Rice University scientists have created an efficient, simple-to-manufacture oxygen-evolution catalyst that pairs well with semiconductors for solar water splitting, the conversion of solar energy to chemical energy in the form of hydrogen and oxygen.
The lab of Kenton Whitmire, a Rice professor of chemistry, teamed up with researchers at the University of Houston and discovered that growing a layer of an active catalyst directly on the surface of a light-absorbing nanorod array produced an artificial photosynthesis material that could split water at the full theoretical potential of the light-absorbing semiconductor with sunlight.
An oxygen-evolution catalyst splits water into hydrogen and oxygen. Finding a clean renewable source of hydrogen fuel is the focus of extensive research, but the technology has not yet been commercialized.
The Rice team came up with a way to combine three of the most abundant metals — iron, manganese and phosphorus — into a precursor that can be deposited directly onto any substrate without damaging it.
To demonstrate the material, the lab placed the precursor into its custom chemical vapor deposition (CVD) furnace and used it to coat an array of light-absorbing, semiconducting titanium dioxide nanorods. The combined material, called a photoanode, showed excellent stability while reaching a current density of 10 milliamps per square centimeter, the researchers reported.
The results appear in two new studies. The first, on the creation of the films, appears in Chemistry: A European Journal. The second, which details the creation of photoanodes, appears in ACS Nano.
Whitmire said the catalyst is grown from a molecular precursor designed to produce it upon decomposition, and the process is scalable. The Rice lab combined iron, manganese and phosphorus (FeMnP) into a molecule that converts to a gas when vacuum is applied. When this gas encounters a hot surface via CVD, it decomposes to coat a surface with the FeMnP catalyst.