Tiara Ni Clusters for Electrocatalytic Nitrate Reduction to Ammonia with 97% Faradaic Efficiency
Xinrui Gu, Jingjing Zhang, Song Guo, Yifei Zhang, Liangliang Xu, Rongchao Jin, Gao Li
Abstract
High Resolution Image Download MS PowerPoint Slide The electroreduction of nitrate (NO 3 – ) for sustainable ammonia (NH 3 ) production has recently emerged as a green process to solve water contamination and produce valuable chemicals. In this study, we developed Ni 6 @CuFe-LDH composites comprising tiara Ni 6 (SC 2 H 4 COOH) 12 (Ni 6 ) clusters anchored on the edges of 2D CuFe-LDH (LDH: layered double hydroxides) nanosheets via electrostatic interactions. The Ni 6 @CuFe-LDH catalyst exhibits high electrochemical performance in nitrate reduction reaction (NO 3 RR). Specifically, the Ni 6 @CuFe-LDH gives rise to an excellent faradaic efficiency of ∼97%, significantly surpassing the ∼73% FE of the pristine CuFe-LDH, with the NH 3 productivity (0.91 mmol mg –1 h –1 ) being similar to that of the CuFe-LDH. Mechanistic studies reveal that the superior electrocatalysis of Ni 6 -based catalysts is primarily due to the synergistic interaction between Ni 6 clusters and CuFe-LDH, which alters the rate-determining step (RDS) of the desorption of *NH 3 species (for CuFe-LDH) to the *NO 3 → *NO 2 step (for Ni 6 @CuFe-LDH); this is corroborated by the control experiments of NO 2 RR, in situ Raman and infrared spectroscopies, and computational approaches. In all, these efforts push forward the NO 3 RR research to study the structure–property relationships from the micro/nano-level to the precise atomic-level.