Methane combustion over Pd/CoAl2O4/Al2O3 catalysts prepared by galvanic deposition

Abstract

Pd/CoAl₂O₄/Al₂O₃ methane combustion catalysts were synthesized using a galvanic deposition (GD) method (PdCoAl-GD). This PdCoAl-GD catalyst showed higher activities and turnover frequencies (TOFs) than conventional Pd/Al₂O₃. According to X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and scanning transmission electron microscopy (STEM) measurements, PdCoAl-GD was composed of a CoAl₂O₄ phase supported on γ-Al₂O₃ and dispersed Pd nanoparticles of 2–7 nm in size on CoAl₂O₄. Operando Pd K-edge XAFS measurements indicated that the Pd in PdCoAl-GD was oxidized to highly active methane combustion PdO species at low temperatures. PdCoAl-GD also showed high activity (light-off tests) when PdO was initially present on the catalysts. Methane temperature-programmed reaction (CH₄-TPR) measurements on PdCoAl-GD revealed that PdO was reduced by CH₄ at low temperatures. The GD method used herein achieved PdO species that were effective for C–H activation.