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The electrode is immersed in the acidic solution and pure hydrogen gas is bubbled over its surface. The concentration of both the reduced and oxidised forms of hydrogen are maintained at unity. That implies that the pressure of hydrogen gas is 1 bar (100 kPa) and the activity coefficient of hydrogen ions in the solution is unity.
Unlike the standard hydrogen electrode, its measured potential does change with the pH, so it can be directly used in the electrolyte. [1] [2] [3] The name refers to the fact that the electrode is directly immersed in the actual electrolyte solution and not separated by a salt bridge. The hydrogen ion concentration is therefore not 1 mol/L, or ...
For pure water (pH 7): the electrode potential for the reduction producing hydrogen is −0.41 V, the electrode potential for the oxidation producing oxygen is +0.82 V. Comparable figures calculated in a similar way, for 1 M zinc bromide, ZnBr 2, are −0.76 V for the reduction to Zn metal and +1.10 V for the oxidation producing bromine.
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
Faradaic losses describe the efficiency losses that are correlated to the current, that is supplied without leading to hydrogen at the cathodic gas outlet. The produced hydrogen and oxygen can permeate across the membrane, referred to as crossover. [15] Mixtures of both gases at the electrodes result. At the cathode, oxygen can be catalytically ...
The vertical scale is the electrode potential of hydrogen or non-interacting electrode relative to an SHE electrode, the horizontal scale is the pH of the electrolyte (otherwise non-interacting). Neglecting overpotential , above the top line the equilibrium condition is oxygen gas, and oxygen will bubble off of the electrode until equilibrium ...
A standard half-cell consists of a metal electrode in an aqueous solution where the concentration of the metal ions is 1 molar (1 mol/L) at 298 kelvins (25 °C). [1] In the case of the standard hydrogen electrode (SHE) , a platinum electrode is used and is immersed in an acidic solution where the concentration of hydrogen ions is 1M, with ...
In electrochemistry, electrode potential is the voltage of a galvanic cell built from a standard reference electrode and another electrode to be characterized. [1] By convention, the reference electrode is the standard hydrogen electrode (SHE). It is defined to have a potential of zero volts. It may also be defined as the potential difference ...