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Half reactions are often used as a method of balancing redox reactions. For oxidation-reduction reactions in acidic conditions, after balancing the atoms and oxidation numbers, one will need to add H + ions to balance the hydrogen ions in the half reaction.
The hydrogen electrode is based on the redox half cell corresponding to the reduction of two hydrated protons, 2H + (aq), into one gaseous hydrogen molecule, H 2(g).. General equation for a reduction reaction:
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
Efficiency of modern hydrogen generators is measured by energy consumed per standard volume of hydrogen (MJ/m 3), assuming standard temperature and pressure of the H 2. The lower the energy used by a generator, the higher its efficiency would be; a 100%-efficient electrolyser would consume 39.4 kilowatt-hours per kilogram (142 MJ/kg) (higher ...
The half reaction taking place on the cathode side of a PEM electrolyzer is commonly referred to as the Hydrogen Evolution Reaction (HER). Here the supplied electrons and the protons that have conducted through the membrane are combined to create gaseous hydrogen.
In electrochemistry, the Nernst equation is a chemical thermodynamical relationship that permits the calculation of the reduction potential of a reaction (half-cell or full cell reaction) from the standard electrode potential, absolute temperature, the number of electrons involved in the redox reaction, and activities (often approximated by concentrations) of the chemical species undergoing ...
Since hydrogen can be used as an alternative clean burning fuel, there has been a need to split water efficiently. However, there are known materials that can mediate the reduction step efficiently therefore much of the current research is aimed at the oxidation half reaction also known as the Oxygen Evolution Reaction (OER).
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 ...