A New Overpotential — Capacitance Mechanism for H(2) Electrode

The H(2) electrode is commonly assumed to be a half-cell, 2 H(+) + 2e == H(2), and explained by the Nernst equation. We cannot assume that the H(+) is easily reduced to H(2) in an H(2) saturated solution, and H(2) becoming oxidized to H(+) in a strongly acid solution against the equilibrium principle. How can the H(2) gas is involved from a basic solution where there is practically no H(+) ions? Another equilibrium has been postulated, H(2) (soln) = 2H (adsorbed on metal) = 2 H(+) + 2e. This paper reports the results of studying the H(2) electrode using various techniques, such as adsorption, bubbling with H(2), and N(2), charging, discharging, and recharging, replacing the salt bridge with a conducting wire, etc. An interesting overpotential was observed that bubbling H(2) into the solution caused a sudden change of potential to more negative without changing the solution pH. The H(2) may be replaced by N(2) to give a similar calibration curve without the overpotential. The results contradict the redox mechanism. When the Pt is separated by H(2) coating, it cannot act as a catalyst in the solution. Our results seem to explain the H(2) electrode mechanism as the combination of its overpotential and capacitance potential. Bubbling of H(2) or N(2) only removes interfering gases such as O(2) and CO(2). Since neither H(2) nor N(2) is involved in the potential development, it is improper to call the H(2) or N(2) electrode. A term of pH / OH Pt electrode, like the pH / OH glass electrode, is suggested.