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Standard hydrogen electrode scheme: 1) Platinized platinum electrode, 2) Hydrogen gas, 3) Acid solution with an activity of H + = 1 mol/L, 4) Hydroseal for prevention of oxygen interference, 5) Reservoir via which the second half-element of the galvanic cell should be attached.
During the early development of electrochemistry, researchers used the normal hydrogen electrode as their standard for zero potential. This was convenient because it could actually be constructed by "[immersing] a platinum electrode into a solution of 1 N strong acid and [bubbling] hydrogen gas through the solution at about 1 atm pressure".
The data below tabulates standard electrode potentials (E°), in volts relative to the standard hydrogen electrode (SHE), at: Temperature 298.15 K (25.00 °C; 77.00 °F); Effective concentration (activity) 1 mol/L for each aqueous or amalgamated (mercury-alloyed) species; Unit activity for each solvent and pure solid or liquid species; and
A platinum electrode is placed inside the bottom of each of the two side cylinders, connected to the positive and negative terminals of a source of electricity. When current is run through Hofmann's voltameter, gaseous oxygen forms at the anode and gaseous hydrogen at the cathode. Each gas displaces water and collects at the top of the two ...
The time that takes the electrode to establish equilibrium with the solution will affect the sensitivity or accuracy of the measurement. In aquatic environments, platinum is often used due to its high electron transfer kinetics, [5] although an electrode made from several metals can be used in order to enhance the electron transfer kinetics. [6]
The hydrogen atoms occupy interstitial sites in palladium hydride. The H–H bond in H 2 is cleaved. The ratio in which H is absorbed on Pd is defined by = [] [].When Pd is brought into a H 2 environment with a pressure of 1 atm, the resulting concentration of H reaches x ≈ 0.7.
The palladium-hydrogen electrode (abbreviation: Pd/H 2) is one of the common reference electrodes used in electrochemical study. [1] Most of its characteristics are similar to the standard hydrogen electrode (with platinum). But palladium has one significant feature—the capability to absorb (dissolve into itself) molecular hydrogen. [2] [3]
The standard hydrogen electrode (SHE), with [ H +] = 1 M works thus at a pH = 0. At pH = 7, when [ H +] = 10 −7 M, the reduction potential of H + differs from zero because it depends on pH. Solving the Nernst equation for the half-reaction of reduction of two protons into hydrogen gas gives: 2 H + + 2 e − ⇌ H 2