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Nanoscale Electrochemistry on Light Metallic Alloys

Periodic Reporting for period 1 - NELMA (Nanoscale Electrochemistry on Light Metallic Alloys)

Reporting period: 2018-06-01 to 2020-05-31

In the last decades, light metal alloys have received considerable attention due to their high specific strength, light density, recyclability, biodegradability and high theoretical density storage. Due to the combination of these unique properties, light metal alloys are in high demand for diverse practical applications: in space, automobile etc. industries as the structural material; in the energy sector for the replacement of Li-based batteries; and in biomedical applications as biodegradable bio-implants. All of these areas are of huge importance for the economy, quality of life and future technological developments in Europe.

The main limitation for the widespread use of these materials remains the unknown mechanisms of their degradation and, as a result, absence of effective strategies of corrosion protection. It is known that light metal alloys are nanostructured to expose particular surface sites, but probing the intrinsic activity of these sites is usually beyond current experimental capability. In this project, we present a new tool that makes use of a special probe (known as “scanning probe”) to measure the functional properties of light metal alloys in minute detail in order to guide the development of more durable materials.

In essence, we developed and implemented a range of “scanning probe” techniques to measure functional (electrochemical) information during metal dissolution with unprecedented spatial resolution, which is broadly relevant for corrosion applications. We effectively showed that this novel approach is generally applicable to the degradation of polycrystalline metals by applying it to study the corrosion of zinc and iron. In addition, we adapted the “scanning probe” technology to explore local properties of the double layer on metal interfaces, thereby complementing the toolbox of local electrochemical methods for materials characterization.
The first body of the work in this project was dedicated to the optimization of experimental conditions in “scanning probe” technique for the investigation of local activities of corroding interfaces. Active metal dissolution during electrochemical probing compromised the reproducibility of the “scanning probe” technique. We discovered that the environment plays a crucial role in the stability of the measurement. In particular, application of a hydrophobic oil on metal interface or oxygen removal can significantly improve the experimental conditions. These allowed the use of “scanning probe” techniques to reveal activities of single grains on polycrystalline iron and zinc. All measurements were complemented with computational quantum mechanical modelling and successfully rationalized using computed free adsorption and dissolution energies. These works were disseminated via publication:

L. C. Yule et al., “Nanoscale Active Sites for the Hydrogen Evolution Reaction on Low Carbon Steel”, The Journal of Physical Chemistry C, 2019, 123 (39), 24146-24155.

L. C. Yule et al., “Nanoscale electrochemical visualization of grain-dependent anodic iron dissolution from low carbon steel”, Electrochimica Acta, 2020, 332, 135267.

V. Shkirskiy et al., “Scanning Electrochemical Cell Microscopy and Correlative Surface Structural Analysis to Map Anodic and Cathodic Reactions on Polycrystalline Zn in Acid Media”, Journal of The Electrochemical Society, 2020, 167 (4), 041507

The latter study produced a lot of interest, with presentation given on international conference dedicated to corrosion “Eurocorr2019” (Seville, Spain).

After completing these works, significant focus was given to further development of “scanning probe” techniques, specifically to the investigation of properties of double layer on metal interfaces. This allowed us to interrogate minute structural features of double layer of gold nanoparticles. This work was disseminated via publication:

V. Shkirskiy et al., “Nanoscale Electrochemical Impedance Measurements in Scanning Ion Conductance Microscopy”, submitted to ACS Analytical Chemistry.

Over the project period, one review article was published addressing various aspects of the use of the “scanning probe”:

C. L. Bentley et al., “Nanoscale electrochemical mapping”, ACS Analytical Chemistry, 2018, 91 (1), 84-108.

In summary, this project led to the development of novel methodologies for probing metal interfaces. The “scanning probe” techniques have been used to investigate a range of phenomena in corrosion complemented with quantum mechanical modeling.
The work performed during this project was entirely original and innovative, pushing the state-of-the-art in terms of “scanning probe” application to actively corroding metal interfaces, meaning these techniques can now be used to investigate new class of materials with minute detail. We predominantly used these techniques to investigate metal dissolution and hydrogen evolution reactions, a critically important processes in corrosion and energy sector for the so-called “hydrogen economy”. The developed “scanning probe” techniques have shown to be powerful to reveal dynamics of metal interfaces and have the potential for developing considerable new knowledge for a rational design of durable metal materials. Overall, there is no doubt that this project was highly successful leading to the publications of high impact articles as well as to the establishment of multiple collaborations.
Identification of local corrosion sites on metals drives the design of more durable materials