Electronic transitions of SWCNTs in comparison to GO on Mn₃O₄/TiO₂nanocomposites for hydrogen energy generation and solar photocatalysis

The conductivity of metal/metal oxide-doped TiO₂nanomaterials is enhanced by the incorporation of carbonaceous materials,e.g.single-walled carbon nanotubes (SWCNTs) and graphene oxide (GO). Here, a comparative study was conducted on SWCNTs/Mn₃O₄-TiO₂and GO/Mn₃O₄-TiO₂composite materials for hydrogen evolution reaction (HER) through water splitting and solar induced photodegradation of methyl orange (MO). The morphology of GO/Mn₃O₄-TiO₂showed a quasi-spherical network of TiO₂with patches of Mn₃O₄nanoparticles dispersed on GO sheets. SWCNTs were adhered on the Mn₃O₄-TiO₂surface. The novel features of carbonaceous materials (GO/SWCNTs), fast electronic transition properties of SWCNTs and π-π interaction of carbon materials in composites extended the absorption edges in the visible region and thereby led to reduction of band gap energy. Mn-Ti-C linkages in ternary composites were confirmed through FTIR and Raman studies. Quenching of PL intensity indicated suppression of electron-hole recombination on the surface of SWCNTs/Mn₃O₄-TiO₂. XPS demonstrated bonding configuration and oxidation states of components of the SWCNTs/Mn₃O₄-TiO₂composite. The SWCNTs/Mn₃O₄-TiO₂nanohybrid structure with tailored properties played a noteworthy role in HER with a low onset potential of ∼320 mV at 10 mA cm⁻², a lowR_ctof ∼43.3 Ω, a small Tafel slope of ∼86 mV dec⁻¹and the highest degradation of MO (∼98%) compared to other catalysts. Our findings suggest that the prepared catalysts are promising candidates for multifunctional purposes.