Solar energy can be stored by converting it into hydrogen, but current methods are too expensive and don’t last long. Using commercially available solar cells and none of the usual rare metals, researchers at EPFL and CSEM have now designed a device that outperforms in stability, efficiency and cost.   How can we store solar energy for period when the sun doesn’t shine? One solution is to convert it into hydrogen through water electrolysis. The idea is to use the electrical current produced by...