中科院大连化物所王爱琴团队报道了铜单原子到纳米颗粒的电位驱动重组促进硝酸盐电化学还原成氨。相关研究成果于2022年6月29日发表于国际顶尖学术期刊《美国化学会杂志》。

重组在热催化中普遍存在，对于确定真正的活性位点至关重要，但在电催化中的研究较少。

该文中，通过使用Operato X射线吸收光谱和高级电子显微镜，揭示了在硝酸盐电化学还原为氨的过程中，合成的Cu–N4单原子位置重新构造为约5 nm的纳米颗粒，这是一条与等离子体辅助氮氧化相结合的绿色氨生产路线。研究人员发现Cu²⁺还原为Cu⁺和Cu⁰以及随后Cu⁰单原子的聚集与NH₃生成速率的提高同时发生，这两个过程都是由施加电势从0.00 V到1.00 V的转换驱动的。氨的最大产率达到4.5 mg cm^–2 h^–1（12.5 mol_NH3 g_Cu^–1 h^–1），在1.00 VvsRHE下，法拉第效率为84.7%，优于之前报道的大多数其他铜催化剂。

电解后，聚集的铜纳米颗粒可逆地分解成单个原子，然后暴露在环境大气中恢复到Cu–N4结构，这掩盖了反应过程中潜在的诱导重组。Cu⁰百分比和氨法拉第效率随外加电位的同步变化表明，Cu纳米粒子是硝酸盐还原为氨的真正活性中心，这与沉积后的Cu-NP催化剂和密度泛函理论计算结果一致。

附：英文原文

Title: Potential-Driven Restructuring of Cu Single Atoms to Nanoparticles for Boosting the Electrochemical Reduction of Nitrate to Ammonia

Author: Ji Yang, Haifeng Qi, Anqi Li, Xiaoyan Liu, Xiaofeng Yang, Shengxin Zhang, Qiao Zhao, Qike Jiang, Yang Su, Leilei Zhang, Jian-Feng Li, Zhong-Qun Tian, Wei Liu, Aiqin Wang, Tao Zhang

Issue&Volume: June 29, 2022

Abstract: Restructuring is ubiquitous in thermocatalysis and of pivotal importance to identify the real active site, yet it is less explored in electrocatalysis. Herein, by using operando X-ray absorption spectroscopy in conjunction with advanced electron microscopy, we reveal the restructuring of the as-synthesized Cu–N4 single-atom site to the nanoparticles of ～5 nm during the electrochemical reduction of nitrate to ammonia, a green ammonia production route upon combined with the plasma-assisted oxidation of nitrogen. The reduction of Cu2+ to Cu+ and Cu0 and the subsequent aggregation of Cu0 single atoms is found to occur concurrently with the enhancement of the NH3 production rate, both of them are driven by the applied potential switching from 0.00 to 1.00 V versus RHE. The maximum production rate of ammonia reaches 4.5 mg cm–2 h–1 (12.5 molNH3 gCu–1 h–1) with a Faradaic efficiency of 84.7% at 1.00 V versus RHE, outperforming most of the other Cu catalysts reported previously. After electrolysis, the aggregated Cu nanoparticles are reversibly disintegrated into single atoms and then restored to the Cu–N4 structure upon being exposed to an ambient atmosphere, which masks the potential-induced restructuring during the reaction. The synchronous changes of the Cu0 percentage and the ammonia Faradaic efficiency with the applied potential suggests that the Cu nanoparticles are the genuine active sites for nitrate reduction to ammonia, which is corroborated with both the post-deposited Cu NP catalyst and density functional theory calculations.

DOI: 10.1021/jacs.2c02262

Source: https://pubs.acs.org/doi/10.1021/jacs.2c02262