An electrolytic cell includes a liquid metal cathode, an anode, and a molten salt electrolyte in contact with the liquid metal cathode and the anode. The molten salt electrolyte includes carbonate ions, and the electrolytic cell is configured to reduce the carbonate ions at the surface of the cathode or in the vicinity of the cathode to yield a carbon material and oxide ions. Producing a carbon material in the electrolytic cell includes providing carbonate ions to the electrolytic cell, reducing the carbonate ions at the liquid metal cathode to yield the carbon material, and removing the carbon material from the electrolytic cell.

An electrolytic cell includes a liquid metal cathode, an anode, and a molten salt electrolyte in contact with the liquid metal cathode and the anode. The molten salt electrolyte includes carbonate ions, and the electrolytic cell is configured to reduce the carbonate ions at the surface of the cathode or in the vicinity of the cathode to yield a carbon material and oxide ions. Producing a carbon material in the electrolytic cell includes providing carbonate ions to the electrolytic cell, reducing the carbonate ions at the liquid metal cathode to yield the carbon material, and removing the carbon material from the electrolytic cell.

A hydrogen system includes: a compressor that includes an anode, a cathode, and an electrolyte membrane interposed therebetween and generates compressed hydrogen by applying a voltage between the anode and the cathode to move protons extracted from anode fluid supplied to the anode to the cathode; a voltage applicator that applies the voltage between the anode and the cathode; a first flow passage through which a cathode off-gas containing the compressed hydrogen discharged from the cathode is supplied to the anode of the compressor; a first on-off valve disposed in the first flow passage; and a controller that causes the voltage applicator to apply the voltage with the first on-off valve opened during a period of time from startup of the hydrogen system until supply of the cathode off-gas to a hydrogen reservoir is started.

A hydrogen system includes: a compressor that includes an anode, a cathode, and an electrolyte membrane interposed therebetween and generates compressed hydrogen by applying a voltage between the anode and the cathode to move protons extracted from anode fluid supplied to the anode to the cathode; a voltage applicator that applies the voltage between the anode and the cathode; a first flow passage through which a cathode off-gas containing the compressed hydrogen discharged from the cathode is supplied to the anode of the compressor; a first on-off valve disposed in the first flow passage; and a controller that causes the voltage applicator to apply the voltage with the first on-off valve opened during a period of time from startup of the hydrogen system until supply of the cathode off-gas to a hydrogen reservoir is started.

Herein discussed is an electrochemical reactor comprising a first electrode, wherein the first electrode is liquid when the reactor is in operation; a second electrode having a metallic phase and a ceramic phase, wherein the metallic phase is electronically conductive and wherein the ceramic phase is ionically conductive; and a membrane, wherein the membrane is positioned between the first and second electrodes and is in contact with the first and second electrodes, wherein the membrane is mixed conducting. Also discussed herein is a method of producing hydrogen or carbon monoxide comprising: (a) providing an electrochemical reactor having an anode, a cathode, and a membrane between the anode and the cathode, wherein the anode is liquid when the reactor is in operation and wherein the membrane is mixed conducting; (b) introducing a feedstock to the anode; (c) introducing a stream to the cathode, wherein the stream comprises water or carbon dioxide.

Herein discussed is an electrochemical reactor comprising a first electrode, wherein the first electrode is liquid when the reactor is in operation; a second electrode having a metallic phase and a ceramic phase, wherein the metallic phase is electronically conductive and wherein the ceramic phase is ionically conductive; and a membrane, wherein the membrane is positioned between the first and second electrodes and is in contact with the first and second electrodes, wherein the membrane is mixed conducting. Also discussed herein is a method of producing hydrogen or carbon monoxide comprising: (a) providing an electrochemical reactor having an anode, a cathode, and a membrane between the anode and the cathode, wherein the anode is liquid when the reactor is in operation and wherein the membrane is mixed conducting; (b) introducing a feedstock to the anode; (c) introducing a stream to the cathode, wherein the stream comprises water or carbon dioxide.

Two phased production of hydrogen involving an electrolytic cell containing first and second electrodes and a solution comprising a metal salt. The first and second electrodes are connected to an external electric energy source during a charging phase, which deposits the metal of the metal salt on the first electrode and evolves oxygen on the second electrode. Once the charging phase has been completed the first and second electrodes are disconnected from the external electric energy source with the cell containing the deposited metal kept in a standby condition until hydrogen production is required. During a discharging phase, the first and second electrodes are short circuited, whereby the metal is dissolved from the first electrode and hydrogen is evolved from the second electrode without any appreciable simultaneous withdrawal of electrical energy. The production of hydrogen is thereby increased accordingly. Variations of the above are also provided.

Two phased production of hydrogen involving an electrolytic cell containing first and second electrodes and a solution comprising a metal salt. The first and second electrodes are connected to an external electric energy source during a charging phase, which deposits the metal of the metal salt on the first electrode and evolves oxygen on the second electrode. Once the charging phase has been completed the first and second electrodes are disconnected from the external electric energy source with the cell containing the deposited metal kept in a standby condition until hydrogen production is required. During a discharging phase, the first and second electrodes are short circuited, whereby the metal is dissolved from the first electrode and hydrogen is evolved from the second electrode without any appreciable simultaneous withdrawal of electrical energy. The production of hydrogen is thereby increased accordingly. Variations of the above are also provided.

A synthesis gas production system for producing CO and H.sub.2 by electrolyzing an aqueous solution containing CO.sub.2 includes: an electrolysis device including an anode chamber and a cathode chamber separated by a separator membrane; a cathode-side circulation line connected to the cathode chamber to circulate a cathode solution containing CO.sub.2; a catalyst supply device provided in the cathode-side circulation line to supply a CO production catalyst to the cathode solution; and a gas composition detection device configured to measure a ratio between CO and H.sub.2 in a production gas produced in the cathode chamber. At least one of control of a supply amount of the CO production catalyst by the catalyst supply device and control of a voltage applied between the anode and the cathode by the electrolysis device is performed to make a ratio of H.sub.2 to CO in the production gas be within a predetermined target range.

A synthesis gas production system for producing CO and H.sub.2 by electrolyzing an aqueous solution containing CO.sub.2 includes: an electrolysis device including an anode chamber and a cathode chamber separated by a separator membrane; a cathode-side circulation line connected to the cathode chamber to circulate a cathode solution containing CO.sub.2; a catalyst supply device provided in the cathode-side circulation line to supply a CO production catalyst to the cathode solution; and a gas composition detection device configured to measure a ratio between CO and H.sub.2 in a production gas produced in the cathode chamber. At least one of control of a supply amount of the CO production catalyst by the catalyst supply device and control of a voltage applied between the anode and the cathode by the electrolysis device is performed to make a ratio of H.sub.2 to CO in the production gas be within a predetermined target range.