Nanocoatings improve water-splitting efficiency

Researchers have shown that a specialised coating technique can make water-splitting devices more stable and more efficient, a development made possible with atomic layer deposition that could advance carbon-neutral fuels.

Splitting water into its components is an important first step in achieving carbon-neutral fuels to power transportation infrastructure, including cars and aircraft.

The research, from North Carolina State University and the University of North Carolina at Chapel Hill, are published in two separate papers in the Proceedings of the National Academy of Sciences.

Atomic layer deposition (ALD) coats three-dimensional structures with a precise, ultra-thin layer of material.

‘In this case, the layers are less than one nanometre thick – or almost a million times thinner than a human hair,’ said Dr Mark Losego, research assistant professor of chemical and biomolecular engineering at NC State and a co-author on the work.

Although extremely thin, these coatings improve the attachment and performance of surface-bound molecular catalysts used for water-splitting reactions in hydrogen-fuel-producing devices.

In the first paper, ‘Solar water splitting in a molecular photoelectrochemical cell,’ the researchers used ALD coatings on nanostructured water-splitting cells to improve the efficiency of electrical current flow from the molecular catalyst to the device. The findings are claimed to have significantly improved the hydrogen generating capacity of these molecular-based solar water-splitting cells.

In the second paper, ‘Crossing the divide between homogeneous and heterogeneous catalysis in water oxidation,’ the researchers used ALD to ‘glue’ molecular catalysts to the surface of water-splitting electrodes in order to make them more impervious to detachment in non-acidic water solutions.

This improved stability at high pH enabled a new chemical pathway to water splitting that is one million times faster than the route that had been previously identified in acidic, or low pH, environments.

These findings could have implications in stabilising a number of other molecular catalysts for other renewable energy pathways, including the conversion of carbon dioxide to hydrocarbon fuels.

‘In these reports, we’ve shown that nanoscale coatings applied by ALD can serve multiple purposes in water-splitting technology, including increasing hydrogen production efficiency and extending device lifetimes,’ Losego said in a statement. ‘In the future, we would like to build devices that integrate both of these advantages and move us toward other fuels of interest, including methanol production.’