Systems and methods are provided for using fuel cell staging to reduce or minimize variations in current density when operating molten carbonate fuel cells with elevated CO.sub.2 utilization. The fuel cell staging can mitigate the amount of alternative ion transport that occurs when operating molten carbonate fuel cells under conditions for elevated CO.sub.2 utilization.

Systems and methods are provided for maintaining and/or improving operating lifetime for molten carbonate fuel cells that contain reforming catalyst in the anode when processing cathode input flows that contain sulfur oxides. The systems and methods can include a serial arrangement of molten carbonate fuel cells, where a first fuel cell includes a reduced or minimized amount of reforming catalyst in the anode. A second molten carbonate fuel cell can include reforming catalyst in the anode.

A method for capturing carbon dioxide comprises introducing a first feed stream comprising carbon dioxide and dioxygen into a first electrochemical cell, reducing the carbon dioxide to carbonate ions at a first cathode of the first electrochemical cell, and reducing the carbonate ions at a first anode to produce a first product stream comprising concentrated carbon dioxide and a second product stream comprising water. A second feed stream comprising water is introduced to a second electrochemical cell coupled to the first electrochemical cell. The water is oxidized at a second anode of the second electrochemical cell to produce hydrogen ions and dioxygen gas, the hydrogen ions are reduced to hydrogen gas at a second cathode, and the hydrogen gas produced by the second cathode is transported to the first anode. The first product stream is removed from the first electrochemical cell. Additional methods and related systems are also disclosed.

A layered cathode structure for a molten carbonate fuel cell is provided, along with methods of forming a layered cathode and operating a fuel cell including a layered cathode. The layered cathode can include at least a first cathode layer and a second cathode layer. The first cathode layer can correspond to a layer that is adjacent to the molten carbonate electrolyte during operation, while the second cathode layer can correspond to a layer that is adjacent to the cathode collector of the fuel cell. The first cathode layer can be formed by sintering a layer that includes a conventional precursor material for forming a cathode, such as nickel particles. The second cathode layer can be formed by sintering a layer that includes a mixture of particles of a conventional precursor material and 1.0 vol % to 30 vol % of particles of a lithium pore-forming compound. The resulting layered cathode structure can have an increased pore size adjacent to the cathode collector to facilitate diffusion of CO.sub.2 into the electrolyte interface, while also having a smaller pore size adjacent to the electrolyte to allow for improved electrical contact and/or reduced polarization at the interface between the electrolyte and the cathode.

A molten carbonate fuel cell assembly includes a cathode electrode; an anode electrode; an electrolyte matrix disposed between the cathode electrode and the anode electrode; a cathode current collector abutting the cathode electrode; and a first electrolyte composition stored in the cathode electrode, the first electrolyte composition comprising a first mixture of a eutectic Li/Na carbonate electrolyte doped with one or more additive materials, wherein the one or more additive materials comprise one or more of SrO, BaCO.sub.3, BaO, SrCO.sub.3, and combinations thereof.

A fuel cell system includes a fuel cell having a cathode and an anode configured to receive a portion of a hhydrocarbon feed and to output an anode exhaust stream comprising carbon dioxide, hydrogen, and water; and an electrolyzer cell having a cathode and an anode. The anode of the electrolyzer cell is configured to receive a first portion of the anode exhaust stream and another portion of the hydrocarbon feed, and to generate a hydrogen stream.

Molten carbonate fuel cells (MCFCs) are operated at elevated pressure to provide increased operating voltage and/or enhanced CO.sub.2 utilization with a cathode input stream having a low CO.sub.2 content. It has been discovered that increasing the operating pressure of a molten carbonate fuel cell when using a low CO.sub.2-content cathode input stream can provide unexpectedly large increases in operating voltage while also reducing or minimizing the amount of alternative ion transport and/or enhancing CO.sub.2 utilization.

Disclosed here is a supported catalyst comprising a thermally stable core, wherein the thermally stable core comprises a metal oxide support and nickel disposed in the metal oxide support, wherein the metal oxide support comprises at least one base metal oxide and at least one transition metal oxide or rare earth metal oxide mixed with or dispersed in the base metal oxide. Optionally the supported catalyst can further comprise an electrolyte removing layer coating the thermally stable core and/or an electrolyte repelling layer coating the electrolyte removing layer, wherein the electrolyte removing layer comprises at least one metal oxide, and wherein the electrolyte repelling layer comprises at least one of graphite, metal carbide and metal nitride. Also disclosed is a molten carbonate fuel cell comprising the supported catalyst as a direct internal reforming catalyst.

Systems and methods are provided for using fuel cell staging to reduce or minimize variations in current density when operating molten carbonate fuel cells with elevated CO.sub.2 utilization. The fuel cell staging can mitigate the amount of alternative ion transport that occurs when operating molten carbonate fuel cells under conditions for elevated CO.sub.2 utilization.

A fuel cell system includes a fuel cell unit configured to generate an amount of electrical power for supply to a varying electrical load and a fuel cell controller configured to receive a first indication that the varying electrical load is at a local maximum within a predetermined period, and, in response, operate the fuel cell unit with an operational parameter having a first value such that the fuel cell unit produces a limited maximum amount of electrical power that is a predetermined percentage of a maximum rated power output of the fuel cell unit. The fuel cell controller is also configured to receive an indication that the varying electrical load has reduced, and, in response, operate the fuel cell unit with the operational parameter having a second value such that the fuel cell unit produces an amount of electrical power below the limited maximum amount of electrical power.