The Effect of Precursor Concentration on the Crystallite Size of CeO₂ to Enhance the Sulfur Resistance of Pt/CeO₂ for Water Gas Shift

To develop customized sulfur–resistant catalysts for the water gas shift (WGS) reaction in the waste–to–hydrogen process, the effects of changing the nucleation conditions of the CeO₂ support on catalytic performance were investigated. Supersaturation is a critical kinetic parameter for nuclei formation. The degree of supersaturation of the CeO₂ precipitation solution was controlled by varying the cerium precursor concentration from 0.02 to 0.20 M. Next, 2 wt.% of Pt was impregnated on those various CeO₂ supports by the incipient wetness impregnation method. The prepared samples were then evaluated in a WGS reaction using waste–derived synthesis gas containing 500 ppm H₂S. The Pt catalyst supported by CeO₂ prepared at the highest precursor concentration of 0.20 M exhibited the best sulfur resistance and catalytic activity regeneration. The sulfur tolerance of the catalyst demonstrated a close correlation with its oxygen storage capacity and easier reducibility. The formation of oxygen vacancies in CeO₂ supports is promoted by the formation of small crystals due to a high degree of supersaturation.