Fig. 5: ATR-SEIRA spectra on Pd film in alkaline solutions with different cation species in the absence and presence of formate.

a The lower panel shows the ATR-SEIRA spectra collected in 0.1 M LiOH (or 0.1 M CsOH) on Pd film electrode at 0.1 V vs RHE, the reference spectrum is taken in the same electrolyte at 1.0 V vs RHE respectively. The upper panel shows the in situ ATR-SEIRAS spectra collected in 0.1 M LiOH + 0.1 M LiHCOO (or 0.1 M CsOH + 0.1 M CsHCOO) on Pd film 3 min after injection of formate, the reference spectrum is taken in the electrolyte before the injection of formate. b Deconvolution of the IR bands for interfacial water (νO-H) in the selected region of a. Source data are provided as a Source Data file.