Ti ₀. ₉₇Pd ₀. ₀3O ₂− δ was coated on γ -Al ₂O ₃-coated honeycomb structured cordierite monolith (AHCM) by solution combustion method using dip-dry-heat process. This is a modified conventional method to coat the catalysts on honeycomb structured cordierite monolith (HCM). Formation of Ti ₀. ₉₇Pd ₀. ₀3O ₂− δ on AHCMwas confirmed by XRD. The XPS spectra of Pd(3d) core level confirmed Pd ion in Ti ₀. ₉₇Pd ₀. ₀3O ₂− δ is in the form of +2 state.The surface morphology of coated catalystwas unchanged by long time exposure to hydrogencombustion reaction; i.e., H ₂ +O ₂ recombination reaction which indicated the stability of coating on monolith. Ti ₀. ₉₇Pd ₀. ₀3O ₂− δ showed high rates of H ₂ + O ₂ recombination compared to 2 atom% Pd(metal)/γ -Al ₂O ₃, Ce ₀. ₉₈Pd ₀. ₀ ₂O₂− δ ,Ce ₀. ₉₈Pt ₀. ₀ ₂O₂− δ Ce ₀. ₇₃Zr ₀. ₂₅Pd ₀. ₀ ₂O₂− δ, Ti ₀. ₉₉Pd ₀. ₀ ₁O₂− δ and Ti ₀. ₉₈Pd ₀. ₀ ₂O₂− δ. The activation energy of H ₂ + O ₂ recombination reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂− δ is 7.8 kcal/mol. The rates of reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂− δ at 60◦C are in the range between 10 and 20 μmol/g/s. The rate of reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂− δ increased with increase in the concentration of H ₂. For 50 mL of H ₂, it showed rates of the reaction around 36.45 μmol/g/s at room temperature and 230 μmol/g/s at 60◦C. It was found that the rate of reaction due was lower due to hindering effect by adsorption of other gas molecules on the catalytic site.Finally, we propose a mechanism of hydrogen and oxygen recombination reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂− δ.
Volume 134, 2022
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