In Situ Transmission Electron Microscopy of Electrocatalyst Materials: Proposed Workflows, Technical Advances, Challenges, and Lessons Learned.

In situ electrochemical liquid phase transmission electron microscopy (LP-TEM) measurements utilize micro-chip three-electrode cells with electron transparent silicon nitride windows that confine the liquid electrolyte. By imaging electrocatalysts deposited on micro-patterned electrodes, LP-TEM provides insight into morphological, phase structure, and compositional changes within electrocatalyst materials under electrochemical reaction conditions, which have practical implications on activity, selectivity, and durability. Despite LP-TEM capabilities becoming more accessible, in situ measurements under electrochemical reaction conditions remain non-trivial, with challenges including electron beam interactions with the electrolyte and electrode, the lack of well-defined experimental workflows, and difficulty interpreting particle behavior within a liquid.

Chemical activation of atom-precise Pd nanoclusters on γ-AlO supports for transfer hydrogenation reactions.

Deposition of atom-precise nanoclusters onto solid supports is a promising route to synthesize model heterogeneous catalysts. However, to enhance nanocluster-support interactions, activation of the nanoclusters by removal of surface ligands is necessary. Thermal treatment to remove surface ligands from supported metal nanoclusters can yield highly active heterogeneous catalysts, however, the high temperatures employed can lead to poor control over the final size and speciation of the nanoclusters.

Impact of palladium/palladium hydride conversion on electrochemical CO reduction via in-situ transmission electron microscopy and diffraction.

Electrochemical conversion of CO offers a sustainable route for producing fuels and chemicals. Pd-based catalysts are effective for converting CO into formate at low overpotentials and CO/H at high overpotentials, while undergoing poorly understood morphology and phase structure transformations under reaction conditions that impact performance. Herein, in-situ liquid-phase transmission electron microscopy and select area diffraction measurements are applied to track the morphology and Pd/PdH phase interconversion under reaction conditions as a function of electrode potential.

Optimized Lithography-Free Fabrication of Sub-100 nm NbO Nanotube Films as Negative Supercapacitor Electrodes: Tuned Oxygen Vacancies and Cationic Intercalation.

The direct growth of sub-100 nm thin-film metal oxides has witnessed a sustained interest as a superlative approach for the fabrication of smart energy storage platforms. Herein, sub-100 nm Zr-doped orthorhombic NbO nanotube films are synthesized directly on the Nb-Zr substrate and tested as negative supercapacitor electrode materials. To boost the pseudocapacitive performance of the fabricated films, supplement Nb active sites (defects) are subtly induced into the metal oxide lattice, resulting in 13% improvement in the diffusion current at 100 m V/s over that of the defect-free counterpart.