Influence of carrier effect on Pd/Al₂O₃ for methane complete catalytic oxidation

Pd/Al₂O₃ catalysts modified by different chemical elements (Mg, Si, Ce, and Zr) were tested for methane (CH₄) catalytic combustion, and PdO nanoparticles loaded on modified Al₂O₃ were systematically studied. These conditions assess the carrier effects of Pd/Al₂O₃ and acid strength influences on CH₄ combustion. We observed carrier effects on activation energy through tuning Pd 3d binding energies (BEs) and on pre-exponential factors (A) through Pd dispersion and acidity on supports. When the BE of Pd 3d_5/2 is 337.3 eV, PdO nanoparticles loaded on modified Al₂O₃ have excellent activity in cracking the C-H bond of CH₄, which leads to the lowest activation energy (E ), regardless of the size effect of the PdO nanoparticle. Furthermore, a theoretical construction that acid sites on catalysts promote the reversible elementary step (2Pd-OH ↔ Pd-O* + Pd* + H₂O) right shifts improving the A dependency on the quantity of exposed Pd* and Pd-O*. As a result, Al₂O₃, as the carrier, not only modifies the electronic characteristics and size of supported PdO nanoparticles but also participates in the reaction process via acid sites on the surface of Al₂O₃.