Abstract
Water splitting is unanimously recognized as environment friendly, potentially low cost and renewable energy solution based on the future hydrogen economy. Especially appealing is photocatalytic 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 photocatalysts 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 - ionic or covalent binary metals with layered graphite-like structures - 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% at bias voltage Vbias = 0.5V for magnesium diboride working as a catalyst for photoinduced water splitting. We discuss its advantages over some existing materials and propose the underlying mechanism of photocatalytic water splitting by binary layered metals.
Highlights
The decomposition of water by sunlight has long been recognized as a potentially important reaction to harvest and store solar energy for two main reasons
The photocatalytic water splitting makes use of semiconducting, dielectric and so-called metal free materials which demonstrate the mentioned shortcomings. (In parenthesis we note that recently there are some reports on using metals in various complex compounds.) We try to go in a different direction: our photocalytic method is based on earth abundant metals which possess a very high concentration of conduction electrons
We show that the electrodes produced from MgB2 by a simple spraying process can demonstrate photocatalytic water splitting with high solar energy conversion efficiency
Summary
The decomposition of water by sunlight has long been recognized as a potentially important reaction to harvest and store solar energy for two main reasons. It is safe to say that the abundant, stable and effective photocatalyst for water splitting is still lacking and the water splitting technology does not utilise the whole range of solar light capable of producing the reaction [2,14] To break through these restrictions, a new mechanism and materials are needed. (In parenthesis we note that recently there are some reports on using metals in various complex compounds.) We try to go in a different direction: our photocalytic method is based on earth abundant metals which possess a very high concentration of conduction electrons These materials can absorb light from broad spectral region (IR and VS) and a huge number of electrons take part in photocatalysts processes resulting in photocurrent enhancement. Such visibleinfrared-light-driven water splitting opens a new future for solar energy conversion
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