NOVELTY - Producing (M1) a hydrocarbon comprises: providing electrical energy to a first fuel cell comprising an anode, cathode and polymer electrolyte membrane; electrocatalytically oxidizing a hydrogen source by a first catalyst disposed on the anode to produce protons; and electrocatalytically reducing a hydrocarbonaceous source by the protons and a second catalyst disposed on the cathode to produce a hydrocarbon fuel composition, where the first and second catalysts are each a solid catalyst, and the anode and cathode are separated by the polymer electrolyte membrane.    USE - The method is useful for producing hydrocarbon (claimed) that is used for hydrocarbon fuel applications such as automotive fuel.    ADVANTAGE - The method provides hydrocarbon fuel composition: as storable energy medium in a cost and space-efficient and combustible form; that is utilized to power the energy needs of fuel cells, and generate electrical and/or thermal energy for other uses; and having maximum amount of stored energy. The hydrogen-producing fuel cell feeds the hydrogen source to the catalytic fuel cell without providing additional catalyst on the anode of the fuel cell for hydrocarbon production, and without storing or otherwise providing a source of a combustible hydrogen source (e.g. hydrogen) in order to operate the fuel cell for hydrocarbon production.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) producing (M2) the hydrocarbon comprising: providing electrical energy to the first fuel cell comprising a first anode, first cathode, and first polymer electrolyte membrane; electrocatalytically oxidizing the hydrogen source by the first catalyst disposed on the first anode to produce protons; electrocatalytically reducing the protons by a second catalyst disposed on the first cathode to produce hydrogen; providing the hydrogen from the first fuel cell to a second fuel cell comprising a second anode, second cathode, and second polymer electrolyte membrane; providing electrical energy to the second fuel cell; electrocatalytically oxidizing the hydrogen by a third catalyst disposed on the second anode to produce protons; and electrocatalytically reducing a hydrocarbonaceous source by the protons and a fourth catalyst disposed on the second cathode to produce the fuel composition comprising 1-8C hydrocarbon, where the first, second, third, and fourth catalysts are each a solid catalyst, the first anode and first cathode are separated by the first polymer electrolyte membrane, and the second anode and second cathode are separated by the second polymer electrolyte membrane;    (2) producing (M3) the hydrocarbon comprising: providing electrical energy to a fuel cell comprising first and second anodes, first and second cathodes, and first and second polymer electrolyte membranes; electrocatalytically oxidizing the hydrogen source by the first catalyst disposed on the first anode to produce primary protons; electrocatalytically reducing the primary protons by the second catalyst disposed on the first cathode to produce hydrogen; controlling a provision of the hydrogen to the third catalyst disposed on the second anode; electrocatalytically oxidizing the hydrogen by the third catalyst to produce secondary protons; and electrocatalytically reducing a hydrocarbonaceous source by the secondary protons and a fourth catalyst disposed on the second cathode to produce a 1-8C hydrocarbon, where fourth catalysts is a solid catalyst, and the first cathode and the second anode are separated by a hydrogen regulator to regulate pressure and flow hydrogen gas;    (3) an energy storage system comprising: the first fuel cell comprising the anode, the cathode, the polymer electrolyte membrane and a catalyst; and the second fuel cell coupled to the first fuel cell, where the first fuel cell is configured to oxidize hydrogen, to reduce a water-soluble carbohydrate, and to store energy from the reduction of the water-soluble carbohydrate in the fuel composition, where the composition is 1-8C alkane and/or 1-8C oxygenate; and    (4) an energy source, comprising: the first fuel cell; shunt connected to the anode and the cathode; and the second fuel, where the shunt is configured in a first state to electrically connect the anode and the cathode to reduce the carbohydrate and in a second state to electrically connect the anode and the cathode across an electrical load to provide energy to the electrical load from oxidation of the fuel composition.