PowerSwitch

Scientists at the University of East Anglia, led by Dr. Thomas Nann, report a breakthrough in the production of hydrogen from water using the energy of sunlight.
They report 60% efficiency for a process in which hydrogen is produced from water by the photons in light that strike a specially designed submersed electrode.

The trick lies in the nanophotocathode used by Nann's team. A gold electrode coated with nanoclusters of indium phosphide absorb incoming photons of light (that is the wavy line marked "hv" in the image). The nanoclusters then pass electrons liberated by the sun's energy into an iron-sulfur complex which acts like a match-maker between the negatively charged electron and a hydrogen proton in the surrounding water molecules. Gaseous hydrogen results.

Indium ranks 61st in abundance in the Earth's crust at approximately 0.25 ppm,[7] which means it is more than three times as abundant as silver, which occurs at 0.075 ppm.[8] Fewer than 10 indium minerals are known, none occurring in significant deposits. Examples are the dzhalindite (In(OH)3) and indite (FeIn2S4).[9]

Resources

Based on content of indium in zinc ore stocks, there is a worldwide reserve base of approximately 6,000 tonnes of economically viable indium.[10] This figure has led to estimates suggesting that, at current consumption rates, there is only 13 years' supply of indium left.[11] However, the Indium Corporation, the largest processor of indium, claims that, on the basis of increasing recovery yields during extraction, recovery from a wider range of base metals (including tin, copper and other polymetallic deposits) and new mining investments, the long-term supply of indium is sustainable, reliable and sufficient to meet increasing future demands.[12]

This conclusion also seems reasonable in light of the fact that silver, three times less abundant than indium in the earths crust,[13] is currently mined at approximately 18,300 tonnes per annum,[14] which is 40 times greater than current indium mining rates.