Unveiling the Catalytic Activity and Selectivity by Tuning the Coordination Environment of Cu Embedded on the WX2 (XS, Se, and Te) Monolayer for the Nitric Oxide Reduction Reaction: Insights from the DFT Approach

In this work, the effect of the coordination environment in Cu embedded in an X-vacant WX2 (X = S, Se, and Te) monolayer for the electrochemical NO reduction reaction (NORR) is investigated using the dispersion-corrected density functional theory (DFT-D3) approach. The stability of the Cu-WX2 single-atom catalyst (SAC), NO adsorption configurations, and different reaction pathways for the electroreduction of NO to NH3 are systematically examined. The catalytic activity and NH3 selectivity are investigated at both low and high NO coverages by analyzing various descriptors such as the density of states, charge density difference, crystal orbital Hamilton population (COHP), and Gibbs free energy change. The major NORR competing with the hydrogen evolution reaction (HER) and also the byproducts like N2O and N2 formation are greatly suppressed by our Cu-WX2 SACs. Among three different SACs, Cu-WTe2 shows an excellent catalytic performance with the lowest limiting potential of −0.26 V, which follows the most favorable N-distal reductive pathway in their free energy profile. Overall, our results may pave the way for developing a single-atom catalyst under ambient conditions for ammonia synthesis and also offer directions for the rational design of a highly efficient NORR electrocatalyst.

本研究采用色散校正密度泛函理论（dispersion-corrected density functional theory, DFT-D3）方法，探究了嵌入X空位WX₂（X=S、Se、Te）单层中的铜（Cu）配位环境对电化学NO还原反应（electrochemical NO reduction reaction, NORR）的影响。本研究系统考察了Cu-WX₂单原子催化剂（single-atom catalyst, SAC）的稳定性、NO吸附构型，以及NO电还原生成NH₃的多条反应路径。通过分析态密度（density of states）、电荷密度差（charge density difference）、晶体轨道哈密顿布居（crystal orbital Hamilton population, COHP）以及吉布斯自由能变（Gibbs free energy change）等多种描述符，研究了低NO覆盖度与高NO覆盖度下的催化活性与NH₃选择性。本研究设计的Cu-WX₂单原子催化剂可有效抑制与析氢反应（hydrogen evolution reaction, HER）竞争的主要NORR路径，以及N₂O、N₂等副产物的生成。在三种单原子催化剂中，Cu-WTe₂表现出最优的催化性能，其极限电位（limiting potential）最低，仅为-0.26 V，且其自由能谱中最优势的反应路径为N-远端还原路径（N-distal reductive pathway）。综上，本研究结果为常温常压下合成氨的单原子催化剂开发提供了可行思路，同时也为高效NORR电催化剂的理性设计指明了方向。