Disclosed are apparatuses, systems, methods, and devices for generating hydrogen pyrolysis of hydrocarbons (methane, diesel, JP8, etc.) in a reactor. The reactor includes multiple channels in parallel. A hydrocarbon flows in a channel and decomposes into hydrogen and carbon. Hydrogen gas flows out and some of the carbon will deposit on the channel wall. Once carbon deposition reaches a predetermined level, the hydrocarbon flow stops, and air or oxygen is caused to flow into the channels to oxidize carbon into carbon monoxide or carbon dioxide and supply heat to neighboring channels. Simultaneously, the hydrocarbon will flow into neighboring channels causing decomposition into hydrogen and carbon in the neighboring channels. When the carbon coating in the neighboring channels reaches a predetermined level, the gas flow is switched again to air or oxygen. In this way, each channel alternates between decomposing the hydrocarbon and oxidizing the deposited carbon.