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 as 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.

We present the first bubble-nucleation-based electrochemical method for the selective and sensitive detection of surfactants. Our method takes advantage of the high surface activity of surfactant analyte to affect the electrochemical bubble nucleation and then transduces the change in nucleation condition to electrochemical signal for determining the surfactant concentration. Using this method, we demonstrate the quantitation of perfluorinated surfactants in water, a group of emerging environmental contaminants, with a remarkable limit of detection (LOD) down to 30 μg/L and a linear dynamic range of over 3 orders of magnitude. With the addition of a preconcentration step, we have achieved the LOD: 70 ng/L, the health advisory for perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) in drinking water established by the U.S. Environmental Protection Agency. The experimental results are in quantitative agreement with our theoretical model derived from classical nucleation theory. Our method also exhibits an exceptional specificity for the surfactant analytes even in the presence of 1000-fold excess of nonsurfactant interference. This method has the potential to be further developed into a universal electrochemical detector for surfactant analysis because of its simplicity and the surface-activity-based detection mechanism.

We present a facile perfluorooctanesulfonate-modulation strategy with a precisely controlled dissolved-gas concentration at the electrode/gas/electrolyte interface for enhanced HER.