Broader energy distribution of CO adsorbed at polycrystalline Pt electrode in comparison with that at Pt(111) electrode in H2SO4 solution confirmed by potential dependent IR/visible double resonance sum frequency generation spectroscopy

•Electrochemical SFG spectroscopy is an efficient in situ probe of electronic structure at electrochemical interface.•Electrooxidation performances of CO adsorbed on polycrystalline Pt and Pt(111) electrodes were compared.•The enhanced SFG signal of CO on Pt electrodes was observed due to a vibrational-electronic double resonance effect.•The broader energy distribution of 5sa state of CO on polycrystalline Pt than on Pt(111) is proved by SFG results.

Electrochemical cyclic voltammetry and potential dependent double resonance sum frequency generation (DR-SFG) spectroscopy were performed on CO adsorbed on polycrystalline Pt and Pt(111) electrodes in H2SO4 solution to examine the effect of substrate on the electronic structure of CO. The dependence of SFG intensity on potential and visible energy for atop CO band was observed on both polycrystalline and single crystalline Pt electrodes. Enhancement of the SFG intensity was determined to be a direct result of a surface electronic resonance of the visible/SF light with the electronic transition from Fermi level of Pt to the 5σa anti-bonding state of adsorbed CO, in agreement with previous results. Interestingly, when compared to the Pt(111) electrode, the distribution width of the intensity enhancement region on polycrystalline Pt is broader than on Pt(111). This suggests that the energy distribution of the 5σa state of CO on polycrystalline Pt surface is broader than that on Pt(111) due to the complex surface structure of the polycrystalline Pt electrode.

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