Playing with the catalyst architecture to compensate for platinum-group metals removal
Platinum is the rock star as a water reduction electrocatalyst, particularly in acidic media. However, its low abundance and high price makes it necessary to envision new platinum-free electrocatalysts. The same holds when we look at the oxygen reduction reaction side in a proton exchange membrane fuel cell. Options are not so obvious when it comes to transition metals and full replacement of platinum is often accompanied by a decrease of the catalytic activity. While some alternatives in the form of alloys or composites show promising results, their long-term durability is often compromised. Corrosion-related issues appear and profound leaching of the material catalyst is unavoidable.
Playing with the catalyst architecture while keeping its composition free from platinum is a convenient strategy to couple high electrocatalytic performance and good durability in acidic media. The introduction of porosity in the catalyst material has been the focus of intense research in the last years. Electrodeposition emerges as an ideal technique for this purpose. Thus, metals and alloys with controlled porosity can be produced by electrodeposition using various strategies, giving rise to nano-architectured electrocatalysts with a very large surface-to-volume ratio. An important aspect to consider is that most catalysts in powder form require a binder to anchor them on a conductive substrate. On the contrary, since the catalyst is deposited directly on the substrate by electrodeposition, the use of binders is avoided. Indeed, binder-free electrocatalysts have become increasingly popular, owing to their enhanced electron transfer and improved mass diffusion.
In NICKEFFECT, we opt for electrochemical approaches (electrodeposition and electroless deposition) to produce porous, platinum-free electrocatalysts featuring a large surface-to-volume ratio and we strive to increase its life-time in moderately aggressive media. Even if the standards of platinum are not met, the immense reduction of costs underpins the significance of the research. We are facing an energy transition towards a model based on savings, efficiency and sustainability and its impact on the global economy is already there.