Engineering Cobalt‐Based Thin Films for Fischer–Tropsch Synthesis

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ABSTRACT We report on the synthesis of cobalt‐based thin films via magnetron sputtering at varying conditions, including sputtering pressure, reactive gas composition, substrate temperature, and post‐deposition annealing. The produced thin films exhibit diverse morphologies, crystalline phases, and oxidation states, such as metallic cobalt (Co 0 ) and cobalt oxides (CoO and spinel‐Co 3 O 4 ). Two thin‐film catalyst architectures, based on Co 0 (TFCat1) and Co x O y (TFCat2), on Si/Al 2 O 3 /SiO 2 support stacks are further developed as analogues of commercial powder‐based Fischer–Tropsch synthesis (FTS) catalysts. The phase evolution in both of these model catalyst systems is investigated in situ under FTS‐relevant reduction conditions using synchrotron‐based grazing‐incidence x‐ray diffraction. Both catalysts (TFCat1 and TFCat2) were tested for their FTS catalytic performance at comparable operating conditions. A lined‐out CO conversion level of ca . 4.6% and 4.9% was obtained for TFCat1 and TFCat2, respectively. These catalysts exhibited distinct steady‐state product distributions: TFCat1 showed enhanced selectivity toward kerosene‐range hydrocarbons, while TFCat2 produced a wider hydrocarbon distribution extending to C 27 . Moreover, Cobalt thin‐film model catalyst (TFCat1) shows significantly reduced dewetting compared to its oxide counterpart (TFCat2) under FTS operating conditions. The well‐defined and easy to tune cobalt‐based thin films provide a robust foundation for the rational scale‐up of next‐generation catalysts.

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