碱性体系中金电极表面硫氰根离子的宽带和频光谱研究

本文使用宽带和频光谱研究不同电位下碱性溶液中多晶金电极表面硫氰根离子（SCN^-）的吸附行为. 在-1.1 V ~ 0.2 V（vs. SCE），C-N伸缩振动的Stark斜率的变化表明，随着电位正移，SCN^-在金电极表面从N端吸附变为S端吸附. 在较正电位下，C-N伸缩振动具有Fano线型. 这是因为金的费米能级随电位的正移而降低，和频过程中金的电子跃迁方式从带内跃迁（sp→sp）变为带间跃迁（d→sp），造成金基底与表面吸附SCN^-和频信号的相对相位改变. 实验表明，通过研究和频光谱线型随电位的变化可以获取电极表面电子能级相对位置的信息.

Broadband Sum-Frequency Generation Spectroscopic Invstigations of Thiocyanate on Polycrystalline Au Electrode in Alkaline Solutions

Broadband sum frequency generation (BB-SFG) spectroscopy has been used to investigating the potential-dependent adsorption behaviors of thiocyanate ions on polycrystalline Au electrode in alkaline solutions. During the positive scan, a change in the Stark slope (dω_C-N/dE) for C-N stretching mode can be observed in the range of -1.1 V ~ 0.2 V (vs. SCE), which implies that the orientation of adsorbed thiocyanate ions at Au electrode surface changes from N-bound (dω_C-N/dE=45 cm^-1·V^-1) form to S-bound (dω_C-N/dE = 16.2 cm^-1·V^-1) form . At more positive potentials, the electrons in Au are ongoing interband transition, from d-band to sp-band, instead of intraband transition, from sp-band to sp-band, during the SFG process, and this difference will change the relative phase between the substrate and the adsorbed SCN- SFG signals. As a consequence, when the applied potential is more positive, the lineshapes of the BB-SFG spectrum for C-N stretching mode become Fano (dispersive) lineshapes. From the potential-dependent BB-SFG lineshapes, the information about relative positions for the electric energy levels of the electrode surface can be obtained.