el reacts electrochemically at one electrode and converts into protons and electrons. The protons move through the electrolyte to the other electrode, where they combine with oxygen from the air and with the electrons to form water, which is expelled from the cell as vapor. The involvement of hydrogen and oxygen in the two reactions--one releasing electrons and the other consuming them--yields electrical energy that is tapped across the electrodes for power, for example, to drive a motor. Hydrogen fuel cells are actually hydrogen batteries that generate electricity. Water electrolysis involves passing an electric current through H2O to separate it into hydrogen and oxygen. Hydrogen gas rises from the negative cathode and oxygen gas collects at the positive anode.Electrolysis produces extremely pure hydrogen, which is necessary for some types of fuel cells. But a significant amount of electricity is required to produce a usable amount of hydrogen from electrolysis. Ideally, this would come from renewable sources like wind and photovoltaics, and in the long term, it will. But hydrogen fuel promises little greenhouse gas mitigation if a developing hydrogen economy increases demand for
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