If hydrogen fuel is the future, it has been for quite some time. In his 1875 novel The Mysterious Island, Jules Verne imagined the element replacing coal as a fuel, split out of water to “furnish an inexhaustible source of heat and light”. Similar noises were made in the 1970s oil crisis, when hydrogen was touted as an alternative fuel for cars. And then there was US president George W. Bush in 2003, latching on to a new enthusiasm for hydrogen vehicles during the first wave of real concern about climate change. “We can make a fundamental difference for the future of our children,” he said. Now hydrogen is back – again. From the US to Australia, and the European Union to China, the past year has seen an almost daily torrent of multibillion-dollar government funding pledges, tests of new technologies from trains and planes to domestic boilers, industry statements and analyses, and championing by leaders such as UK prime minister Boris Johnson. “We’re finding it hard to keep up wit...