A graphite fluid-wall aerosol flow reactor heated with concentrated sunlight has been developed over the past five years for the solar-thermal decarbonization of methane. The fluid-wall is provided by an inert or compatible gas that prevents contact of reactants and products of reaction with a graphite reaction tube. The reactor provides for a low thermal mass that is compatible with intermittent sunlight and the graphite construction allows rapid heating/cooling rates and ultra-high temperatures. The decarbonization of methane has been demonstrated at over 90% for residence times on the order of 10 milliseconds at a reactor wall temperature near 2000 K. The carbon black resulting from the dissociation of methane is nanosized, amorphous, and ash-free and can be used for industrial rubber production. The hydrogen can be supplied to a pipeline and used for chemical processing or to supply fuel cell vehicles.