Adina Morozan

Low-platinum and platinum-free catalysts for the oxygen reduction reaction at fuel cell cathodes

Fuel cell reactions invariably involve an oxygen reduction reaction (ORR) at the cathode, which is one of the main rate-decreasing steps on platinum (Pt)-catalysts in the water formation reaction and energy conversion efficiency in polymer electrolyte membrane fuel cells (PEMFCs). The Pt scarcity and cost have led to the development of alternative catalyst materials for fuel cell applications. This paper reviews ORR catalysts with regard to their classification, mechanism, activity and performances. From conventional Pt-based catalysts to non-noble metal or bio-inspired catalysts, we show how significant progresses were made in ORR catalysis.

Metal organic frameworks for electrochemical applications

Metal–organic frameworks (MOFs) have received huge attention in the last years as promising porous materials with unrivalled degree of tunability for a wide range of applications including gas storage or separation, catalysis, drug delivery and imaging. The present review appraises the application of MOFs in the field of electrochemistry. From materials for rechargeable batteries, supercapacitors and fuel cells to electrocatalysis or corrosion inhibition, MOFs or MOF-derived materials are gaining momentum in this field. For real breakthroughs, combining their electrochemical properties with appropriate electronic and ionic conductivity will be required.

Carbon Nanotube-Templated Synthesis of Covalent Porphyrin Network for Oxygen Reduction Reaction

The development of innovative techniques for the functionalization of carbon nanotubes that preserve their exceptional quality, while robustly enriching their properties, is a central issue for their integration in applications. In this work, we describe the formation of a covalent network of porphyrins around MWNT surfaces. The approach is based on the adsorption of cobalt(II) meso-tetraethynylporphyrins on the nanotube sidewalls followed by the dimerization of the triple bonds via Hay-coupling; during the reaction, the nanotube acts as a template for the formation of the polymeric layer. The material shows an increased stability resulting from the cooperative effect of the multiple π-stacking interactions between the porphyrins and the nanotube and by the covalent links between the porphyrins. The nanotube hybrids were fully characterized and tested as the supported catalyst for the oxygen reduction reaction (ORR) in a series of electrochemical measurements under acidic conditions. Compared to similar systems in which monomeric porphyrins are simply physisorbed, MWNT-CoP hybrids showed a higher ORR activity associated with a number of exchanged electrons close to four, corresponding to the complete reduction of oxygen into water.

Metal-free nitrogen-containing carbon nanotubes prepared from triazole and tetrazole derivatives show high electrocatalytic activity towards the oxygen reduction reaction in alkaline media.

High-performance oxygen reduction reaction (ORR) catalysts based on metal-free nitrogen-containing precursors and carbon nanotubes are reported. The investigated systems allow the evaluation of the effect of nitrogen-containing groups towards ORR and the results show that the catalysts are compatible with the conditions encountered in alkaline fuel cells, exhibiting good catalytic activity and stability compared with conventional Pt/C electrocatalyst.