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Hydrogen evolution reaction (HER) is a chemical reaction that yields H 2. [1] The conversion of protons to H 2 requires reducing equivalents and usually a catalyst. In nature, HER is catalyzed by hydrogenase enzymes. Commercial electrolyzers typically employ supported platinum as the catalyst at the anode of the electrolyzer.
The catalytic performance of Mo3P nanoparticles is tested in the hydrogen evolution reaction (HER), indicating an onset potential of as low as 21 mV, H2 formation rate, and exchange current density of 214.7 μmol/(s·g) cat (at only 100 mV overpotential) and 279.07 μA/cm 2, respectively, which are among the closest values yet observed to platinum.
For example, hydrogen is oxidized and protons are reduced readily at the platinum surface of a standard hydrogen electrode in aqueous solution, in a Hydrogen Evolution Reaction. Substituting an electrocatalytically inert glassy carbon electrode for the platinum electrode produces irreversible reduction and oxidation peaks with large overpotentials.
The values below are standard apparent reduction potentials (E°') for electro-biochemical half-reactions measured at 25 °C, 1 atmosphere and a pH of 7 in aqueous solution. [1] [2] The actual physiological potential depends on the ratio of the reduced (Red) and oxidized (Ox) forms according to the Nernst equation and the thermal voltage.
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 ...
The redox potentials for these reactions are similar to that for hydrogen evolution in aqueous electrolytes, thus electrochemical reduction of CO 2 is usually competitive with hydrogen evolution reaction. [2] Electrochemical methods have gained significant attention: at ambient pressure and room temperature;
However, the total cell potential (difference between oxidation and reduction half cell potentials) will remain 1.23 V. This potential can be related to Gibbs free energy (ΔG) by: ΔG°cell = −nFE°cell Where n is the number of electrons per mole products and F is the Faraday constant. Therefore, it takes 475 kJ of energy to make one mole of ...
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