Graphitized Carbon: A Promising Stable Cathode Catalyst Support Material for Long Term PEMFC Applications

Abstract

Stability of cathode catalyst support material is one of the big challenges of polymer electrolyte membrane fuel cells (PEMFC) for long term applications. Traditional carbon black (CB) supports are not stable enough to prevent oxidation to CO2 under fuel cell operating conditions. The feasibility of a graphitized carbon (GC) as a cathode catalyst support for low temperature PEMFC is investigated herein. GC and CB supported Pt electrocatalysts were prepared via an already developed polyol process. The physical characterization of the prepared catalysts was performed using transmission electron microscope (TEM), X-ray Powder Diffraction (XRD) and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis, and their electrochemical characterizations were conducted via cyclic voltammetry(CV), rotating disk electrode (RDE) and potential cycling, and eventually, the catalysts were processed using membrane electrode assemblies (MEA) for single cell performance tests. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SEM) have been used as MEA diagonostic tools. GC showed superior stability over CB in acid electrolyte under potential conditions. Single cell MEA performance of the GC-supported catalyst is comparable with the CB-supported catalyst. A correlation of MEA performance of the supported catalysts of different Brunauer–Emmett–Teller (BET) surface areas with the ionomer content was also established. GC was identified as a promising candidate for catalyst support in terms of both of the stability and the performance of fuel cell.

Impact of Highly Stable Catalyst Support Materials on Polymer Electrolyte Membrane Fuel Cell Performance

“…Both resulting in reduced MEA performances . We already showed the impact of ionomer amount on the CL to the MEA performances in our previous publications . However, in this work, we established a correlation of MEA performance, ionomer amount, and the BET surface areas of the support materials.…”

“…Figure shows the sensitivity of ionomer on MEA performance while using Pt/SC1 as catalyst. At 0.74 ionomer‐to‐carbon ratio ( I / C ), which was found optimum for CB supported catalyst, the worst MEA performance was showed in case of Pt/SC1 catalyst. Probably, a thick layer of ionomer is produced on the CL, resulting in an increase in the mass transport resistance of the reactant.…”

“…For example, it should have high surface area, chemical and thermal stability, mechanical strength, electrical conductivity, effective metal support interactions, and catalyst particles that can uniformly be dispersed on its surface . Highly stable carbon‐based and noncarbon or inorganic cathode catalyst supports for PEMFCs are proposed by different scientists, as shown in previous studies. Graphitized carbons are found to be promising catalyst support materials in terms of both stabilities and activities as compared to nongraphitized carbon supports .…”

Electrocatalysts for PEM Fuel Cells

“…To develop catalyst support materials that are stable at high potentials, considerable work has been done on carbon‐based materials with increased graphitic properties and non‐carbon electro‐conductive support materials including carbides, nitrides, doped diamonds, and oxides . Especially, conducting metal oxides of titanium and tin are promising materials because they are assumed to be chemically inert and stable even under harsh cathodic conditions such as a hot water/humidified air‐filled acidic environment, and several papers on tin and titanium oxides have been published .…”

Impact of Membrane Types and Catalyst Layers Composition on Performance of Polymer Electrolyte Membrane Fuel Cells

“…Thus, optimization of the ionomer film in each CL is needed to achieve maximum MEA performance. The optimum ionomer content is depending on the Brunauer, Emmett, and Teller (BET) surface areas of the support materials . Unfortunately, there are no experimental techniques available, except the performance characterization of MEA in a full cell to determine the optimum amount of ionomer needed for each CL.…”