Hydrogen Bubble Formation at Hydrogen-Insertion Electrodes

Here we report a fundamental study of the H-2 bubble formation mechanism on a model hydrogen-insertion material, Pd. We demonstrated that the current required for H-2 bubble formation at Pd electrodes was over 10 times higher than that at nonhydrogen-insertion metal electrodes (Au and Pt). Using a newly developed nanoelectrode platform, we measured the critical condition for H-2 bubble formation on different electrode materials. We discovered, for the first time, that the bubble formation on Pd required nearly the same supersaturation of dissolved H-2 on the electrode surface Au and Pt. The suppressed bubble generation on Pd relative to Au and Pt is caused merely by the hydrogen insertion into bulk Pd rather than the different surface energies of electrode materials. Our study provides new insights into the nanoscale H-2 bubble generation mechanism on hydrogen-insertion materials.