Performance of a NiFe(2)O(4)@Co Core–Shell Fischer–Tropsch Catalyst: Effect of Low Temperature Reduction

[Image: see text] In situ TEM gas-cell imaging and spectroscopy with in situ XRD have been applied to reveal morphological changes in NiFe(2)O(4)@Co(3)O(4) core–shell nanoparticles in hydrogen. The core–shell structure is retained upon reduction under mild conditions (180 °C for 1 h), resulting in a partially reduced shell. The core–shell structure was retained after exposing these reduced NiFe(2)O(4)@Co(3)O(4) core–shell nanoparticles to Fischer–Tropsch conditions at 230 °C and 20 bar. Slightly harsher reduction (230 °C, 2 h) resulted in restructuring of the NiFe(2)O(4)@Co(3)O(4) core–shell nanoparticles to form cobalt islands in addition to partially reduced NiFe(2)O(4). NiFe(2)O(4) underwent further transformation upon exposure to Fischer–Tropsch conditions, resulting in the formation of iron carbide and nickel/iron–nickel alloy. The turnover frequency in the Fischer–Tropsch synthesis over NiFe(2)O(4)@Co(3)O(4) core–shell nanoparticles reduced in hydrogen at 180 °C for 1 h was estimated to be less than 0.02 s(–1) (cobalt-time yield of 8.40 μmol(.)g(-1.)s(–1)) with a C(5+) selectivity of 38 C-%. The low turnover frequency under these conditions in relation to the turnover frequency obtained with unsupported cobalt is attributed to the strain in the catalytically active cobalt.