As the electrolytic solution, 1 mol dm -3 KOH solution (Sigma Aldrich) prepared with ultrapure deionized water was used in all experiments. All the measurements were done at room temperature. In this work, potentials are referred to SCE, and to calculate overpotentials for HER, potentials are converted to the Reversible Hydrogen Electrode (RHE) scale as E RHE = E SCE + 0.244 V + 0.059 V × pH (pH = 13.45). Electrolyte resistance was corrected using hardware settings, but only up to 80 % of the resistance value, determined using single-point impedance measurement at -1 V vs. SCE. If a higher percentage of iR drop was corrected, the measurements were unstable. HER measurements were done using cyclic voltammetry at a sweep rate of 10 mV s -1 . Before the potential sweep, the electrode was held -1 V vs. SCE until current dropped below 1 μA cm -2 . No anodic excursions of the working electrode were allowed before the HER measurements unless explicitly stated otherwise.