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Electrolysis of water is the decomposition of water (H 2 O) into oxygen (O 2) and hydrogen (H 2): [2] Water electrolysis ship Hydrogen Challenger. Production of hydrogen from water is energy intensive. Usually, the electricity consumed is more valuable than the hydrogen produced, so this method has not been widely used.
Considering the industrial production of hydrogen, and using current best processes for water electrolysis (PEM or alkaline electrolysis) which have an effective electrical efficiency of 70–80%, [68] [73] [74] producing 1 kg of hydrogen (which has a specific energy of 143 MJ/kg) requires 50–55 kW⋅h (180–200 MJ) of electricity.
High-pressure electrolysis is being investigated by the DOE for efficient production of hydrogen from water. The target total in 2005 is $4.75 per gge H 2 at an efficiency of 64%. [10] The total goal for the DOE in 2010 is $2.85 per gge H 2 at an efficiency of 75%. [11] As of 2005 the DOE provided a total of $1,563,882 worth of funding for ...
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 reacted with hydrogen on the platinum surface of the cathodic catalyst. At the anode, hydrogen and oxygen do not react at the iridium oxide catalyst. [15]
High pressure electrolysis is the electrolysis of water by decomposition of water (H 2 O) into oxygen (O 2) and hydrogen gas (H 2) by means of an electric current being passed through the water. The difference with a standard electrolyzer is the compressed hydrogen output around 120–200 bar (1740–2900 psi , 12–20 MPa ). [ 146 ]
Hydrogen can be purified by passing through a membrane composed of palladium and silver. Permeability of the former to hydrogen was discovered back in the 1860s. [2] An alloy with a ca. 3:1 ratio for Pd:Ag is more structural robust than pure Pd, which is the active component that allows the selective diffusion of H 2 through it.