H and CO Co-Induced Roughening of Cu Surface in CO2 Electroreduction Conditions.

The dynamic restructuring of Cu has been observed under electrochemical conditions, and it has been hypothesized to underlie the unique reactivity of Cu toward CO2 electroreduction. Roughening is one of the key surface phenomena for Cu activation, whereby numerous atomic vacancies and adatoms form. However, the atomic structure of such surface motifs in the presence of relevant adsorbates has remained elusive. Here, we explore the chemical space of Cu surface restructuring under coverage of CO and H in realistic electroreduction conditions, by combining grand canonical DFT and global optimization techniques, from which we construct a potential-dependent grand canonical ensemble representation. The regime of intermediate and mixed CO and H coverage─where structures exhibit some elevated surface Cu─is thermodynamically unfavorable yet kinetically inevitable. Therefore, we develop a quasi-kinetic Monte Carlo simulation to track the system's evolution during a simulated cathodic scan. We reveal the evolution path of the system across coverage space and identify the accessible metastable structures formed along the way. Chemical bonding analysis is performed on the metastable structures with elevated Cu*CO species to understand their formation mechanism. By molecular dynamics simulations and free energy calculations, the surface chemistry of the Cu*CO species is explored, and we identify plausible mechanisms via which the Cu*CO species may diffuse or dimerize. This work provides rich atomistic insights into the phenomenon of surface roughening and the structure of involved species. It also features generalizable methods to explore the chemical space of restructuring surfaces with mixed adsorbates and their nonequilibrium evolution.

在电化学条件下观察到了铜（Cu）的动态重构，并且据推测这是铜对二氧化碳电还原具有独特反应活性的基础。粗糙化是铜活化的关键表面现象之一，会形成大量原子空位和吸附原子。然而，在存在相关吸附物的情况下，此类表面结构基元的原子结构仍然难以捉摸。在此，我们通过结合巨正则密度泛函理论（grand canonical DFT）和全局优化技术，在实际电还原条件下探索了一氧化碳（CO）和氢（H）覆盖下铜表面重构的化学空间，并由此构建了一个与电位相关的巨正则系综表示。一氧化碳和氢的中等及混合覆盖区域——其中结构呈现出一些凸起的表面铜——在热力学上是不利的，但在动力学上是不可避免的。因此，我们开发了一种准动力学蒙特卡罗模拟，以追踪在模拟阴极扫描过程中系统的演化。我们揭示了系统在覆盖空间中的演化路径，并确定了在此过程中形成的可及亚稳结构。对具有凸起的Cu*CO物种的亚稳结构进行了化学键分析，以了解其形成机制。通过分子动力学模拟和自由能计算，探索了Cu*CO物种的表面化学，并且我们确定了Cu*CO物种可能扩散或二聚的合理机制。这项工作为表面粗糙化现象以及所涉及物种的结构提供了丰富的原子层面的见解。它还展示了一些可推广的方法，用于探索具有混合吸附物的重构表面的化学空间及其非平衡演化。