Heterostructure‐Derived Heterovalent Fe(OH)<sub>2</sub>/Fe Pair Sites: Tuning Adsorption of Intermediates and Enhancing Utilization of Atomic <sup>*</sup>H for Efficient Nitrate Reduction to Ammonia
Runlin Xia, Wenjing Wang, Yuxuan Zhou, Qingxin Guan, Yuping Liu, Wei Li
Abstract
Abstract Electrocatalytic nitrate reduction (NO3RR) to valued ammonia is an ideal supplementary route to the Haber–Bosch method and a strategy for the removal and utilization of nitrate pollutants. However, due to the fact that NO3RR goes through a complicated multi‐electron/proton transfer, catalysts with monovalent metal sites are difficult to tackle multitasking that it involves, leading to unsatisfactory nitrate conversion efficiency and ammonia selectivity. Herein, heterovalent Fe(OH) 2 /Fe pair sites supported onto carbon nanotubes (Fe(OH) 2 /Fe@CNTs) are presented via electrochemical reconstruction of CNTs‐supporting FeS/Fe 2 C heterostructure. Fe(OH) 2 /Fe@CNTs exhibits a high NH 3 yield rate of 0.67 mmol h −1 cm −2 with a FE of 95.1% at −0.4 V versus RHE, which is mainly attributed to the regulated electronic structure and cooperation of heterovalent iron pair sites. Meanwhile, the adsorption of nitrogen‐containing species is adjusted and the utilization of * H is enhanced. Moreover, a balanced content of Fe(OH) 2 and Fe creates “buffering effect” to maintain its activity and stability. Theoretical calculations combined with in situ FTIR and in situ Raman spectra reveal a novel multiple reaction pathway on heterovalent Fe(OH) 2 /Fe pair sites, entirely different from a single pathway on monovalent Fe or Fe(OH) 2 . Clearly, this study offers a creative strategy for the design of advanced catalysts with multivalent metal sites.