New technology provides electrifying insights into how catalysts work at the atomic level

A team led by Lawrence Berkeley National Laboratory (Berkeley Lab) has invented a technique to study electrochemical processes at the atomic level with unprecedented resolution and used it to gain new insights into a popular catalyst material.

Electrochemical reactions—chemical transformations that are caused by or accompanied by the flow of electric currents—are the basis of batteries, fuel cells, electrolysis, and solar-powered fuel generation, among other technologies. They also drive biological processes such as photosynthesis and occur under the Earth's surface in the formation and breakdown of metal ores.

The scientists have developed a cell—a small enclosed chamber that can hold all the components of an electrochemical reaction—that can be paired with transmission electron microscopy (TEM) to generate precise views of a reaction at an atomic scale. Better yet, their device, which they call a polymer liquid cell (PLC), can be frozen to stop the reaction at specific timepoints, so scientists can observe composition changes at each stage of a reaction with other characterization tools.

In a paper appearing in Nature, the team describes their cell and a proof of principle investigation using it to study a copper catalyst that reduces carbon dioxide to generate fuels.

"This is a very exciting technical breakthrough that shows something we could not do before is now possible. The liquid cell allows us to see what's going on at the solid-liquid interface during reactions in real time, which are very complex phenomena. We can see how the catalyst surface atoms move and transform into different transient structures when interacting with the liquid electrolyte during electrocatalytic reactions," said Haimei Zheng, lead author and senior scientist in Berkeley Lab's Materials Science Division.

"It's very important for catalyst design to see how a catalyst works and also how it degrades. If we don't know how it fails, we won't be able to improve the design. And we're very confident we're going to see that happen with this technology," said co-first author Qiubo Zhang, a postdoctoral research fellow in Zheng's lab.

Zheng and her colleagues are excited to use the PLC on a variety of other electrocatalytic materials, and have already begun investigations into problems in lithium and zinc batteries. The team is optimistic that details revealed by the PLC-enabled TEM could lead to improvements in all electrochemical-driven technologies.

New insights into a popular catalyst

The scientists tested the PLC approach on a copper catalyst system that is a hot subject of research and development because it can transform atmospheric carbon dioxide molecules into valuable carbon-based chemicals such as methanol, ethanol, and acetone. However, a deeper understanding of copper-based CO₂ reducing catalysts is needed to engineer systems that are durable and efficiently produce a desired carbon product rather than off-target products.

Zheng's team used the powerful microscopes at the National Center for Electron Microscopy, part of Berkeley Lab's Molecular Foundry, to study the area within the reaction called the solid-liquid interface, where the solid catalyst that has electrical current through it meets the liquid electrolyte. The catalyst system they put inside the cell consists of 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.