Efficient hierarchically structured composites containing cobalt catalyst for clean synthetic fuel production from Fischer–Tropsch synthesis

•TiO2-coated CNTs decorated on α-Al2O3 hierarchical structure is synthesized.•The as-prepared hierarchical catalyst presents high Fischer–Tropsch (FTS) activity.•Excellent FTS rate up to 0.80gC5+gcat−1h−1 along with high stability is obtained.•Zero field 59Co NMR is used to understand catalyst structure–activity relationship.•Cobalt particles with size <10nm are the most abundant in hierarchical catalyst.