Polymer electrolyte membranes (PEMs) for fuel cells are chemically degraded by ·OH radicals, generated from H2O2, which is produced by a reaction of hydrogen adsorbed on the Pt anode with O2 diffusing through the PEM. In order to obtain a clue for designing the anode catalyst with low production rate of H2O2 and high activity for the hydrogen oxidation reaction (HOR), we have examined the H2O2 production rate at Pt catalysts as a function of particle size d Pt ranging from 2 nm to 20 nm over a practical temperature range between 20 and 80 °C in 0.1 M HClO4. The H2O2 production rate [per geometric area with 1.5 to 2-layer height of catalyst layer] was found to decrease with increasing d Pt, accompanied by a penalty of decreased mass activity for the HOR. The use of Pt skin-covered PtCo/C is shown to be an attractive potential solution, providing a breakthrough in simultaneously achieving low H2O2 production and high HOR activity.

Polymer electrolyte membranes (PEMs) for fuel cells are chemically degraded by the attack of •OH radicals generated from the decomposition of H 2 O 2 , which is predominantly produced at the Pt/C hydrogen anode. The incorporation of conventional radical scavengers into the PEM suffers from a decrease in the output performance. We, for the first time, demonstrate that the addition of hygroscopic silica nanoparticles (NPs) to the Pt/C anode catalyst layer provides a remarkably prolonged (ca. 4 times) lifetime of a Nafion membrane in an accelerated stress test and open circuit voltage (OCV) holding at 90 °C, accompanied by improved output (I−E) performances at low relative humidity. It has been found that the use of silica NPs decreases H 2 O 2 formation rate from the OCV to a practical H 2 oxidation potential in a half-cell using 0.1 M HClO 4 at 90 °C and provides reduced ohmic resistance (increase in water content) and effective utilization of Pt cathode catalyst in a single cell, by which the improvement of the durability of the PEM and increased output performance are explained rationally.

Palladium (Pd) octahedral and spherical nanocrystals (NCs) were successfully synthesized on crumpled graphene oxide (GO) by surface adsorption of H2 and CO in the presence of capping agent poly(vinylypyrrolidone) (PVP). Their comparative studies as anode material for direct methanol fuel cells (DMFCs) have been measured by hydrogen evolution reaction (HER) performance and methanol oxidation reaction (MOR) activity. The electrocatalytic properties of both the nanocrystals were studied in HClO4 acidic media and com-pared with each other. Pd octahedral nanocrystals have shown the best performance as an anode material, their onset potential for evolu-tion of hydrogen from the active sites of the catalyst is more towards zero than the spherical NCs. The observed specific activity (ca. 4.3 mA.cm-2) and mass activity (ca. 5300 mA.mg-1) of Pd towards MOR is much higher for octahedral NCs than that of spherical NCs.

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