Fig. 2. Schematic designs of different conceptual powder suspension (top line) and catalyst sheet reactors (bottom line). The catalyst sheets consist of the immobilized-photocatalyst in analog configuration to the suspension reactor. The color scheme of the cocatalysts indicates the selective photocatalysts for HER (blue), OER (red), mediator reduction (dark and light violet) and mediator oxidation (light and dark yellow). Types 2 and 3 include a membrane, and type 3 includes a wire.