Hydrogen gas has the potential to be a clean source of sustainable energy due to its high energy density. However, greenhouse gas emissions are still a major byproduct of current hydrogen production methods. Photoelectrochemistry provides a promising, environmentally friendly route to hydrogen production.However, the atomic scale mechanisms of the photocatalysts that facilitate the water splitting reaction are currently poorly understood. Further understanding of the chemical physics governing the active hydrogen evolution sites would allow for better design of photoelectrochemical devices and thus lead to improved reaction efficiencies. This will overcome one of the major barriers impeding this promising technology. We have developed a unique operando photoelectrochemistry transmission electronmicroscope liquid cell sample holder which can be used to characterize these reactions in real time at nanometer length scales. This system builds upon our prior developments of operando electrochemical liquid cell holders, by including the additional provision of an optical fiber directed at the sample to provide full solar spectrum illumination. In order to provide accurate, quantitative information, it is necessary to accurately deposit the photocatalyst of interest onto microfabricated electrodes. In this research, a precise sample deposition technique utilizing an inkjet printer has been developed along with stable suspensions of known photocatalysts, leading to site-specific deposition onto the electrode chips. Specifically, this experimental design allows for correlation between I-V characteristics and real time, high magnification imaging and spectroscopy, elucidating information about photocatalytic mechanisms at the nanoscale. The following photocatalysts used were chosen because the proposed mechanism for each exhibits a spatial dependence: plasmonically enhanced catalysis for Au nanoprisms and edges and wrinkles in two-dimensional MoS2 flakes. These experiments will lay the groundwork for the use of this novel experimental design to investigate a wide variety of photoelectrochemical systems and will allow determination of the mechanisms by which selected photocatalysts induce water splitting and the identification of defect features that serve as the active sites.

Development of a method to characterize active sites in photocatalysis using <i>operando</i> transmission electron microscopy

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

Development of a method to characterize active sites in photocatalysis using operando transmission electron microscopy