In the case of EG, the areal activities produced in the small and large reactors were indistinguishable across 10 consecutive cycles, whereas in the case of PET, the areal activity was consistently higher in the large reactor by 191.7 ± 155.8 µmolH 2 m -2 h -1 for HGM/CNx|Pt and 116.0 ± 50.5 µmolH 2 m -2 h -1 for HGM/CNx|Ni2P. We speculate that the higher average activity in PET may be related to the speed at which the floating composite separates into a ring due to surface tension effects in the small reactors; in the large reactor, no separation patterns were observed, and the floating composite maintained a uniform layer throughout the 2 h irradiation periods. Two clear trends were established from the up-scaled floating composite application: floating PR reactions can be scaled with area without a loss in specific or areal activity, or composite recovery, and that Pt is a stable co-catalyst material suitable for application in multi-use PR composites.