Exploring anatase-TiO2 doped dilutely with transition metal ions as nano-catalyst for H2O2 decomposition: Spectroscopic and kinetic studies

Pure and dilutely doped nano anatase-TiO2 with 3 at% Nb, Cr, Fe, Ni, Mn, Co or Cu ions were prepared by sol–gel processing. The doping was found by X-ray diffractometry and laser Raman spectroscopy to reduce the average crystallite size of the titania (8 nm) down to <8–3 nm without formation of separate or mixed oxide phases and without deviation from the anatase structure of the titania. Ion scattering spectroscopy observed surface exposure of the dopant ions, but only Mn, Co or Cu dopant ions were found by X-ray photoelectron spectroscopy to form oxygen-mediated bonds with titanium ions. The likely facilitation of d–d electron exchange interactions via such dopant–O–Ti linkages is suggested to provide the necessary bulk and surface attributes for the observed rendering of the host anatase-TiO2 a visible light absorber (as revealed by UV-visible diffuse reflectance spectroscopy) and an active heterogeneous catalyst for H2O2 decomposition (as revealed by gravimetric gasometry of the decomposition reaction). These two dopant-mediated behaviors were exhibited uniquely by the anatase-TiO2 nanoparticles after doping with Mn, Co or Cu ions.

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► 3 at% doping of anatase-TiO2 was affected with Nb, Cr, Fe, Ni, Mn, Co or Cu ions.
► The anatase structure is maintained but the crystallite size decreases down 8–3 nm.
► Only the Mn, Co or Cu ions form dopant–O–Ti linkages.
► Consequently, anatase-TiO2 is rendered a visible light absorber.
► Consequently, anatase-TiO2 is rendered a H2O2 decomposition heterogeneous catalyst.