Steering molecular twisting for hydrogen generation
Researchers from the Faculty of S&T at the University of Twente have developed a novel approach for the design of efficient solar fuel devices. Research performed by graduated Ph.D. student Kaijian Zhu shows that reducing the light-induced twisting of molecules can turn hydrogen generation on. The study is published in Advanced Science.
Photoelectrochemical cells are promising for the production of solar fuels, for example, the conversion of water into hydrogen or CO2 into organic molecules. However, their efficiency has been limited by the performance of the photocathode, one of the functional electrodes in these cells. Present research focuses on manipulating the behavior of molecules on the nickel oxide (NiO) surfaces of these photocathodes.
When light is absorbed by the dye molecules on the NiO surface, they twist to promote the separation of positive and negative charges. A key question is how this twisting affects the performance of the photocathode. Zhu’s research has demonstrated that by reducing this twisting process, hydrogen generation under illumination can be turned on.
By adding a long chain, hydrophobic hydrocarbon (myristic acid) to the NiO surface next to the light-sensitive dye molecules, the researchers were able to control and reduce the degree of twisting of the dye molecules when light is absorbed. Interestingly, the presence of myristic acid enabled light-induced hydrogen evolution in water even without a hydrogen evolution catalyst.
Annemarie Huijser, says the corresponding author of this work
“The hydrogen generation is likely a synergetic effect of inhibited twisting of the dye radical anion, increasing its electrochemical potential, combined with charge transfer and reduction of protons at the hydroxylated NiO surface,”
The research illustrates the importance of understanding the effects of light-induced intramolecular twisting and demonstrates that control of the process enables a straightforward design approach for efficient photocatalysis.
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Steering molecular twisting for hydrogen generation, source
