Locally engineered PEM cells components with optimized operation for improved durability
Data di pubblicazione
Data di priorità
Politecnico di Milano
Department of Energy
Andrea Casalegno, Claudio Rabissi, Laila Grahl-Madsen
Fuel cells are electrochemical devices able to convert chemical energy into electricity by oxidizing a fuel (gaseous, such as hydrogen or liquid such as, for example, methanol) combined with the reduction of oxygen, generating water and electricity. The reverse process takes place in the electrolysis cells. One of the problems with proton-exchange membrane (PEM) fuel cells is limited useful life. Specifically, the operation is characterized by an uneven distribution of current density generation, which tends to increase over time, resulting in a limiting uneven aging of the components.
To optimize local operating conditions and maximize the uniformity of current density in a fuel cell in order to reduce degradation, a gradient of one or more properties (amount, thickness of the catalytic layer or ionomer) of the membrane-electrode assembling (MEA) is used, in combination with a modification of one or more control parameters of the operation (flow, temperature, humidity, or pressure of the oxidant).
For example, it has been shown that by increasing the catalyst load near the inlet and outlet of the air and reducing it to the central areas of a direct methanol PEM fuel cell (DMFC) and slightly increasing the airflow during operation, a reduction of 70% degradation was achieved on a 500-hour basis of operation.
The patented method, therefore, based on the study of the local degradation mechanisms of the components of a fuel cell, allows the design of components of the membrane-electrode assembly with property gradients that, in combination with the optimization of the operating strategy, permits to obtain important results in terms of lifetime improvement.
Campo di applicazione
The invention is applicable in the PEM cell technology-based electric or electrolysis generation industry, either hydrogen-fueled or with fuels such as synthesis gas or liquids as methanol or ethanol.
Sectors in which penetration of the invention is possible are, for example, the distributed or portable stationary generation, as well as industrial and commercial automation, automotive, electrolysis and cogeneration systems, ranging in a wide range of sizes.
The patented method extends the useful life of a fuel cell and improves its performance.