Abstract: A catalyst for the photo-electrolysis of water molecules, the catalyst including catalytic groups comprising tetra-manganese-oxo clusters. A plurality of the catalytic groups are supported on a conductive support substrate capable of incorporating water molecules. At least some of the catalytic groups, supported by the support substrate, are able to catalytically interact with water molecules incorporated into the support substrate. The catalyst can be used as part of photo-electrochemical cell for the generation of electrical energy.