A hydrocarbon generation system that combines a solid oxide electrolysis cell (SOEC) and a Fischer-Tropsch unit in a single microtubular reactor is described. This system can directly synthesize hydrocarbons from carbon dioxide and water. High temperature co-electrolysis of H2O and CO2 and low temperature Fischer-Tropsch (F-T) process are integrated in a single microtubular reactor by designation of a temperature gradient along the axial length of the microtubular reactor. The microtubular reactor can provide direct conversion of CO2 to hydrocarbons for use as feedstock or energy storage.