Liquid phase processes for producing fuel in a reactor comprising the step of combining at least one oxidizable reactant with liquid water and at least one electrolyte to form a mixture and conducting a fuel-producing reaction in the presence of an electron transfer material, wherein the mixture permits the movement or transport of ions and electrons to facilitate the efficient production of the fuel. An alternative embodiment produces fuel in an electrochemical cell, the reaction characterized by an overall thermodynamic energy balance according to the half-cell reactions occurring at the anode and cathode. Energy generated and/or required by the system components is directed according to the thermodynamic requirements of the half-cell reactions, thereby realizing improved fuel production efficiency.