fig1
Figure 1. Cation-dependent HER activity and Raman spectra on polycrystalline Pt and Au. Panels (A-C) show Pt and panels (D-F) show Au in 0.1 M LiOH, NaOH, and KOH. (A and D) Polarization curves after post-measurement iR correction. (B and E) Overpotential magnitudes at a cathodic current density of -5 mA cm-2. (C and F) Raman O-H stretching spectra at -0.05 V vs RHE and their three-component fits. The lower- and intermediate-wavenumber components are assigned phenomenologically to four- and two-coordinated hydrogen-bonded water, respectively. The high-wavenumber component is associated with weakly hydrogen-bonded cation-hydrated water. The numerical labels in (C and F) are the integrated area percentages of the high-wavenumber component: 100% × Aweak/(Astrong + Amoderate + Aweak). In LiOH, NaOH, and KOH order, these values are 2.6%, 6.3%, and 9.4% for Pt and 2.9%, 5.1%, and 7.2% for Au. They quantify fitted spectral contributions, not molecular population fractions.
