Electrochemistry: Oxigen Reduction Reaction Electrocatalyst

Electrodeposition of manganese/polypyrrole (Mn/PPy) nanocomposites has been recently shown to be a technologically relevant synthesis method for the fabrication of Oxygen Reduction Reaction (ORR) electrocatalysts.

Bozzini et al., J. Mater. Chem. A (2015).

Novel non-noble metal/polypyrole composites have properties promising to be considered as substitutes of expensive platinum catalysts for the Oxygen Reduction Reaction (ORR) in energy devices, in particular in alkaline fuel cells. Following revelation the catalytic activity of cobalt phthalocyanine and the beneficial effect of pyrolysis at 400–800 °C on its stability and catalytic properties, considerable efforts have been made to explore the chemo-morphological transformations of non-precious metal-nitrogen–carbon composites (M/N/C, M¼Co, Fe, Mn, etc.) during pyrolysis in order to shed light on the modifications leading to the increased electrocatalytic activity. Up to date the majority of the results indicate the formation of MeNx-type moieties as active catalytic sites. Among the different strategies to include nitrogen in the catalyst, electrochemistry offers the possibility of using polypyrrole (PPy) with its dual function as a N-source and an electronically conducting catalyst support for the electrodeposition of metal-containing composite materials.
We used a new approach for the fabrication of MnO2/carbon and metal/PPy electrocatalysts that has allowed creation of more Mn/N/C catalytic active sites during the electrodeposition process. The work, coordinated by Prof. Benedetto Bozzini, is collaboration between the Department of Engineering and Innovation of Salento University, The Institute for Microelectronics and Microsystems, IMM-CNR and Elettra Iaboratory. The investigation combined material fabrication and characterization using clasical electrochemistry methods complemented with imaging and microspectroscopy methods available at the scanning microscopes operated at the TwinMic and ESCAMicroscopy beamlines at Elettra laboratory. In particular, at Elettra by using chemical mapping and X-ray absorption (XAS), fluorescence (XRF) and photoelectron XPS) microspectroscopy we were able to shed light on the evolution of both morphology and chemical composition of synthesized materials following in-situ their evolution under different fabrication conditions.
The representative calibrated Mn XRF images in Fig.1 clearly show the laterally inhomogeneous distribution at mesoscopic and submicrometric scales, achieved under low current densities, while the rationed Mn/O pinpoints the variations in the Mn oxidation state. Comparing the contrast levels of the two maps it is clear that the local concentration and chemical state of Mn are not fully correlated.
Last Updated on Tuesday, 22 December 2015 15:50