This project’s purpose is to construct a reactor capable of exposing photocatalyst nanoparticles to water vapor and light so hydrogen production can be assessed under mixed thermal and photon stimuli. Vapor phase water splitting is relevant for concentrated-solar applications wherein sunlight is focused onto a reactor. A vapor phase reactor has been designed by using thermodynamic analysis combined with design parameters set by researchers. This project will enable the investigation of temperature dependent photocatalytic activity in multivalent metal oxides (e.g. CeO2). Future work will focus on improving the temperature range of the reactor system and testing other photocatalysts.