Dr Peter R Birkin BSc, PhD
Senior Lecturer in Electrochemistry, Director of UG Programmes
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Dr Peter R Birkin is Senior Lecturer in Electrochemistry within Chemistry at the University of Southampton.
‘My work has centred on the phenomena of cavitation; this is both a fascinating and experimentally challenging arena but ultimately this work has led to a number of exploitable technologies.’
My research group investigate the use of novel electrodes, sensors and electrochemical techniques. These are then used to investigate unusual environments with a particular emphasis on transient events. For example, we have investigated the effects of bubbles on electrochemical processes. In many cases, we either produce these bubbles or excite them using sound. Initially this was centred on the effect of ultrasound on mass transport and surface processes at a variety of different electrodes. However, we have studies acoustically excited tethered bubbles, cavitation in oil, particles in liquids and the group centred and led in chemistry produced a set of new surface cleaning technologies.
Many of the phenomena we investigate are associated with complex dynamic environments. While this is of interest, it is insightful to be able to isolate individual events and probe their behaviour with high accuracy. To investigate these individual events, we have adopted the use of microelectrodes (typically microdisk electrodes with diameters in the range 250 µm – 1 µm) combined with new measurement strategies.
Microelectrodes have many advantages when compared to their larger macroelectrode counterparts and are well suited to the study of cavitation/bubble/particle dynamics at the solid/liquid interface. First, microelectrodes are able to resolve individual cavitation events because of a size exclusion principle. Each bubble that is formed in the solution above the electrode essentially shields the electrode from other cavitation events. In essence, the electrode acts as a target for the imploding bubbles and bubble motion registering the mass transfer effect of each phenomenon as a series of current time transients. The closer to the surface, the more energetic the event and the larger the effect detected at the microelectrode. Second, because of the electrochemical characteristics (a property inversely proportional to the microelectrode's dimensions), the electrode is more suited to the resolution of individual events. This approach was used to follow individual mass transfer events and surface erosion/corrosion events as the result of single cavitation events produced by continuous ultrasound or single bubbles produced by energy discharge into the fluid (for example single cavitation bubbles produced by laser action).
My group has extended our work to investigate a number of sonochemical reactions within simple but well controlled sonochemical reactors. Here, it is vital that a well-controlled acoustic environment is maintained. We have achieved this through modelling of the acoustics within the electrochemical cells that we have employed in our research. These acoustic models can then be verified by comparison with imaging, acoustic emission and electrochemical experiments.
Other projects include the enhancement of electrode plating, the understanding of hydrodynamic voltammetry, novel scanning spectroelectrochemical systems, in situ electrochemical cleaning detection, crystal fragmentation, micropores, nanoelectrodes and nanopores.
We have developed high-speed impedance approaches suitable for the detection and characterisation of bubbles and particles as they move across and interact electrode surfaces. This technique showed for the first time that the growth and collapse of cavitation bubbles occurred prior to the detection of conventional electrochemical signals. We have also developed new methods to detect particle translocation through pores and new strategies for the detection and characterisation of micro and nanobubbles.
Much of the work has been associated with water electrolytes. However, we have also investigated oils and characterised new bubble dynamics in these environments. The work shows promise in food processing situations as the material produced have different characteristics and form faster within the environments we have deployed.