PGM-free catalysts

The growth of the market for devices (mainly fuel cells and metal-air batteries) using platinum-based catalysts is limited by cost and availability of Pt itself, which makes finding alternatives an extremely important research topic. Our group focuses on two main strategies, the use of Pt in alloys or in combination with metal oxides (vide supra) and the use of non-precious metals in the so-called non-precious group metal catalysts.

Metal-, nitrogen- and carbon-based catalysts are the most studied class of materials due to the good response toward the catalysis of oxygen reduction reaction (ORR). Nitrogen- and iron-doped carbon material (Fe-N-C) has been intensely studied due to their high catalytic activity, and intensive research is ongoing to understand the nature of the active sites, their stability, and the mechanisms of their formation and reaction during ORR.

Here we have deeply studied several aspects of material fabrication, which can influence formation of the active sites and their activity, such as morphology of the carbon support, iron-nitrogen precursor ligand structure and effect of co-doping with sulphur, just to give some examples. All these studies are needed due to the complexity of the system (see figure on the left) in order to understand how the desired site (FeN4) are preferentially formed.

Recently we have moved to the study of bimetallic systems based on Fe-N-C by introducing Sn and Sb, which have been less studied. In general, a bimetallic system can show both better performance due to possible synergy of two metals or worst activity due to site formation inhibition.