 electrosynthesis and wastewater treatment.