Organic polymer dots boost green hydrogen production

Scientists at Sweden’s Uppsala University have developed a new type of polymer dot photocatalyst that enhances the production of green hydrogen.

polymer dots
The polymer dots in the black solution (inset image) can absorb more light, and show better photocatalytic properties, than the single-component polymer dots in the coloured solutions (Credit: P-Cat)

Photocatalysts can separate the hydrogen and oxygen components in water using sunlight, resulting in green hydrogen which can then be integrated into the energy system as a renewable power source.

Until now, these photocatalysts have generally been derived from metals, which can be expensive and in many cases toxic, jeopardising the technology’s green credentials.

The nano-sized organic polymer dots – or Pdots – developed by the team at Uppsala are designed to be environmentally friendly and cost-effective, merging three different light-absorbing components to boost the efficiency of the photocatalytic reaction.

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“Combining several components that absorb light at different wavelengths is the easiest way to create a system in which all the visible surfaces capture light,” said lead researcher Haining Tian, Associate Professor of Physical Chemistry at Uppsala University.

“But getting these components to work well together in a photocatalytic system is challenging.”

To investigate how well the three components worked together, Tian and his colleagues used spectroscopic techniques in which the Pdot was exposed to light for a certain length of time. They were then able to follow how photochemical intermediates were created and, under illumination, disappeared.

The team optimised the triple-component polymer dots so that they catalyse the conversion of solar energy into hydrogen with a seven per cent efficiency rate at 600 nanometres (nm). This was a significant improvement on the 0.3 per cent at 600nm obtained by the group when they were working on Pdots consisting of just a single component. The work is published in the Journal of the American Chemical Society.

“It’s exciting to see that both ultrafast energy transfer and electron transfer take place in one particle, and that this helps the system to make use of the light and separate the charge for the catalytic process,” said study lead author Aijie Liu, a postdoctoral researcher at Uppsala’s Department of Chemistry – Ångström Laboratory.