Visualising electrochemistry using Magnetic Resonance Imaging

The design and development of improved electrochemical technologies, such as corrosion prevention or energy storage, requires understanding of the transport and concentration gradients of electroactive species within these devices during operation. However, there are few methods that are able to visualise and quantify these spatially, in situ and in real time. Magnetic resonance imaging (MRI) has proven to be an excellent tool for non-invasively studying complex, spatially heterogeneous chemical systems in materials, engineering and chemical research [1] . While MRI has enormous potential for in situ investigation of the spatial distribution, speciation, and mobility of molecules and ions in electrochemical devices, there are currently very few examples of MRI being used to probe such systems. This is largely due to the experimental challenges associated with setting up an electrochemical cell inside a strong magnetic field and the imaging artefacts caused by the presence of metals that lead to undesirable variations in the radiofrequency (RF) and magnetic fields across the sample [2] . However, recent papers [3] have shown that such issues can be overcome and that it is possible to collect viable, quantitative, in situ data.

This paper will review the challenges associated with imaging electrochemical cells which contain bulk metals and the latest advances we have made in overcoming these challenges. MRI data will be presented for mapping electrochemistry during the corrosion of copper (figure 1) and a model battery.

Figure 1 A time series of T1 relaxation time maps during the corrosion of copper in a 1 M NaCl electrolyte.