New method to optically monitor electrochemical reactions at nanoscale

Many technological applications, such as sensors and batteries, greatly rely on electrochemical reactions. Improving these technologies depends on understanding how electrochemical reactions work. However, most current methods cannot look at electrochemical reactions in detail. Scientists at Utrecht University have now developed a new method that overcomes this limitation. This provides a powerful new way to study and improve electrochemical processes. The study was recently published in PNAS.

Hydrogen production by water electrolysis is one example where electrochemical reactions at electrodes matter for sustainable technology. But the decisive steps happen within just a few nanometers of the electrode surface, which is too small for most conventional methods to resolve.  

Nanoholes

Researchers at Utrecht University, together with colleagues at East China University of Science and Technology, have now developed a new technique that can monitor electrochemical reactions on the nanoscale. The technique is called Opto-Iontronic Microscopy and involves an optical microscope. The electrochemical reactions occur in a single tiny hole, or nanohole. By shining light on the nanohole and measuring how the scattered light changes, the technique provides a local readout of electrochemical activity inside this nanometer-sized region.

It opens up new opportunities for analysis of electrochemical reactions in tiny environments

Powerful new technique

It is a powerful, new technique to monitor electrochemical reactions on the nanoscale, according to physicist Zhu Zhang, who is first author of the study. “It opens up new opportunities for analysis of electrochemical reactions in tiny environments”, he says. The new method was tested with a model electrochemical reaction called ferrocenedimethanol redox reaction. Also, the measurements were compared to the outcomes of a theoretical model for electrochemical processes.

Opto-Iontronic Microscopy has an important advantage over other techniques to study reactions at such small scale. An electron microscope, for example, operates in high vaccuum, which requires sample preparation. Opto-Iontronic Microscopy allows to study reactions under real working conditions. Samples need no preparation and the conditions reflect the real world. These advantages make the technique relatively cheap. Although its resolution is currently lower than in electron microscopy, it is still high, measuring every millisecond.

The method is relevant for many fields of research that involve the study of electrochemical reactions. Hydrogen and fuel technologies, such as water electrolysis, are just one example. Other potential areas are materials and interface research, such as catalyst design, and analytical/environmental electrochemistry, including electrochemical sensing and environmentally relevant electrochemical processes.

Ready for use

The technique is ready for use, and Zhang has been in contact with people from various research fields to collaborate within areas such as hydrogen evolution and circular batteries. In one of the projects, Zhang and his team aim to develop a prototype for the safe and scalable storage of hydrogen. Current storage methods are relatively unsafe and demand much energy.

Opto-Iontronic Microscopy helps this project by directly visualizing ion and hydrogen transport inside storage materials at the nanoscale in real time, revealing where energy losses and safety risks arise and guiding the design of safer, more efficient hydrogen storage materials. The project recently received funding from a scientific community at Utrecht University, called Pathways to Sustainability.