The recyclability of the HGM/CNx composites was assessed in the same small reactors (SA = 4.9 cm 2 , V = 46 mL) under vertical illumination (AM1.5G) using three different substrates: ethylene glycol (EG), polyethylene terephthalate (PET), and cellulose. The EG and PET solutions were prepared in 1 mol L -1 KOH, reflecting the pre-treatment conditions for solid PET, while the cellulose was prepared by enzymatic pre-treatment and had a pH 5 solution containing 50 mmol L -1 sodium acetate. The same HGM/CNx composite (1:3 HGM:melamine) was applied in 10 consecutive 2 h PR trials and each set of 10 runs was performed in triplicate using different HGM/CNx samples. The floating HGM/CNx mass recovery after 10 trials averaged to (58.9 ± 6.4)% in the small reactors with no significant difference in recovery between the HGM/CNx|Pt (61.4 ± 3.7%) and HGM/CNx|Ni2P (56.5 ± 8.3%) samples (Table , ESI).