  Water splitting is unanimously recognized as environment friendly,
potentially low cost and renewable energy solution based on the future hydrogen
economy. Especially appealing is photo-catalytic water splitting whereby a
suitably chosen catalyst dramatically improves efficiency of the hydrogen
production driven by direct sunlight and allows it to happen even at zero
driving potential. Here, we suggest a new class of stable photo-catalysts and
the corresponding principle for catalytic water splitting in which infrared and
visible light play the main role in producing the photocurrent and hydrogen.
The new class of catalysts based on ionic binary metals with layered
graphite-like structures which effectively absorb visible and infrared light
facilitating the reaction of water splitting, suppress the inverse reaction of
ion recombination by separating ions due to internal electric fields existing
near alternating layers, provide the sites for ion trapping of both polarities,
and finally deliver the electrons and holes required to generate hydrogen and
oxygen gases. As an example, we demonstrate conversion efficiency of 27 percent
at bias voltage bias 0.5 V for magnesium di-boride working as a catalyst for
photo-induced water splitting. We discuss its advantages over some existing
materials and propose the underlying mechanism of photo-catalytic water
splitting by binary layered metals.
