Upcycling of wastewater via effective photocatalytic hydrogen production using MnO₂ nanoparticles—decorated activated carbon nanoflakes

In the present work, we demonstrated the upcycling technique of effective wastewater treatment via photocatalytic hydrogen production by using the nanocomposites of manganese oxide-decorated activated carbon (MnO₂-AC). The nanocomposites were sonochemically synthesized in pure water by utilizing MnO₂ nanoparticles and AC nanoflakes that had been prepared through green routes using the extracts of Brassica oleracea and Azadirachta indica, respectively. MnO₂-AC nanocomposites were confirmed to exist in the form of nanopebbles with a high specific surface area of ~109 m² /g. When using the MnO₂-AC nanocomposites as a photocatalyst for the wastewater treatment, they exhibited highly efficient hydrogen production activity. Namely, the high hydrogen production rate (395 mL/h) was achieved when splitting the synthetic sulphide effluent (S²⁻ = 0.2 M) via the photocatalytic reaction by using MnO₂-AC. The results stand for the excellent energy-conversion capability of the MnO₂-AC nanocomposites, particularly, for photocatalytic splitting of hydrogen from sulphide wastewater.