The H
2 electrode is commonly assumed to be a half-cell, 2 H
+ 2e == H
2, andexplained by the Nernst equation. We cannot assume that the H
+ is easily reduced to H
2 inan H
2 saturated solution, and H
2 becoming oxidized to H
+ in a strongly acid solution againstthe equilibrium principle. How can the H
2 gas is involved from a basic solution where thereis 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 electrodeusing 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. Aninteresting overpotential was observed that bubbling H
2 into the solution caused a suddenchange of potential to more negative without changing the solution pH. The H
2 may bereplaced by N
2 to give a similar calibration curve without the overpotential. The resultscontradict the redox mechanism. When the Pt is separated by H
2 coating, it cannot act as acatalyst in the solution. Our results seem to explain the H
2 electrode mechanism as thecombination of its overpotential and capacitance potential. Bubbling of H
2 or N
2 onlyremoves interfering gases such as O
2 and CO
2. Since neither H
2 nor N
2 is involved in thepotential development, it is improper to call the H
2 or N
2 electrode. A term of pH / OH Ptelectrode, like the pH / OH glass electrode, is suggested.
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