A reformer module (10) comprises a hollow support member (12) having at least one passage (14) extending longitudinally therethrough. The hollow support member (14) has an external surface (20), a barrier layer (22) arranged on at least a portion of the external surface (20) of the hollow support member (12), a catalyst layer (24) arranged on the barrier layer (22) and a sealing layer (26) arranged on the catalyst layer (24) and the external surface (20) of the hollow support member (12) other than the at least a portion of the external surface of the hollow support member (12). By providing the barrier layer (22) and the catalyst layer (24) on the exterior surface (20) of the hollow support member (12), the distribution of the barrier layer (22) and/or the catalyst layer (24) may be more precisely controlled and thus a non-uniform distribution of barrier layer (22) and/or catalyst layer (24) may be achieved.