Hydrogen goop could be a more convenient fuel than hydrogen gas

ON PAPER, HYDROGEN looks like a dream fuel. Coal, oil and natural gas generate planet-warming carbon dioxide when burned. Hydrogen produces pure water. Hydrogen crams more energy into less space than batteries do (though, admittedly, less than petrol or diesel do). And an empty tank can be refilled with hydrogen much faster than an empty battery can be refilled with electricity.In practice, things are trickier. Storing meaningful quantities of hydrogen gas requires compressing it several hundred-fold. Liquefying it is another option, but one that requires cooling the stuff to -253°C. Either process requires rugged tanks. Over time, hydrogen gas can infiltrate metals, weakening them and potentially causing cracks. Tanks must be built from special materials designed to resist this breakdown.