Mn3O4 (M) incorporated graphenes (G) synthesized by a deposition–solvothermal process, formed at
various nominal weight percentages (G1M1, G3M1 and G1M3), were efficiently used for the
photodegradation of methylene blue dye (MB) under visible light illumination (l > 420 nm, 88 W,
20 ppm, 298 K) and under microwave irradiation (800 W, 2.45 GHz, 373 K). These materials were
characterized using XRD, TEM-SAED, UV-Vis diffuse reflectance, N2 sorptiometry, FTIR and Raman
techniques. Amongst the nanocomposites, G3M1 of polyhedral structure and an average domain equal
to 10–12 nm has presented unique photo-degradation performance (100% degradation, 60 min, 0.0791
min
1 and TOC of 60%) exceeding the rest of the materials. This was mainly due to the extraordinary
optical properties and to the strong interaction between Mn3O4 and graphene through which charge
recombination is hampered. Based on the conduction and valence band edges together with the studied
reactive species, it has been shown that cOH was the dominant species responsible for the MB
degradation. Interestingly, the G3M1 nanocomposite has shown fascinating microwave absorption
properties and is capable of degrading MB at a faster rate (0.287 min
1) than the one conducted via
photocatalysis. Scavenger studies have shown that cOH and electrons were responsible for the excellent
performance of the MB microwave degradation. The microwave results were discussed in view of the
marked increase in dielectric constant (3

) and dielectric loss (3
00) in the studied frequency range of
1.0 Hz to 100 kHz, in addition to the electronic conductivity measurements. This work offers an
exceptional approach for exploring high-performance microwave absorption as well as distinctive visible