 There are more than 200 thermochemical cycles which can be used for water splitting , around a dozen of these cycles such as the iron oxide cycle , cerium ( IV ) oxide – cerium ( III ) oxide cycle , zinc zinc @-@ oxide cycle , sulfur @-@ iodine cycle , copper @-@ chlorine cycle and hybrid sulfur cycle are under research and in testing phase to produce hydrogen and oxygen from water and heat without using electricity . A number of laboratories ( including in France , Germany , Greece , Japan , and the USA ) are developing thermochemical methods to produce hydrogen from solar energy and water . 
