Transition metals

A notable example is Iron in the Haber process, for producing ammonia.

whts transition metals act as catalysts??

homogeneous catalysts are catalysts that are in the same state as the reactants
eg
Fe 2+ and Fe 3+ in the following reaction
Fe^3+ + I2 = Fe^2+ + 2I^-
Fe^2+ + S2O8^2- = Fe^3+ + 2SO4^2-

so simply it means that the transition metal acting as a catalyst change its oxidation state so that reactants are converted into products then the transition metals again change oxidation state and are brought back to thier initial oxidation state..

yep!
thats actually the very definition of a catalyst
its a molecule that speeds up the rate of a reaction by providing an alternate route with lower activation energy and remains unchanged itself by the end of the reaction,

Its the same
But the diff is that in heterogeneous catalyst the enzyme is in a diff state than the reactants eg in Haber process the catalyst, iron, is solid but the reactants, hydrogen and nitrogen, are gaseous

i think that in heterogeneous they reactants are adsorbed on the surface of solid then thier bonds are weakened hence the activation energy decreases