St. Louis Post-Dispatch: Not a sound escapes when the ignition is turned on. No carbon dioxide rolls from the exhaust — ever. Yet the inside and outside are no different than other vehicles on the road. Hydrogen fuel cell vehicles, such as General Motors Corp.’s retooled Equinox — displayed at the St. Louis Science Center last weekend — rely on a reaction between oxygen and stored hydrogen to create electricity. They are the future, automakers say. But when that future will arrive depends on whom …