I think your assumption that 1 oz. of platinum would be required to process 100 kg of sugar is way off. Nevertheless, all this talk about hydrogen-powered cars is a bunch of hooey.
Actually, I said 1000 kg of sugar. Rather a bit more, true?
I don't for a moment think that H2 power is all 'hooey', but it's WAAAY overhyped until certain technical developments occur.