Oxidation catalysts for sunlight driven H2 fuel production.
- Faster reactivity compared to previously disclosed water oxidation catalysts (WOCs).
- Hydrolytic stability exceeds that observed for earlier catalysts.
- Easily prepared from readily available materials.
Hydrogen fuel is currently considered a potential replacement for today's fossil fuels due to its abundance and efficiency. Additionally, it produces no emissions and offers the potential to be renewable. If hydrogen were to replace oil, the demand would equal ~40% of the total energy demand in the U.S. The development of effective, stable and selective WOCs is highly important for the production of alternative fuels such as hydrogen and other carbon neutral fuels. While heterogeneous catalysts have shown greater stability than homogeneous catalysts, they are also more difficult to optimize, tend to deactivate by surface poisoning or aggregation, and are typically slower than homogeneous catalysts. Additionally, many of the homogeneous catalysts have organic ligands which are thermodynamically unstable and susceptible to oxidation in air or the presence of oxygen.
The WOC developed at Emory is a homogeneous catalyst which has the combined advantages of the homogenous and heterogeneous catalyst systems. Our homogeneous WOC contains vanadate(V)-centered polyoxometalate ligands and all earth-abundant metals. This new water oxidation catalyst oxidizes water very rapidly, remains highly stable, and is easy to prepare with readily available materials. Prior catalysts have lacked practicality in terms of selectivity, speed, and stability, but this catalyst overcomes these obstacles. For example, the distinct electronic structure has led to reactant turn-over rates 5 times faster than previously disclosed WOCs. The water oxidation reaction shows a turnover frequency of approximately 4.8 x 103 in less than three minutes once the catalyst is applied. Increased hydrolytic stability compared to previous catalysts is also observed. This potent WOC is central to the transformation of water and sunlight to hydrogen fuel.
Proof-of-principle catalyst production and light driven reactions have been completed.