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As far as having leftover carbon if hydrocarbon is used as the feed stock, is this not true of crude oil too? Only a small portion of the crude is made into gasoline, diesel or other light fuels, .. misleading comment at best, it really *is* different ... most of the energy in a barrel of crude goes to useful oil grades. but the method used to create hydrogen - methane reformation - takes already processed natural gas and in an expensive and energy inefficient way converts it into hydrogen. This is the LEAST expensive method - hydrolysis etc., costs more.

It is more efficient to take natural gas and use it in an efficient ICE car, than to convert it to hydrogen for a fuel cell car.

Fuel cells have the additional advantage of being a non-thermodynamic process, and not subject to the same "rules", so the higher effeciencies are *theoretically* possible. dont imply that thermodynamics is repealed. The PEM cell efficiencies have limits too, around 50%, based on the voltage gaps and current flow - decent current flow forces lower efficiency.

whatever theoretic efficiencies, the REAL fuel efficiencies of fuel cell cars is not better than the best hybrid technology (~40% engine+ drivetrain efficiency). Car cost differentials FAR OUTWEIGH the minor cost differentials of different fuel efficiencies.