Visible light-driven hydrogen evolution by using mesoporous carbon nitride-metal ferrite (MFe2O4/mpg-CN; M: Mn, Fe, Co and Ni) nanocomposites as catalysts

Four different earth-abundant ferrite nanoparticles (MFe2O4, M: Mn, Fe, Co, Ni) with spinel structure were synthesized by using the surfactant-assisted high temperature thermal decomposition methods and then assembled on mesoporous graphitic carbon nitride (mpg-CN) to study their comparative catalysis for the photocatalytic hydrogen evolution reaction (HER) in the presence of Eosin-Y (EY) as a visible-light sensitizer. The yielded monodisperse ferrite nanoparticles and the MFe2O4/mpg-CN nanocomposites were characterized by using advanced analytical techniques including TEM, XPS, XRD, ICP-MS, and UV–Vis DRS. All the tested MFe2O4/mpg-CN nanocomposites provided the better catalytic performance than that of pristine mpg-CN in the photocatalytic HER and their photocatalytic HER rates are in the order of NiFe2O4/mpg-CN > CoFe2O4/mpg-CN > MnFe2O4/mpg-CN > Fe3O4/mpg-CN > mpg-CN. Among the tested MFe2O4/mpg-CN nanocomposites, NiFe2O4/mpg-CN nanocomposite provided the highest hydrogen generation of 14.56 mmol g−1, which is 6.75 times greater than that of pristine mpg-CN and, using EY as a visible light sensitizer and triethanolamine (TEOA) as a sacrificial reagent. According to the optical properties and energy band positions of the nanocomposites, a plausible mechanism for the NiFe2O4/mpg-CN catalyzed HER is proposed to give insights on the highest activity of NiFe2O4/mpg-CN nanocomposites among others.