Disclosed are an apparatus and method used to preheat a working fluid for a subsequent solar-driven dissociation reaction. The working fluid is first passed through a blackbody receiver where it absorbs thermal energy, and is subsequently exposed to direct solar radiation. The present invention allows the working fluid to absorb relatively large amounts of solar energy a elevated temperatures, while the blackbody absorber remains at a relatively low temperature, thus minimizing energy losses through reradiation and enhancing the efficiency of the overall energy exchange.