The belief that solar energy harnessed by photochemical processes may be able, in the future, to make a worthwhile contribution to the energy requirements of the world is supported by many of the results being reported by a growing number of workers in this rapidly expanding field of research.

The present interest in the production of hydrogen and oxygen by the visible-light photolysis of water was highlighted in a recent review of The Third International Conference on Photochemical Conversion and Storage of Solar Energy, by Professor Sir George Porter, F.R.S. whose group at The Royal Institution, London, is actively engaged in this area (Nature (London), 1980, 288, (5789), 320–321).

Platinum and ruthenium dioxide are known to be electrolytically active for the evolution of hydrogen and oxygen, respectively, and Professor Michael Grätzel and colleagues at the Institute of Physical Chemistry, Lausanne reported the decomposition of water using these two catalysts, together with ruthenium trisbipyridyl as the light sensitiser and methyl viologen as the carrier, in a single system without sacrificial electron donors or acceptors.