Why can we not build a fuel cell that uses petrol or alcohol?

Question

We already utilise a fuel cell in breath analysis technology,

It would seem to get away from the production and safety issues of Hydrogen gas

Answer 1

You can indeed do this.  It is actually a two step process.  First the hydrogen must be released from the hydrocarbon or alcohol, and next the hydrogen is combined oxygen in the air to generate electricity across a catalytic membrane.

Answer 2

We haven't changed to it because of money. Money in the pockets of all the manufacturers getting kick backs and what not to use gasoline.

These billionaires will fight tooth and nail to keep from changing to a fuel that's cheap, plentiful and environmentally safe.

Money, money, money.

Answer 3

It can be done, but it is expensive. Such a fuel cell big enough to power a car is very expensive and the cars would cost way more than people would be willing to pay.

Answer 4

Two reasons.  One has already been mentioned.  Money.

The other is that the car would then produce CO2 out the back end, and would still take petrol in the tank.  

One beautiful thing about hydrogen-based cars, from the perspective of marketing them, is that you can honestly tell the public that they are buying a car where the only emission is water.  People get excited about that - and thus are willing to pay some extra money (and put up with some limitations on where you could get fuel) for that car..    

People would get much less excited if what they were told is that they were paying a premium for a car that still took fossils fuels (just much less of them) and still emitted CO2 (just much less of it.)

At least, that's my take on it.