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Hydrogen spillover has been invoked to explain the functioning of platinum as a promoter in cobalt-based Fischer–Tropsch catalysts. In this study, the operation of Pt was investigated using a model hybrid catalyst (i.e. mixture of Pt/Al₂O₃ + Co/Al₂O₃) which allowed for decoupling of hydrogen spillover effects from those requiring direct Pt–Co contact. Pt improved the reducibility of the hybrid catalyst despite physical separation of Pt from Co.

TPR, TGA, in situ XRD and quasi in situ XPS confirmed that supported Co₃O₄ reduced via formation of CoO as a stable intermediate. Pt had only a slight effect on Co₃O₄ → CoO reduction, but greatly improved the CoO → Co⁰ reduction which was severely hindered by interaction with the alumina support. The catalysing effect of Pt on the reduction was attributed to H₂ dissociation and its subsequent spillover occurring more readily than direct H₂ activation by the cobalt oxides …