Promotive effect of boron oxide on the iron-based catalysts for Fischer-Tropsch synthesis

•The dispersion of iron species is greatly enhanced by B2O3.•The interaction between iron and boron render the electron deficiency of iron species.•The promotion of B2O3 result in higher tendency to H2 rather than CO for doped catalysts.•B2O3 greatly inhibit the coke deposition of catalysts and promotes the hydrogenation activity of catalyst.