Electrolysis of water to produce green hydrogen is a process that involves the use of expensive ‘noble’ materials, such as platinum and palladium, as catalysts (substances that speed up a chemical reaction without being consumed in the process), making the hydrogen more expensive. The search is on for cheaper catalysts.
Researchers are onto materials called ‘molecular catalysts’, where molecules exist discretely, individually. These molecular structures typically have a central metal atom surrounded by ligands, or other molecules such as chlorine and ammonia that attach themselves to the metal.
A team from IIT-Bombay’s Department of Chemistry, led by Prof Arnab Dutta, explored the use of a molecular catalyst called cobaloxime for use in electrolysers, in place of expensive noble metals. It is water-soluble and stable in air, making it easier to handle than noble metals.
Strategic application of this cobalt-based catalyst can make hydrogen production efficient and cost-effective, say the researchers, in a paper published in Energy and Climate Change.
While the use of cobaloxime as a catalyst in electrolysers is not new, modifications to the molecular structure of cobaloxime have improved its stability and reaction rate. The IIT-Bombay team introduced natural amino acids, vitamins, and other functional groups to increase hydrogen production while maintaining energy efficiency. They have also modified cobaloximes to work in different water conditions, including seawater.
Industrial use
A report based on the paper, available on the IIT-B website, notes that while cobaloximes are a lot cheaper than noble metals and can be synthesised easily, there is also a flip side. “Cobaloximes work well in labs, but it is complex to use them for industrial hydrogen production,” notes Dutta.
The objective, therefore, is to modify their structure to make them compatible with the electrodes of the electrolyser and attach them to solid supports to enhance stability, efficiency, and durability. The ongoing research is to help make cobaloximes work better in an industrial setting.
Dutta’s team has found that cobaloxime catalysts perform well in both alkaline electrolysers, which use solutions like potassium hydroxide, as well as proton exchange membrane electrolysers, which use a solid polymer membrane in acidic conditions.
“We are currently developing the updated version of the cobaloxime template that can be used in heterogeneous conditions, applicable in an industrial setup,” Dutta told Quantum.
The paper notes that it is critical to bring down the cost of green hydrogen — hydrogen produced by electrolysers powered by renewable energy — especially to produce the in-demand green steel, namely steel produced using green hydrogen instead of coal (coke).