@AC 10th March 2012 06:58 GMT:......Re: "yes but"
"How much energy does it take to produce the hardware, eg nano wires, then actually harvest the hydrogen?"
I was primarily thinking of the fascinating prospect that they might be able to produce short-chain hydrocarbons - hence my reference to basic solvents. If that became possible and even better the smaller hetero atom molecules then the effects could be very far-reaching indeed in the chemicals industry. The savings in energy consumption and pollution costs would be enormous and would, if the process were driven by sunlight, certainly repay the development, production and running costs. Just imagine if pentane, hexane, heptane and perhaps toluene (the simplest mono-substituted six-member aromatic ring) could be produced by this analogue of a biological system. Furthermore if the smaller hetero atomic molecules (ie containing at least one other atom other than carbon and hydrogen) were possible giving us (perhaps) the four smallest alcohols (methanol, ethanol, propanol and butanol) or perhaps even such solvents as tetrahydrafuran and dioxane then the effects would be utterly transformative. If such artificial sun-driven analogues of biological production systems became realizable the positive effects throughout industrial production on a world-wide basis would be so huge that it is not possible to do them justice in a small posting such as this.