Researchers at Lawrence Berkeley National Laboratory (Berkeley Lab) developed a way to study electrochemical processes at the atomic level with unprecedented resolution, resulting in new insights into a popular catalyst material. They published their findings in Nature.
Scientists have developed a cell that holds all the components of an electrochemical reaction. They paired this with transmission electron microscopy (TEM) to view the reactions at an atomic scale.
Their device, dubbed a polymer liquid cell (PLC), can be frozen to stop the reaction at specific time points, allowing them to view the composition changes at each stage with other characterization tools. The team is using their cell to study a copper catalyst that reduces carbon dioxide to generate fuels.
According to Haimei Zheng, lead author and senior scientist in Berkeley Lab’s Materials Science Division, her team is excited to use the PLC on various other electrocatalytic materials, including lithium and zinc batteries.
The researchers tested their approach on a copper catalyst system, using powerful microscopes at the National Center for Electron Microscopy, part of Berkeley Lab’s Molecular Foundry, to study the reaction where the solid catalyst with an electrical current through it meets the liquid electrolyte. The catalyst system they used was solid copper with an electrolyte of potassium bicarbonate (KHCO3) in water. The cell is composed of platinum, aluminum oxide, and a super thin, 10 nanometer polymer film. They captured unprecedented images and data showing unexpected transformations at the solid-liquid interface during the reaction.
Copper atoms left the solid, crystalline metal phase and mingled with carbon, hydrogen, and oxygen atoms from the electrolyte and CO2 to form a fluctuating, amorphous state between the surface and the electrolyte. They named it the “amorphous interphase” as it is neither solid nor liquid. It disappears when the current stops flowing, and most of the copper atoms return to the solid lattice.
“… The discovery of the amorphous interphase challenges our previous understanding of solid-liquid interfaces, prompting a need to consider its effects when devising strategies,” said Zhang.
