Catalysis

Boosting efficiency in light-driven water splitting by dynamic irradiation through synchronizing reaction and transport processes

Authors

Abstract

This work elaborates the effect of dynamic irradiation on light-driven molecular water oxidation to counteract catalyst deactivation. It highlights the importance of overall reaction engineering to overcome limiting factors in artificial photosynthesis reactions. Systematic investigation of a homogenous three component ruthenium-based water oxidation system revealed significant potential to enhance the overall catalytic efficiency by synchronizing the timescales of photoreaction and mass transport in a capillary flow reactor. The overall activity could be improved by a factor of more than 10 with respect to the turnover number and a factor of 31 referring to the external energy efficiency by controlling the local availability of photons. Detailed insights into the mechanism of light driven water oxidation could be obtained using complementary methods of investigation like Raman, IR and UV-vis/emission spectroscopy, unraveling the importance of avoiding high concentrations of excited photosensitizers.

Version notes

The revised version was extended by comprehensive studies on the degradation of the photosensitizer. For this, additional spectroscopic studies, including UV/vis, Raman and IR spectroscopy, were conducted. These results clearly show that the degradation of the photosensitizer is the main cause for activity loss. Furthermore, it could be concluded that the degradation is accelerated by high light intensities that cause a high local concentration of sulfate radicals that oxidize the photosensitizer. With this, the working hypothesis that temporal changes of the irradiation intensities lead to long activity could be further strengthened and the link to mass transport effects became clearer. The manuscript was thoroughly revised to reflect these new insights.

Content

Thumbnail image of WOC-reaction-optimisation.pdf

Supplementary material

Thumbnail image of WOC-reaction-optimisation_SI.pdf
Supporting Information to "Boosting efficiency in light-driven water splitting by dynamic irradiation through synchronizing reaction and transport processes"
Describes reaction conditions, reactor setup, analysis methods, way of evaluation of measured catalytic performance and theoretical considerations for the contribution "Boosting efficiency in light-driven water splitting by synchronizing reaction and transport processes through dynamic irradiation"
Thumbnail image of ESI-movie_2.mp4
Video: Mixing with custom made stirring bar
A video that shows how intense mixing of the liquid is achieved using the 3d-printed stirring bar described in the manuscript.
Thumbnail image of ESI-movie_2.mp4
Video: Mixing with standard stirrbar
A video that shows that the use of a standard stirring bar leads to less efficient mixing of the liquid.