Chen Kuo-Hao, Fathi Fatemeh, Maxson Tristan, Hossain Mezbah, Khisamutdinov Emil, Szilvási Tibor, Zeng Xiangqun, Li Zhihai
Department of Chemistry, Ball State University, Muncie, Indiana 47306, United States.
Department of Chemistry, Oakland University, Rochester, Michigan 48309, United States.
Langmuir. 2024 Mar 5;40(9):4914-4926. doi: 10.1021/acs.langmuir.3c03899. Epub 2024 Feb 22.
Electrochemical scanning tunneling microscopy (EC-STM) and electrochemical quartz crystal microbalance (E-QCM) techniques in combination with DFT calculations have been applied to reveal the static phase and the phase transition of copper underpotential deposition (UPD) on a gold electrode surface. EC-STM demonstrated, for the first time, the direct visualization of the disintegration of (√3 × √3)R30° copper UPD adlayer with coadsorbed SO while changing sample potential () toward the redox Pa2/Pc2 peaks, which are associated with the phase transition between the Cu UPD (√3 × √3)R30° phase II and disordered randomly adsorbed phase III. DFT calculations show that SO binds three oxygens to the bridge sites of the copper with sulfate being located directly above the copper vacancy in the (√3 × √3)R30° adlayer, whereas the remaining oxygen of the sulfate points away from the surface. E-QCM measurement of the change of the electric charge due to Cu UPD Faradaic processes, the change of the interfacial mass due to the adsorption and desorption of Cu(II) and SO, and the formation and stripping of UPD copper on the gold surface provide complementary information that validates the EC-STM and DFT results. This work demonstrated the advantage of using complementary experimental techniques (E-QCM and EC-STM) combined with simulations to obtain an accurate and complete picture of the dynamic interfacial adsorption and UPD processes at the electrode/electrolyte interface.
电化学扫描隧道显微镜（EC-STM）和电化学石英晶体微天平（E-QCM）技术与密度泛函理论（DFT）计算相结合，已被用于揭示金电极表面铜欠电位沉积（UPD）的静态相和相变。EC-STM首次展示了在将样品电位（）向氧化还原Pa2/Pc2峰变化时，（√3 × √3）R30°铜UPD吸附层与共吸附的SO分解的直接可视化，这与Cu UPD（√3 × √3）R30°相II和无序随机吸附相III之间的相变有关。DFT计算表明，SO通过三个氧原子与铜的桥位结合，硫酸根直接位于（√3 × √3）R30°吸附层中铜空位的上方，而硫酸根的其余氧原子则指向远离表面的方向。E-QCM对由于Cu UPD法拉第过程引起的电荷变化、由于Cu(II)和SO的吸附和解吸引起的界面质量变化以及金表面上UPD铜形成和剥离的测量提供了补充信息，验证了EC-STM和DFT的结果。这项工作展示了使用互补实验技术（E-QCM和EC-STM）结合模拟来获得电极/电解质界面动态界面吸附和UPD过程准确完整图像的优势。
