Probing electrochemical surface/interfacial reactions with liquid cell transmission electron microscopy: a challenge or an opportunity?

Understanding electrochemical reactions at material surfaces and interfaces is crucial for the development of next-generation battery electrodes and electrocatalysts - two key areas in global CO2 mitigation strategies. By allowing these dynamic reactions to be captured on an atomic level and in real-time, the liquid cell transmission electron microscopy (LC-TEM) technique has carved itself a niche in energy materials research. Several key problems are being investigated, ranging from addressing dendrite growth in lithium-ion batteries that cause a thermal runaway, to understanding mass loss of expensive platinum catalysts in native hydrogen fuel-cell environments. Unfortunately, as with any emerging technology, LC-TEM is not without its share of problems. Undesired electron beam interactions with the liquid, low containable liquid volumes, and poor spatial resolution due to plural scattering are only some of the many problems which must still be fully resolved. This short review highlights the strengths and weaknesses behind LC-TEM while providing updates on the latest applications and technical advances in the areas of dose-minimization strategies, improvements in analytical abilities, and novel closed-cell design. Notable future opportunities include off-axis holography, diffraction tomography, and pump-probe laser excitations - all carried out in liquids.