An integrated liquid fuel CPOX reformer and fuel cell system, the integrated system comprising: an array of spaced-apart CPOX reactor units, each CPOX reactor unit comprising an elongate tube having a gas-permeable wall with an internal surface and an external surface, the gas-permeable wall enclosing an open gaseous flow passageway and defining an inlet and an outlet of the CPOX reactor unit, the open gaseous flow passageway being a conduit or channel for the passage of gas therethrough where a solid, including a porous solid or material, is not present across the entire cross-sectional plane of the conduit or channel extending from the inlet to the outlet of the CPOX reactor unit, wherein a CPOX reactor unit is in thermal communication with at least the adjacent CPOX reactor unit(s) in the array, and a CPOX catalyst is disposed within the wall and/or disposed on an internal surface of the wall or partially or completely forms the structure of the wall, wherein a hydrogen barrier is associated with the external surface of at least the CPOX catalyst containing wall section of a CPOX reactor unit; a vaporizer in fluid communication with inlets of the CPOX reactor units; an igniter in thermal communication with the CPOX catalyst-containing wall section of at least one CPOX reactor unit; a fuel cell unit comprising an anode, a cathode, and an electrolyte disposed therebetween, wherein the anode is in fluid communication with the outlet of the CPOX reactor unit and the cathode is in fluid communication with an oxygen-containing gas; and a current collector electrically coupled to the anode and the cathode of the fuel cell unit. an array of spaced-apart CPOX reactor units, each CPOX reactor unit comprising an elongate tube having a gas-permeable wall with an internal surface and an external surface, the gas-permeable wall enclosing an open gaseous flow passageway and defining an inlet and an outlet of the CPOX reactor unit, the open gaseous flow passageway being a conduit or channel for the passage of gas therethrough where a solid, including a porous solid or material, is not present across the entire cross-sectional plane of the conduit or channel extending from the inlet to the outlet of the CPOX reactor unit, wherein a CPOX reactor unit is in thermal communication with at least the adjacent CPOX reactor unit(s) in the array, and a CPOX catalyst is disposed within the wall and/or disposed on an internal surface of the wall or partially or completely forms the structure of the wall, wherein a hydrogen barrier is associated with the external surface of at least the CPOX catalyst containing wall section of a CPOX reactor unit; a vaporizer in fluid communication with inlets of the CPOX reactor units; an igniter in thermal communication with the CPOX catalyst-containing wall section of at least one CPOX reactor unit; a fuel cell unit comprising an anode, a cathode, and an electrolyte disposed therebetween, wherein the anode is in fluid communication with the outlet of the CPOX reactor unit and the cathode is in fluid communication with an oxygen-containing gas; and a current collector electrically coupled to the anode and the cathode of the fuel cell unit.