Adriaan Jeremiasse, Matija Lovrak, Nitin Prasad, Jan Vos, Magneto special anodes (Xylem), Schiedam, The Netherlands
Clean energy technologies, such as windmills, battery electric vehicles and green hydrogen production require directly or indirectly, titanium-based electrodes that consist of critical raw materials (CRMs). Hence, there is an increasing demand for these CRMs to enable the energy transition. Titanium based electrodes consist of a titanium substrate, coated with a platinum group metal (PGM) coating, e.g. Platinum or Iridium Mixed Metal Oxides (MMO). These coatings are still mostly applied using the original process described by Henri Beer in 1965: a wet-chemical route, followed by a thermal decomposition step. Ideally, the PGMs are fully substituted by non-PGMs, however, the electrodes are used under strongly acidic and anodic conditions, in which non-PGM catalysts do not survive sufficiently long. Hence, strategies aim at partially substituting these PGMs, while retaining functionality and durability (service life). These strategies rely on a thorough understanding of the electrode failure mechanism in the electrochemical application. Electrode failure may be caused e.g. by depletion of the active catalyst through dissolution, or by passivation or corrosion of the titanium substrate. In this presentation, we will give an overview of performance criteria and typical failure mechanisms of electrode coatings in various applications. We will present different approaches in coating design to decrease the PGM loading, while improving electrode performance and durability. These new approaches make use of wet chemistry as well alternative deposition techniques, such as physical vapor deposition.