Catalytic and DRIFTS study of the WGS reaction mechanism on Pt-based catalysts

CH. VIGNATTI; C.R.APESTEGUÍA; TERESITA F. GARETTO

Lyon

Congreso; 4 Natural gas Congress; 2010

Water gas shift (WGS) conversion, CO + H2O ® CO2 + H2, is a crucial reaction in the production of hydrogen for fuel cell applications. Conventional Cu-based catalysts do not meet the strict requirements for onboard polymer electrolyte fuel cells. More active noble metal catalysts, in particular Pt-based catalysts, have been lately investigated for developing an efficient single-stage WGS conversion technology. Results have shown that the Pt activity for the WGS reaction greatly depend on the reducibility of support but knowledge on the mechanism requirements for optimizing the activity and stability of Pt-based catalysts is still lacking. Depending on the support, the WGS reaction on Pt may proceed via the redox mechanism or the formate associative mechanism, although a hybrid associative mechanism with redox regeneration has also been proposed to account for the WGS reaction on Pt/ZrO2 catalysts [1]. In all the cases, the two reactants for WGS reaction, CO and H2O, need to be activated. Cu-based catalysts may promote the WGS reaction on copper via a redox mechanism [2], but for Pt-supported catalysts the presence of a hydrophilic support would be necessary to adsorb and activate water. Thus, to improve the activity of Pt-based catalysts via a bifunctional mechanism it would be essential to promote the interaction and cooperation between the metallic crystallites and the surface active sites of the support. In this work, we have studied the WGS reaction on Pt supported on reducible and non-reducible supports, namely Pt/SiO2, Pt/CeO2, and Pt/TiO2 catalysts, by in-situ diffuse reflection infrared spectroscopy (DRIFTS). The aim was to gain insight on the WGS reaction mechanism on Pt-based samples using in-situ DRIFTS technique