Residual heat to produce Hydrogen: it's all about low temperatures
Hydrogen could be a nice solution for many of our current problems with fossil fuels: it provides dense, portable energy without producing harmful emissions when burnt. The difficulty, of course, is in producing large amounts of hydrogen without wasting more energy than it's worth. Caltech's Mark E. Davis is working on this problem, and he sees the solution in harvesting excess heat from various other industrial processes. Simple one-step chemical reactions that split water into its two components require very high temperatures, upwards of 1000C. Impractical for most situations. Davis' team has demonstrated a four-step chemical cycle that can repeatedly produce hydrogen and oxygen from water at lower temperatures: only about 850C. Though they showed that the cycle can be repeated five times, this is still far from the thousands of cycles needed to make the process industrially feasible.
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