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Solar Fuels group breakthrough with water oxidation catalyst

Acid-based electrolysis has many advantages, but to achieve simultaneous activity and stability, commercial Q3 water oxidation catalysts rely on noble metal oxides that are expensive and too rare for the global scale.

The University of Louisville Conn Center’s Solar Fuels group has published a recent breakthrough in the journal of Energy and Environmental Science that will make the production of water splitting catalysts faster and cheaper.

Authors Joshua Spurgeon, research engineer, and Sudesh Kumari, postdoctoral fellow, are trying to make improved catalysts that help to break down water into hydrogen and oxygen through electrochemistry. For this, a water oxidation catalyst is necessary, which is a material surface on which it is easier to break the bonds of a water molecule. This is important for a process like electrolysis, or water splitting, to run efficiently.

Unfortunately, the acidic conditions where electrolysis is most effective are also very harsh and most materials do not survive as catalysts because they corrode. Only rare metal oxide materials are stable under these conditions and this leads to issues with the cost and scalability for an electrolyzer.

In this work, they have made alloy materials as catalysts for water splitting that use mostly an abundant metal (tungsten) and only a small amount of rare metal (iridium), while still having an effective catalyst that resists corrosion in an electrolyzer. To work effectively, this material was made in a novel fabrication method through synthesis in a plasma. Standard thermal processing for the same material led to a much less effective catalyst.

Patrick Ajayi treats a sample using rapid plasma oxidation.

Water-splitting to make hydrogen is a promising route to produce clean fuels that can displace traditional fossil fuels. Water electrolysis to hydrogen is also an effective way to store renewable electricity such as solar and wind energy so that it can be used even when the sun is not shining or the wind is not blowing. To make water electrolysis a competitive technology, effective catalysts which are cheap, abundant, and stable are needed.

This work shows effective catalysis for water-splitting in acidic conditions, with some of the lowest rare metal content yet reported. Also, the novel plasma synthesis technique used in the work was necessary to produce the more effective catalyst. This method could thus lead to improvements in other material systems that rely on an alloy composition.

The reported catalyst used far less rare metal than current state of the art. The work also demonstrates the benefit of the plasma synthesis method, which leads to a different phase of the mixed-metal alloy material than produced through typical high-temperature processing.

Catalyst sample treated by rapid plasma oxidation

The catalysts have the potential to make hydrogen generation from water more affordable. Clean hydrogen fuel only gives water back again when it is burned, and is pollution-free. It is also a promising way to store excess solar and wind electricity for use at other times and in other locations.

The manuscript, titled A Low-noble-metal W1-xIrxO3-δ Water Oxidation Electrocatalyst for Acidic Media via Rapid Plasma Synthesis is by authors Sudesh Kumari, Patrick Ajayi, Bijandra Kumar, Jacek Jasinski, Mahendra Sunkara, and Joshua Spurgeon, and appears in the journal Energy and Environmental Science.

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