Should the Tubular Photocatalytic Reactors Work Continuously or in an Intermittent Manner Instead?

In the past, almost all the slurry tubular photocatalytic reactors were working in a continuous and circulating mode. Herein, we reported a new working mode with intermittent stop of slurry reaction flow for enhanced hydrogen production using a facilely designed channel photocatalytic reactor. The optimal flow rate and light intensity were also investigated to obtain the highest hydrogen production. We found, for the first time, that there is an optimal residence and exposure time for the photocatalytic reaction fluid working with an intermittent which leads to much higher hydrogen production than that of reactors working in a continuous manner. In such a mode, the circulating pump work can be significantly saved. Various characterizations were carried out to analyze the possible reasons underlying our finding. Specifically, as the stopping time increases, solar photon flux can be used more effectively for hydrogen production, but a too long residence time could lead to agglomeration and sedimentation of the photocatalyst particles. As a result, an appropriate time ratio of start/stop for the reactor is needed. Besides, the higher light intensity is beneficial for hydrogen production, while too large light intensity could be detrimental. Our work can provide an important guidance for the further development of similar devices in solar photocatalysis hydrogen production.