A novel device enabling high-resolution observation of liquid phase dynamic processes at nanoscale

In situ observation and recording of key liquid-phase electrochemical reactions in energy devices is of great importance for the progress of energy science.

A research team led by academics from the City University of Hong Kong (CityU) recently developed a novel, tiny device for holding liquid specimens. transmission electron microscopy (TEM) observation has opened the door for direct visualization and recording of complex electrochemical reactions at the nanoscale in real-time and at high resolution.

The research team believes this innovative method will shed light on strategies for manufacturing powerful research tools for unraveling the mysteries of future electrochemical processes.

The use of a conventional TEM requires a thin, stable solid body due to the vacuum environment within the chamber that holds the specimen (the vacuum environment prevents electrons from being absorbed or deflected along their path and affecting the observation). Limited to samples. Liquid samples are not vacuum compatible and cannot be probed directly with a conventional TEM.

Fortunately, the advent of more advanced in-situ ‘liquid cell TEM’ has made research possible. liquid phase In situ dynamic processes such as crystal nucleation and growth in solution, electrochemical reactions in energy devices, and observation of vital activity in living cells.

The “liquid cell” is the core component of the TEM for holding the sample. electron beam Since it passes through, it is possible to observe on the spot. However, it is difficult to manufacture high quality liquid cells for TEM. This is because the electrodes must be built into a small ‘closed’ liquid cell, encapsulating the electrolyte to prevent leakage, and at the same time being connected to an external power source.

A research team, jointly led by Dr. Zeng Zhiyuan, assistant professor in the Department of Materials Science and Engineering at CityU, and Professor Li Ju from the Massachusetts Institute of Technology (MIT), has successfully developed an efficient and novel method for manufacturing “closed molds.” An electrochemical liquid cell that can greatly improve the resolution of his TEM with liquid samples.

“The newly developed closed liquid cell serves two main tasks: (1) encloses the liquid sample in a closed container and isolates it from the vacuum environment of the microscope; and (2) uses two electrons to , confines the liquid sample in a sufficiently thin liquid layer.Transparent silicon nitride (SiN_X) window, allowing electrons to travel through the liquid layer and image the reaction,” Zeng explained.

In order to fabricate a high-performance ‘closed’ electrochemical liquid cell in this protocol, the research team used advanced nanofabrication techniques, including photolithography, to construct the core component of in situ liquid TEM, the liquid cell. was manufactured. Photolithography is ultraviolet rays A geometric design is transferred from an optical mask to a photosensitive chemical (photoresist) coated on the substrate.

The team manufactured the lower and upper chips separately and assembled them. A gold or titanium electrode was deposited on the bottom tip during the metal deposition process. The electrolyte was then loaded into the liquid cell and sealed.

Using this innovative liquid cell and transmission electron microscope, the dynamic electrochemical reactions of liquid samples on electrode surfaces can be observed in real time at high resolution via a TEM operating system embedded in a high spatiotemporal resolution camera. You can record.

“Electrochemical liquid cells designed by our customized nanofabrication method have thinner SiN._X Better imaging window (35nm) than commercial one (50nm). It also has a thinner liquid layer (150 nm) than the commercially available one (1,000 nm). Thin SiN_X Due to the imaging window and thin liquid layer, the fabricated liquid cell can capture electrochemical reactions with better TEM spatial resolution than commercial cells. ”

The team believes that many opportunities and applications for in situ TEM observation of electrochemical reactions will emerge shortly after the development of electrochemical liquid cells through the selection of patterned metal electrodes and encapsulated liquid electrolytes within the liquid cell. thinking about.

This newly proposed fabrication protocol can also be used in other field techniques beyond TEM. For example, appropriate adjustments to this protocol are suitable for fabrication of electrochemical liquid cells for in-situ X-ray characterization of electrochemical reactions (X-ray absorption spectroscopy, X-ray diffraction, etc.).

The survey results are nature protocol.