Hydrogen has a low energy density
The reason that gasoline is so popular is that it is a liquid fuel which makes it easy to transport store and manipulate in a car. Also, a small volume of gasoline will hold a huge amount of energy.
The problems with hydrogen are:
-- Very difficult to transport. The atom is so small it leaks thru just about anything including solid metal (which it makes brittle).
-- Lower energy density than methane (which is easier to store and use in the car).
-- A danger in poorly ventilated areas. (e.g. underground parking garages filling up with hydrogen cars and fuel air explosive.)
-- Require platinum catalysts for the fuel cells. If these went into mass production the cost of platinum would go sky high. Furthermore, the catalysts are poisoned by impurities in the air so this very, very expensive part of the engine would have to be replaced regularly. After 20 years, we still have not found a cheap way to make long duration fuel cells.
-- The theft of platinum in car's fuel cells would be very economically viable.
-- Hydrogen is very expensive to produce with electrolysis and no service stations are built with the huge power lines and transformers to build the electricity on site. Cracking the hydrogen on site is uneconomical so no unsubsidized gas station owner will do this, even if there were some hydrogen cars on the road.
-- If hydrogen was transported to gas stations in tanker trucks, each of those big 18 wheeler sized tanks will fill up 20 cars, because hydrogen gas has such a low energy density.
-- Commercial hydrogen today is made from cracking methane (releasing CO2 into the air). This just adds to the greenhouse gas burden and converts the methane (which can be burnt now in natural gas cars) into a form that is more dangerous and less efficient.
-- Hydrogen needs heavy steel tanks (mass reduces range) or high tech carbon-carbon composites (explode during crashes). Both take up a huge amount of storage space. I ran a propane truck for a few years and lost a 1/3 of the truck's bed to the tank. And propane has a higher energy density than hydrogen.
Hydrogen cars are a total economic impossibility in several different respects. See the book "Energy Victory" by Dr. Robert Zubrin for more details why the 'hydrogen economy' is impossible.
We will need liquid fuels (such as gasoline or methanol) for the foreseeable future. Electric cars are a serious contender for people traveling a couple hundred km or less.
Warm regards, Rick.