Activity and Stability of Dispersed Multi Metallic Pt-based Catalysts for CO Tolerance in Proton Exchange Membrane Fuel Cell Anodes

Abstract

Studies aiming at improving the activity and stability of dispersed W and Mo containing Pt catalysts for the CO tolerance in proton exchange membrane fuel cell (PEMFC) anodes are revised for the following catalyst systems: (1) a carbon supported PtMo electrocatalyst submitted to heat treatments; (2) Pt and PtMo nanoparticles deposited on carbon-supported molybdenum carbides (Mo2C/C); (3) ternary and quaternary materials formed by PtMoFe/C, PtMoRu/C and PtMoRuFe/C and; (4) Pt nanoparticles supported on tungsten carbide/carbon catalysts and its parallel evaluation with carbon supported PtW catalyst. The heat-treated (600 oC) Pt-Mo/C catalyst showed higher hydrogen oxidation activity in the absence and in the presence of CO and better stability, compared to all other Mo-containing catalysts. PtMoRuFe, PtMoFe, PtMoRu supported on carbon and Pt supported on Mo2C/C exhibited similar CO tolerances but better stability, as compared to as-prepared PtMo supported on carbon. Among the tungsten-based catalysts, tungsten carbide supported Pt catalyst showed reasonable performance and reliable stability in comparison to simple carbon supported PtW catalyst, though an uneven level of catalytic activity towards H2 oxidation in presence of CO is observed for the former as compared to Mo containing catalyst. However, a small dissolution of Mo, Ru, Fe and W from the anodes and their migration toward cathodes during the cell operation is observed. These results indicate that the fuel cell performance and stability has been improved but not yet totally resolved.

Carbon Monoxide Tolerant Pt-Based Electrocatalysts for H2-PEMFC Applications: Current Progress and Challenges

“…Hassan and co-workers [73] followed the opposite path, i.e., increasing the alloying degree of PtMo/C by including a heat treatment step (600 • C for 1 h under H 2 atmosphere) in the formic acid reduction synthesis method. It was found that the heat-treated catalyst (denoted as PtMo/C-ht) presented both higher CO tolerance (Figure 4d) under 100 ppm CO poisoning and higher stability compared to the corresponding untreated catalyst.…”

“…The authors [73] attributed the improved CO tolerance and stability to the higher alloying degree induced by the heat treatment under H 2 atmosphere. Previous studies have demonstrated that heat treatment under the forceful reducing H 2 atmosphere causes sufficient reduction of metal salts, resulting in a high alloying degree and large ratio of metallic/oxide catalyst surface states [74].…”

“…We have seen [70,73,106,127] that the inclusion of Mo and W enhances the CO tolerance through the bifunctional mechanism, which is ascribed to their redox properties. In this manner, Mo and W oxide and carbide composites have recently been explored as supports for CO-tolerant electrocatalysts.…”

“…(d) Polarization curves for H2 and 100 ppm CO/H2 feed at 85 °C. Data obtained from[73]. (e) On-line mass spectrometry results at the anode outlet at 85 °C for H2 and 1000 ppm CO/H2 feed at OCV and (f) CV results of AST at 25 °C and 50 mV s −1 for various cycles.…”

Rapid synthesis of highly active Pt/C catalysts with various metal loadings from single batch platinum colloid

“…They can be used for almost all fuel cell powered vehicles and some other commercial devices due to their high activity at relatively low operation temperature and their excellent stability under strongly acidic environment and in intense electromagnetic field [8] . Although binary [9] , ternary [10] and even quaternary [11] Pt-based electrocatalysts have been introduced to replace Pt/C catalyst for the cathode of PEMFC, it is a very effective way to start with classic Pt/C system for proving a new concept during the new method development of catalyst preparation. To improve Pt utilization efficiency and the balance control of water and heat, high metal-loading Pt/C electrocatalysts (around or over 50 wt%) are preferred to allow the fabrication of thin-layer MEA [12] .…”