A New Overpotential — Capacitance Mechanism for H2 Electrode

Abstract: The H₂ electrode is commonly assumed to be a half-cell, 2 H⁺ 2e == H₂, andexplained by the Nernst equation. We cannot assume that the H⁺ is easily reduced to H₂ inan H₂ saturated solution, and H₂ becoming oxidized to H⁺ in a strongly acid solution againstthe equilibrium principle. How can the H₂ gas is involved from a basic solution where thereis practically no H⁺ ions? Another equilibrium has been postulated, H₂ (soln) = 2H(adsorbed on metal) = 2 H 2e. This paper reports the results of studying the H₂ electrodeusing various techniques, such as adsorption, bubbling with H₂, and N₂, charging,discharging, and recharging, replacing the salt bridge with a conducting wire, etc. Aninteresting overpotential was observed that bubbling H₂ into the solution caused a suddenchange of potential to more negative without changing the solution pH. The H₂ may bereplaced by N₂ to give a similar calibration curve without the overpotential. The resultscontradict the redox mechanism. When the Pt is separated by H₂ coating, it cannot act as acatalyst in the solution. Our results seem to explain the H₂ electrode mechanism as thecombination of its overpotential and capacitance potential. Bubbling of H₂ or N₂ onlyremoves interfering gases such as O₂ and CO₂. Since neither H₂ nor N₂ is involved in thepotential development, it is improper to call the H₂ or N₂ electrode. A term of pH / OH Ptelectrode, like the pH / OH glass electrode, is suggested.