Low-Pt loading cathode modified with Keggin type Cs-salt polyoxometalate as co-catalyst for PEM-Fuel Cells

The catalytic activity of Pt particles mixed with mesoporous Keggin-type polyoxometalate Cs3H2PMo10V2O40 towards oxygen reduction reaction is explored. Polyoxometalates are attractive due to their properties to strong adsorb metal catalyst inside the micro-mesopores and their high acidity, enhancing ORR kinetics and durability [1]. The polyoxometalate co-catalyst are prepared by titration of an aqueous solution of phosphovanadomolibdic acid [2]. SEM micrography shows reduction particle size to less than 300nm after synthesis and XRD confirms the Keggin-type structure. The composite catalyst is prepared by mixing the POM salt with Pt/C by sonication. RRDE studies show better kinetics for ORR with low Pt loading at the electrode surface. A MEA is assembled by using a Pt/POM-based cathode, in order to assess performance in a working fuel cell [3]. Polarization study reveals comparable or better performances behavior at 100%, 62% and 17% relative humidity (RH) for the POM-modified MEA with respect to a commercial MEA with higher Pt loading at the cathode. Finally, an accelerated stress test (AST) with square wave (SW) between 0.4 V and 0.8 V is performed to evaluate MEA stability for at least 100 h and make predictions about lifetime.