Mesoporous platinum as sulfur-tolerant catalyst for PEMFC cathodes

Abstract

The performance of proton exchange membrane fuel cell (PEMFC) is highly influenced by its operating conditions. One of the vital parameter is the purity of feed gases. The cathode of PEMFC is normally fed with air from the atmosphere containing certain impurities like CO2, NO2, and SO2, which are the major contaminants for the electrocatalysts used in the fuel cell, causing both reversible and irreversible damages. The irreversible effect is caused due to adsorption of impurities like SO2 on the conventionally used platinum catalyst supported on carbon (Pt/C). It has been observed that carbon facilitates the absorption of SO2 on platinum. Hence, the present objective is to identify the catalysts containing no carbon and study their impurity tolerance in the fuel cell environment. In the present paper, we have attempted to synthesize unsupported mesoporous platinum by hard template method and studied its SO2 impurity tolerance at the cathode side for oxygen reduction reaction (ORR) for PEMFC application. The mesoporous platinum showed for a higher tolerance towards SO2 compared to its counterpart, viz., platinum black. Sulfur tolerance was evaluated by the sulfur coverage on the catalyst and its rate of recovery through electrochemical experiments. Mesoporous platinum has also exhibited a faster removal of adsorbed sulfur compared to the commercial microporous platinum black, revealing that the recovery is also fast comparatively for meso-structured platinum.