What element is extracted from oil and natural gas?

Most of the hydrogen used by industry, as rocket fuel, and for fuel cell powered cars is extracted from oil and natural gas.

This actually makes the supposedly "clean" fuel cell powered car pretty much as polluting as ordinary cars (as far as carbon emissions are concerned). It would be much better if the hydrogen was extracted by electrolysis of water using electricity from nuclear power, hydroelectric, wind, etc. sources instead!