Huo Sheng-Juan, Xue Xiao-Kang, Yan Yan-Gang, Li Qiao-Xia, Ma Min, Cai Wen-Bin, Xu Qun-Jie, Osawa Masatoshi
Shanghai Key Laboratory for Molecular Catalysis and Innovative Materials and Department of Chemistry, Fudan University, Shanghai 200433, China.
J Phys Chem B. 2006 Mar 9;110(9):4162-9. doi: 10.1021/jp0566966.
Surface-enhanced infrared absorption spectroscopy (SEIRAS) in the attenuated-total-reflection configuration (ATR-SEIRAS) has been applied for the first time to Ni electrodes. SEIRA-active Ni electrodes were obtained through initial chemical deposition of a 60-nm-thick Au underlayer on the reflecting plane of an ATR Si prism followed by potentiostatic electrodeposition of a 40-nm-thick Ni overlayer in a modified Watt's electrolyte. The Ni nanoparticle film thus obtained exhibited exceptionally enhanced IR absorption for the surface probe molecule CO while maintaining unipolar and normally directed bands. With the advantages of ATR-SEIRAS, free H2O molecules coadsorbed with CO at the Ni electrode were revealed, and their role in the electrooxidation of the CO adlayer at the Ni electrode is discussed. In addition, the conversion of bridge to linearly bonded CO at Ni electrode in a neutral solution was clearly identified upon electrooxidation of the CO adlayer. ATR-SEIRAS was also used to characterize the adsorption configuration of a pyridine adlayer at the Ni electrode. Both A1 and B1 modes of adsorbed pyridine were detected with comparably large intensities, essentially maintaining the spectral feature of pyridine molecules rather than that of "alpha-pyridyl species", which strongly suggests an "edge-tilted pyridine" configuration present at the Ni electrode, a configuration intermediate between the "end-on pyridine" and "edge-on alpha-pyridyl" adsorption modes reported in the literature.
衰减全反射配置（ATR-SEIRAS）下的表面增强红外吸收光谱（SEIRAS）首次应用于镍电极。通过在ATR硅棱镜的反射面上初始化学沉积60纳米厚的金底层，然后在改良的瓦特电解液中恒电位电沉积40纳米厚的镍覆盖层，获得了具有SEIRA活性的镍电极。由此得到的镍纳米颗粒膜对表面探针分子CO表现出异常增强的红外吸收，同时保持单极且方向正常的谱带。借助ATR-SEIRAS的优势，揭示了在镍电极上与CO共吸附的游离H₂O分子，并讨论了它们在镍电极上CO吸附层电氧化中的作用。此外，在CO吸附层电氧化时，清晰地识别出中性溶液中镍电极上桥式CO向线性键合CO的转变。ATR-SEIRAS还用于表征镍电极上吡啶吸附层的吸附构型。检测到吸附吡啶的A₁和B₁模式强度相当大，基本保持了吡啶分子的光谱特征，而非“α-吡啶基物种”的特征，这强烈表明镍电极上存在“边缘倾斜吡啶”构型，该构型介于文献报道的“端基吡啶”和“边缘吡啶”吸附模式之间。
