Dzmitry Malevich

Electrochemical Activity and Catalyst Utilization of Low Pt and Thickness Controlled Membrane Electrode Assemblies

An improved catalyst deposition methodology based on a piezo-electric printing technique has been developed and used to fabricate catalyst coated membranes (CCM) with thin catalyst layers (1-5 μm) and ultra-low Pt loadings (0.02-0.12 mg Pt /cm 2 ). The performance of these CCMs was examined in proton exchange membrane fuel cells (PEMFCs). The catalyst utilization was observed to increase with decreasing catalyst layer thickness (decreasing Pt loading). The printed CCM with two layers containing an ultra-low Pt loading (0.02 mg Pt /cm 2 ) exhibited Pt utilizations of 100%. Neglecting the anode contributions, the mass activity at 850 mV for the printed CCM is nearly 76.5 mA/mg Pt which is 3.5 times higher than that for the CCM fabricated by conventional spraying method (22.5 mA/mg Pt ).

Effect of Relative Humidity on Electrochemical Active Area and Impedance Response of PEM Fuel Cell

The influence of humidity of supplied gases on on electrochemically active surface area and charge transfer resistance in cathode process of PEM fuel cell was studied. Impedance spectra for cells operated with various gas stream combinations - H2/Air, H2/O2, H2/H2 and H2/N2 - was analyzed to determine the physical/chemical origin of the spectra features. Cathode charge transfer resistance increased with a decrease in the humidity of supplied gases. As well, a reduction in the electrochemically active surface area with a decrease in relative humidity was observed.

Preparation of Ultra-Thin Catalyst Layers by Piezo-electric Printer for PEMFCs Applications

Introduction One of the main technical barriers to commercialization of Proton Exchange Membrane Fuel Cells (PEMFCs) operated at low temperatures (up to 90 °C) is the material cost, which is in major part attributed to the cost of platinum metal [1]. From the perspective of electrode performance, the cost problem can be tackled in two ways: reduction of the catalyst loading and improvement of the catalyst utilization and performance. Electrodeposition and sputter deposition have been used to manufacture membrane-electrode assemblies (MEAs) of low catalyst loadings [2-4]. However, these techniques have several drawbacks to overcome, including film homogeneity/size of the particle deposited and MEA life time. Theoretical studies have shown that the utilization of the Pt catalyst in these thicker films is low and desirable performance can be attained without using high amounts of platinum if thin catalyst layers are used wherein the catalytic utilization of platinum is higher. The objective of this work is to present an improved catalyst deposition methodology, based on a piezo-electric printing technique [5], that can overcome many of the current limitations and that can to produce MEAs having (i) very low precious metal (Pt) loading and (ii) better utilization of the precious metal present on the electrode in PEMFCs. This procedure for manufacturing catalyst coated membrane (CCM) resulted in the enhanced performance of state-of-the-art experimental fuel cells.

On the Determination of PEM Fuel Cell Catalyst Layer Resistance from Impedance Measurement in H2/N2 Cells

Impedance measurements of H2/N2 cell for the determination of PEMFC catalyst layer (CL) resistance can exhibit significant deviation from those predicted assuming homogeneous CL structure with uniform resistance and capacitance. Predictions from model with homogeneous structure but distributed resistance and/or capacitance shows deviation from the ideal mid-frequency response (45o line) but expected low-frequency response (vertical line). A distributed model considering agglomerate-type structure shows deviation from ideal mid-frequency response ((45o line) as well as from ideal vertical-line like response at experimentally employed frequencies although a vertical-line response is predicted at frequencies significantly lower than typically accessible in experiments.