Thermal Stability in Air of Pt/C Catalysts and PEM Fuel Cell Catalyst Layers

Abstract

The durability of PEM fuel cell materials is essential to application longevity. This research explores the limits of thermal stability of platinum/Vulcan XC 72 catalysts and a 46 wt % Pt/Vulcan XC 72/Nafion catalyst layer. The thermal stability of Pt/Vulcan XC 72 catalysts and the PEM fuel cell catalyst layer is studied by thermal gravimetric analysis (TGA) in air. The products of decomposition are analyzed with TGA coupled with mass spectrometry (TGA−MS). Low temperature (100−200 °C) carbon combustion in the presence of platinum is confirmed. The high precision and sensitivity of TGA allows differentiation of two oxidative/mass loss regimes for 46% Pt/C. The presence of surface protective groups raises the activation energy for the low-temperature/low-conversion (≤5%) oxidation of 46% Pt/Vulcan XC 72 (197 ± 13 kJ/mol) compared to a higher temperature/higher conversion level (10−30%) process (140 ± 10 kJ/mol). In PEM fuel cell catalyst layers, the thermal decomposition temperature of Nafion is lowered by about 100 °C to 300 °C in the presence of Pt/C catalysts. As a result of the above studies it was found that TGA is convenient for the determination of Pt wt % in catalyst-coated membranes.

Influence of Particle Size on the Properties of Pt–Ru∕C Catalysts Prepared by a Microemulsion Method

“…In the third region, an abrupt mass loss commences at around 300°C, and at temperatures of about 470°C all the carbon initially present was lost and the mass reached a constant value very close to the 20% nominal metal load. In a general manner, TGA curves were very similar to those reported by Baturina et al 27 for the thermal decomposition in air of Pt/C samples. Even assuming complete oxidation of all the Pt and Ru in these catalysts to form PtO and RuO 2 , which would involve a mass gain of ca.…”

The Use of C-MnO2 as Hybrid Precursor Support for a Pt/C-MnxO1+x Catalyst with Enhanced Activity for the Methanol Oxidation Reaction (MOR)

“…In fact, according to the literature [27][28][29], in inert atmosphere at around 500 °C MnO2 is reduced to Mn2O3 and further reduced to Mn3O4 at 900 °C. These results are in line with the presence of the mixture of hausmannite and bixbyite manganese oxides on the final Pt/C-MnxO1+x catalyst, annealed at 600 °C in nitrogen atmosphere, as pointed out by XPS analysis.…”

Improving the Ethanol Oxidation Activity of Pt-Mn Alloys through the Use of Additives during Deposition

“…Five distinctive mass loss regions are observed in Figure 1. The mass loss between 100 °C and 250 °C was attributed to the thermal decomposition of residual, weak carbon functional groups and water evaporation in the powders [29,30]. A second major mass loss began at 300 °C, which was related to the oxidation of carbon black by the oxygen or the air trapped within the powder particles [30].…”