Catalytic properties of bimetallic catalyst for methanol steam reforming

Abstract

Methanol steam reforming is an attractive route to on-board H$_2$ production for fuel cell vehicles, except for the problem of CO byproduct poisoning the fuel-cell electrode. Herein, we show that the CO generation can be lowered remarkably when the reforming reaction is carried out over a bimetallic PdIn catalyst supported on nanoporous silica gel. The Pd-In/silica was prepared by following a conventional impregnation process using aqueous solution of tetraamminepalladium and indium nitrates simultaneously. The In/Pd molar ratio was varied over 0 ~ 4 at a fixed Pd loading of 2 wt%. Among the Pd-In samples prepared in this manner, the sample with In/Pd = 2.5 exhibited the best catalytic performance with negligible CO production at 300 °C, which was superior to that of Pd-In/γ-alumina or Pd-In/MCM-48 mesoporous silica of the same metal loading. Characterization of this catalyst by atomic-resolution transmission electron microscopy indicated that the low CO generation (i.e., high CO$_2$/CO selectivity) is due to the formation of Pd1In1 intermetallic compound-type alloy nanoparticles. Temperature-programmed reduction of the catalytic metal precursors with H2 suggested that the alloy formation could be promoted by the surface silanol groups existing on silica.