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Published August 14, 2012 | Published + Supplemental Material
Journal Article Open

Imaging Water-Splitting Electrocatalysts with pH-Sensing Confocal Fluorescence Microscopy


Hydrogen generation by water electrolysis is promising for energy storage, and imaging the reaction dynamics near a H_2-evolving electrode can provide valuable insights. We utilized laser-scanning confocal fluorescence microscopy to map the product/reactant concentration at a H_2-evolving electrode at micron-scale resolution which identifies areas with fast reaction kinetics. Small concentrations of a pH indicator dye added to the aqueous electrolyte enables ratiometric fluorescence sensing for quantitative pH detection over the range pH 5.3-7.5 and minimally perturbs the local environment. To overcome diffusion limitations, a miniature flow cell was utilized in the microscope to achieve micron-scale resolution in steady state while applying galvanostatic current. We demonstrated the technique using F:SnO_2-coated glass with varied metal catalyst patterns and compositions resulting in clear images of increased pH near areas of high water-reducing activity. Simulations of the pH profiles near the electrolyte-patterned catalyst interface were also performed using the COMSOL finite-element software package to solve the convection/diffusion equations, and the calculation results agreed well with the experimentally-observed fluorescence profiles. Flow cell fluoresecence microscopy shows promise in imaging comparative catalyst activity as well as three-dimensional product/reactant profiles in complex electrode architectures.

Additional Information

© 2012 The Electrochemical Society. Manuscript submitted April 23, 2012; revised manuscript received June 19, 2012. Published August 14, 2012. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. We thank V. Ferry and J. McKone for helpful discussions. References

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Published - J._Electrochem._Soc.-2012-Leenheer-H752-7.pdf

Supplemental Material - 1370_1_video_24348_m5b247.mov


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September 14, 2023
October 23, 2023