Non-noble metal (NNM) catalysts for Fuel Cells: tuning the activity by a rational step by step single variable evolution

Low temperature fuel cells (LTFCs) based on polymer electrolyte membranes (PEMs) fed with hydrogen are being recognized to be among the best candidates as pollution-free and energy-saving power sources for electric or hybrid vehicles or portable apparatuses because of their high energy conversion efficiency (~58%) and zero or nearly zero emissions. Currently, cost and durability are the main limitations of FC technology to be commercialized. A significant percentage of the cost of PEMFCs comes from precious group metal (PGM) based catalysts that are used mainly for the oxygen reduction reaction (ORR). Therefore, a breakthrough in the development of cost effective, highly performing and durable catalysts has been identified as the determining factor for success toward PEMFC commercialization. In particular, non-noble metal (NNM) cathodic electrocatalyst gained lots of attention in recent years to replace PGM-based catalysts for the ORR. Within various NNM electrocatalysts, the most promising ones seem to be heat-treated Fe(II) and/or Co(II) chelates and macrocycles supported on carbon particles. The formation of metal-nitrogen (M-NX/C) and metal-carbon (M/C) active ensembles after the heat-treatment is necessary for ORR. In this chapter we will describe an enhancement of the electrochemical activity toward ORR through a step-by-step understanding of the variables involved during the formation of active Fe-NX NNM catalysts. We adopted different approaches in order to understand the formation of active ensembles and to increase the activity by a rational step-by-step progression

Optimization of a Fe-N-C electrocatalyst supported on ordered mesoporous carbon functionalized with polypyrrole for oxygen reduction reaction

In this work a Fe-N-C non-noble metal electrocatalyst for oxygen reduction reaction (ORR) is optimized. The catalyst is synthesized using mesoporous carbon (MPC) as C source, polypyrrole (PPY) as N source and Fe(II) acetate. In the first part, the influence of the addition of a surfactant, and of a heat treatment of the MPC-PPY support before the impregnation with Fe(II) ions is investigated. In the second part, the best catalyst obtained in the first part is used as support, and the influence of a second pyrolysis treatment performed with or without further impregnation with Fe(II) is investigated. Materials are characterized by SEM-EDX, BET-porosimetry, XPS and TEM analyses. The electroactivity towards ORR was tested with a rotating disk electrode in acidic and alkaline conditions. An evident increase of electroactivity after the second heat treatment is found, as well as a concomitant increase of surface area and micropore content

3D multi-physic modeling and validation of a gas diffusion electrode for analyzing transport and kinetic phenomena of noble and non-noble based catalysts for PEMFC

A 3D multi-physics, multi-phase, multi-component and non iso-thermal model is developed to analyze the effects of catalyst structures on the performance of a gas diffusion electrode (GDE). The model includes Stokes-Brinckman, Maxwell-Stefan, Flory-Huggins and modified Butler-Volmer equations for simulating the performance of a GDE, solved by Comsol® Multiphysics v4.4 platform. The model was validated against experimental data, showing congruent and convergent response for different catalytic layers, confirming the accuracy of the model and the equations applied. The use of a 3D model considering porous materials can be used for evaluating intrinsic parameters of new novel electrocatalysts