Mechanism of aging for a Pt/CeO2-ZrO2 water gas shift catalyst

An investigation of the practical viability of Pt on CeO2-containing supports as water gas shift catalysts is reported. This paper takes into account the anticipated duty cycles for residential fuel processors integrated to a PEM fuel cell.It was recently found that CeO2 based catalysts deactivate upon start–stop operation of fuel processors due to carbonate build-up and we suggested that ZrO2-CeO2 composites may be a better choice as the support.Aging of Pt-based ZrO2-CeO2 supported WGS catalysts however is observed under relatively mild operating conditions. We investigated the reasons for aging observed under steady-state operation, high temperature stress and start–stop cycling for a Pt/CeO2-ZrO2 water gas shift catalyst by activity testing, transmission electron microscopy (TEM), IR and chemisorption techniques. Substantial aging was observed under both steady-state operation at relatively low temperature (200–250 °C) and high temperature stress (up to 450 °C), whereas almost no reduction in activity was seen by simulating start–stop cycling, unlike with Pt/CeO2.The loss of activity could be correlated with Pt dispersion measured by CO chemisorption and TEM. Very little formation of hydroxycarbonate and carbonates on the ceria part of the support was observed.