Electron Beam Transparent Boron Doped Diamond Electrodes for Combined Electrochemistry─Transmission Electron Microscopy

Abstract

The majority of carbon based transmission electron microscopy (TEM) platforms (grids) have a significant sp2 carbon component. Here, we report a top down fabrication technique for producing freestanding, robust, electron beam transparent and conductive sp3 carbon substrates from boron doped diamond (BDD) using an ion milling/polishing process. X-ray photoelectron spectroscopy and electrochemical measurements reveal the sp3 carbon character and advantageous electrochemical properties of a BDD electrode are retained during the milling process. TEM diffraction studies show a dominant (110) crystallographic orientation. Compared with conventional carbon TEM films on metal supports, the BDD-TEM electrodes offer superior thermal, mechanical and electrochemical stability properties. For the latter, no carbon loss is observed over a wide electrochemical potential range (up to 1.80 V vs RHE) under prolonged testing times (5 h) in acid (comparable with accelerated stress testing protocols). This result also highlights the use of BDD as a corrosion free electrocatalyst TEM support for fundamental studies, and in practical energy conversion applications. High magnification TEM imaging demonstrates resolution of isolated, single atoms on the BDD-TEM electrode during electrodeposition, due to the low background electron scattering of the BDD surface. Given the high thermal conductivity and stability of the BDD-TEM electrodes, in situ monitoring of thermally induced morphological changes is also possible, shown here for the thermally induced crystallization of amorphous electrodeposited manganese oxide to the electrochemically active γ-phase.

Impedimetric Measurement of Exchange Currents and Ionic Diffusion Coefficients in Individual Pseudocapacitive Nanoparticles

“…When the droplet contains an electroactive nanoparticle, the thermodynamic and kinetic properties of the reaction occurring at that particle can be measured. Because of this simple and elegant mode of operation, SECCM has been applied to study a wide range of electroactive materials, including the activity of various electrocatalysts, ,− charge storage in individual pseudocapacitors, , and the intercalation of ions in battery active materials. − Its powerful compatibility with complementary microstructure imaging and characterization techniques, which measure topography, morphology, or composition, can offer unprecedented insight into structure–property relationships at the nanoscale. ,− …”

Polycrystalline Diamond Micro‐Hotplates

“…Despite being optically opaque, the electron transparency of <100 nm thick boron-doped diamond tied with its chemical inertness also makes the material suitable for the fabrication of single material heater stages for use within ultra-high-resolution imaging, with the sample under investigation able to be placed directly in contact with the heating element to avoid any discrepancies in temperature. [10,27] To date however, the extent of diamonds use within such devices has been as a heat-spreading layer to ensure uniform thermalization, or as a resistant capping layer for use in harsh environments. [28,29] The aim of this work is therefore to investigate the utilization of scalable, thin-film polycrystalline diamond (PCD) within single layer micro-hotplates.…”