A tipping point for solar production of hydrogen?

Continuous-flow reactor with superior production rate and stability for CO2 reduction using semiconductor photocatalysts

“…Applying flows is particularly effective in photoreactions of photocatalysts where simultaneous oxidation and reduction reactions occur on the surface, as it prevents backward reactions and leads to high reactivity. 18,19 In addition, CO selectivity increases dramatically in the flow reactor. Since the retention time of the adsorbed CO 2 is relatively short in the flow system, 20 it is difficult to proceed with further reaction steps for the production of other chemicals such as CH 4 after its reduction to the simplest form of CO. 21…”

Revealing the Role of Redox Reaction Selectivity and Mass Transfer in Current–Voltage Predictions for Ensembles of Photocatalysts

“…For instance, in the recently reported photocatalytic co-production of H2 and O2 with an impressively large 9% solar-to-hydrogen efficiency, 85 periodic degassing/vacuuming was performed during stability tests over many cycles to prevent recombination of the H2 and O2 formed. 86 Additionally, an optimal temperature of ~70 C was experimentally determined to balance the benefits of improved kinetics of the desired O2 evolution reaction with the losses from the acceleration of the recombination reactions. While flow systems are widely used in electrolyzers, fuel cells, and photoelectrochemical systems, they are much less common in photocatalysis for H2 production.…”