Dynamic dissolution-reorganization of molybdenum triggers synergistic electrocatalysis on copper for efficient nitrate-to-ammonia conversion
Xuran Mao, Yanbing Huang, Yue Xiao, Xun Liu, Yan Pei, Qianwen Chen, X.H. Wang, Wen Guo, Hong‐Bing Yang, Fuxi Bao
Abstract
Developing highly efficient and robust electrocatalysts to enhance the kinetics of electrochemical nitrate reduction reaction (NO 3 RR) to ammonia is crucial for realizing the conversion and storage of green electrochemical ammonia energy. Herein, we constructed a molybdenum-doped metallic copper electrocatalyst (Cu-Mo 0.2 /NF) and systematically investigated the pivotal role of molybdenum dynamic recombination in enhancing the kinetics of the NO 3 RR. In situ Raman spectroscopy, XPS and ICP-OES reveals that Mo dissolves during the NO 3 RR process and recombines into Mo 2 O 7 2- species, which are adsorbed onto the surface of the electrocatalyst. The experimental results combined with DFT calculations indicates that this dynamic dissolution, reorganization, and adsorption process of Mo significantly activates *NO 3 , thereby greatly enhancing the kinetics of *NO 3 reduction to *NO 2 . Furthermore, Differential electrochemical mass spectrometry (DEMS) and in situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) elucidate the NO 3 RR pathway: *NO 3 → *NO 2 → *NO → *NOH → *N → *NH → *NH 2 → *NH 3 . This reaction mechanism, which circumvents high-energy-barrier step (NO → N 2 O), endows the electrocatalyst with superior kinetics and high selectivity. Benefiting from the dynamic dissolution and redeposition of Mo and the advantages of the reaction pathway, the electrocatalyst achieves a record ammonia yield ( 1.55 mmol h -1 cm -2 ) with near-unity Faradaic efficiency ( 98.99% ), and 30 h stability.