researchers at the pacific northwest national laboratory (pnnl) have designed a new device to add designer molecules to an electrochemical cell and characterize the electrode-electrolyte interface while the cell is being charged and discharged to better understand the reactions taking place inside energy storage devices.

designed at pacific northwest national laboratory, the device lets scientists add designer
molecules to an extremely well-defined electrochemical cell. (mike perkins/pnnl)

according to a report on the pnnl website, this study of reactions in real-time in controlled gaseous environments can be used to build better batteries, fuel cells, and energy storage devices.

the article noted, “determining what happens at the meeting point has been difficult because in addition to active molecules, interfaces often contain numerous inactive components… the device provides a way to understand the basic breakdown reactions, material build-up, and other processes at the electrode surface during operation.”

the device incorporates a solid ionic-liquid membrane that has transport properties similar to a liquid electrolyte (in vacuum or well-controlled environments). the scientists place active molecules, such as catalytic metal clusters, on the membrane (in a process called soft-landing) to study the interaction.

“in an exciting new twist, scientists can also add molecular fragments to the cell,” the article added. “they create the fragment ions by ‘smashing’ precursor molecules in the gas phase. these gas-phase fragments may then be selected and added to the membrane. the result is a well-defined film that you can't typically make in solution.”

when the soft-landed clusters diffuse through the membrane to reach the electrode of the device, the researchers can study the precise reaction through electrochemical and spectroscopic techniques.

the study was recently published in proceedings of the national academy of sciences. the abstract stated:

“molecular-level understanding of electrochemical processes occurring at electrode–electrolyte interfaces (eeis) is key to the rational development of high-performance and sustainable electrochemical technologies. this article reports the development and application of solid-state in situ thin-film electrochemical cells to explore redox and catalytic processes occurring at well-defined eeis generated using soft-landing (sl) of mass- and charge-selected cluster ions.

“in situ cells with excellent mass-transfer properties are fabricated using carefully designed nanoporous ionic liquid membranes. sl enables deposition of pure active species that are not obtainable with other techniques onto electrode surfaces with precise control over charge state, composition, and kinetic energy. sl is, therefore, demonstrated to be a unique tool for studying fundamental processes occurring at eeis.

“using an aprotic cell, the effect of charge state (pmo12o3−/2−40pmo12o403-/2-) and the contribution of building blocks of keggin polyoxometalate (pom) clusters to redox processes are characterized by populating eeis with pom anions generated by electrospray ionization and gas-phase dissociation. additionally, a proton-conducting cell has been developed to characterize the oxygen reduction activity of bare pt clusters (pt₃₀ ∼1 nm diameter), thus demonstrating the capability of the cell for probing catalytic reactions in controlled gaseous environments.

“by combining the developed in situ electrochemical cell with ion sl we established a versatile method to characterize the eei in solid-state redox systems and reactive electrochemistry at precisely defined conditions. this capability will advance the molecular-level understanding of processes occurring at eeis that are critical to many energy-related technologies.”