Platinum Alloy Electrocatalysts with Enhanced Resistance to Anion Poisoning for Low and Medium Temperature Fuel Cells

Institute Reference: INV-0863

Background

Proton exchange membrane (PEM) fuel cells are useful due to their high energy density, high efficiency, relatively low operating temperature and low emission of pollutants. However, low performance of the oxygen reduction reaction (ORR) at the cathode is a principle obstacle to the successful application of PEM fuel cells, particularly in transportation. Various Pt based alloy catalysts have been developed and show enhanced catalytic activity compared to Pt/C towards oxygen reduction reaction in PEM fuel cells, and also in phosphoric acid fuel cells that operate at higher temperatures. Nevertheless, in most of the methods for the preparation of carbon supported Pt-based alloy catalysts, high temperatures are required to form the alloy, resulting in a lower catalyst active area. Another disadvantage of such methods is that the Pt and other transition metals may deposit separately on the carbon support, rather than in close association.

Technology Overview

This Northeastern University invention provides a catalyst for use in electrochemical applications. The catalyst is made from nanoparticles containing an alloy of platinum and one or more transition metals. The method includes reducing platinum and the transition metals in the presence of a surfactant, i.e., in a micellar environment. The resulting nanoparticles then can be attached to carbon particles and used, for example, as a coating material for preparing a fuel cell cathode. The platinum alloy catalyst of the invention is uniform in size and monodisperse, resulting in superior electrochemical properties for use in low and medium temperature fuel cells, such as phosphoric acid fuel cells.

The electro-catalyst:

• Results in a greater resistance to surface poisoning from anions present in acid-electrolytes, especially for low and medium temperature fuel cells

• Enables a significant enhancement of oxygen reduction reaction with improved associated performance

• Allows for improved economies of scale with enhanced commercial acceptance

• Allows for a controlled surface morphology as compared to conventional catalysts

• Enables an effective lowering of platinum dissolution, and enhanced anion free platinum surfaces

Benefits

The advantages of this invention over prior art include:

Lowering of over potential of oxygen reduction reaction by approximately 100‑150mV. This in turn results in higher ORR activity
Lowering of dissolution of Pt at open circuit conditions when operated at typical PAFC condition of 150 to 200°C
Significantly higher monodipersity and controlled morphology for lower sintering of supported crystallites under actual fuel cell operating conditions