John W. Van Zee

Aniline as a Cationic and Aromatic Contaminant in PEMFCs

Aniline as a possible contaminant in polymer electrolyte membrane fuel cells (PEMFCs) has been studied by several ex-situ techniques. The aniline isotherm for MEA shows more affinity to ion-exchange with the PEM than other monovalent such as sodium and ammonium ions, thus indicating stronger performance loss at the same concentration. The results of cyclic voltammetry (CV) of Pt/C show the loss of electrochemical surface area (ECSA) by with the addition of aniline in the electrolyte. The appearance of unknown peaks in CV may indicate the production of polyaniline (PANI) film which appears to grow with the number of CV tests. These studies indicate that the use of balance of plant components that leach aniline should be avoided since its presence appears to decrease the electrochemical activity of the electrode for the oxygen reduction reaction. Further studies on aniline with in-situ experiment may not be warranted.

Understanding Differences in the Performance of Laboratory Scale PEMFCs: I. The Effect of Active-Area

The ability to compare, analyze, and interpret laboratory-scale experimental data for polymer electrolyte membrane fuel cells (PEMFCs) is often limited by differences in the performance between 25 cm2 and 50 cm2 active area cells. The present study includes the material of gas diffusion layers (GDL), their compression pressure, and the operating conditions to quantify and understand the effect of these factors on the performance of PEMFCs with different active area of electrodes. The experimental data show that under the same compression the internal compression pressure is higher for smaller cells compared to larger cells. Typically one assumes by increasing the compression pressure that the contact resistance is decreased and better performance is obtained. However, further increase of compression may cause mass transfer resistance inside of GDL due to the change of physical properties including pore size distribution.

Copolymerization of transition metal salen complexes and conversion into metal nanoparticles supported on hierarchically porous carbon monoliths: a one pot synthesis

Described is the synthesis of metal (Ni, Cr, and Mn) doped macro/mesoporous carbon monoliths by co-polymerization of transition metal complexes with resorcinol/formaldehyde and subsequent pyrolysis. Two salen ligands were synthesized via reaction of ethylene diamine (EDA) and 1,6-diaminohexane (DAH) with 2,4-dihydroxybenzaldehyde to give 4,4′-((1E,1′E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(benzene-1,3-diol) (=E-salen) and 4,4′-((1E,1′E)-(hexane-1,6-diylbis(azanylylidene))bis(methanylylidene))bis(benzene-1,3-diol) (=D-salen). Their metal salen complexes were prepared. All the samples pyrolyzed at 500 °C had macro and mesopores with a specific surface area ranging from 250–500 m2/g. However, the surface area and porosity of the samples decreased dramatically for the metal containing samples pyrolyzed at 800 °C. This is suggested to result from incomplete co-polymerization of the metal salen complexes. The extent of graphitization determined from Raman increased with the pyrolysis temperature. The electrical conductivity was found to increase with the pyrolysis temperature, and followed the trend Ni > Mn > Cr. The M-E-salen containing samples had significantly lower conductivity than their D-salen counterparts.Graphical abstract

Effect of Temperature on Mechanical Property Degradation of Polymeric Materials

Proton Electrolyte Membrane (PEM) fuel cell is a promising energy source because of its high efficiency and zero emission. One of the most important unresolved problems of PEM fuel cells today is the durability issue of its components. For example, the polymeric gasket material of PEM fuel cell must be durable enough to hold the liquid and gas inside the fuel cell channel, as its sealing force decreases gradually with time and also changes with temperature. Liquid Silicone Rubber (LSR) is commonly used as gasket or seal material in many industrial applications including PEM fuel cells. This paper discusses the compression stress relaxation of LSR under temperature cycling, which is to simulate the actual fuel cell operation. It is found that (a) in addition to stress relaxation, thermal expansion or contraction of the material contributes the most in the observed stress variation during temperature change, and (b) the stiffness of LSR appears to change according to temperature history, and (c) the Maxwell stress relaxation model can be used to predict the sealing force only after a correction of the change of material stiffness is implemented into the model.