Strong interfacial charge transfer between hausmannite manganese oxide and alumina for efficient photocatalysis

Well crystalline manganese oxide(Mn_(3)O_(4))nanoparticles anchored on gamma alumina(γ-Al_(2)O_(3))have been successfully tailored via a proficient and cost effective chemical process as an efficient material for photo catalysis.XRD indicated the composite formation ofγ-Al_(2)O_(3) and hausmannite structure of Mn_(3)O_(4).SEM and TEM revealed that hetero structure of Mn_(3)O_(4)/γ-Al_(2)O_(3) exhibits an amalgam of aggregated nanoparticles and nanorods.XPS demonstrated the chemical states of binary nanocomposite.The band gap tuning has been performed withγ-Al_(2)O_(3) nanoparticles by assimilating hausmannite Mn_(3)O_(4) particles into flower like microstructure of Al_(2)O_(3).The photoluminescence spectra affirmed the enhancement in charge separation in Mn_(3)O_(4)/γ-Al_(2)O_(3) binary hybrid photocatalyst.The band gap becomes narrow with the increase in concentrations of Mn_(3)O_(4).The narrowing of band gap is concorded with crystalline domains of primary aggregated particles.To elucidate the mechanism of the photocatalytic activity linear sweep voltammetry was performed.The results showed that Mn_(3)O_(4)/γ-Al_(2)O_(3) nanocomposite revealed the enhancement in current density as compared to pureγ-Al_(2)O_(3) which confirmed the electron transfer from Mn_(3)O_(4) toγ-Al_(2)O_(3) through the interfacial potential gradient in conduction bands.The optimum concentration of 6.0%Mn_(3)O_(4)/γ-Al_(2)O_(3) for hybrid structure showed an excellent photocatalytic activity under visible light due to narrow band gap energy.High degree distribution of Mn_(3)O_(4) nano architects overlying onγ-Al_(2)O_(3) induces a significant synergic effect betweenγ-Al_(2)O_(3) and hausmannite phase of manganese oxide(Mn_(3)O_(4)).This strong interfacial contact betweenγ-Al_(2)O_(3) and Mn_(3)O_(4) endures the quick transfer of photo generated charge carriers across interface.

Competitive role of nitrogen functionalities of N doped GO and sensitizing effect of Bi_(2)O_(3)QDs on TiO_(2)for water remediation

The promising solar irradiated photocatalyst by pairing of bismuth oxide quantum dots(BQDs)doped TiO_(2)with nitrogen doped graphene oxide(NGO)nanocomposite(NGO/BQDs-TiO_(2))was fabricated.It was used for degradation of organic pollutants like 2,4-dichlorophenol(2,4-DCP)and stable dyes,i.e.Rhodamine B and Congo Red.X-ray diffraction(XRD)profile of NGO showed reduction in oxygenic functional groups and restoring of graphitic crystal structure.The characteristic diffraction peaks of TiO_(2)and its composites showed crystalline anatase TiO_(2).Morphological images represent spherical shaped TiO_(2)evenly covered with BQDs spread on NGO sheet.The surface linkages of NO-O-Ti,C-O-Ti,Bi-O-Ti and vibrational modes are observed by Fourier transform infrared spectroscopy(FTIR)and Raman studies.BQDs and NGO modified TiO_(2)results into red shifting in visible region as studied in diffused reflectance spectroscopy(DRS).NGO and BQDs in TiO_(2)are linked with defect centers which reduced the recombination of free charge carriers by quenching of photoluminescence(PL)intensities.X-ray photoelectron spectroscopy(XPS)shows that no peak related to C-O in NGO/BQDs-TiO_(2)is observed.This indicated that doping of nitrogen into GO has reduced some oxygen functional groups.Nitrogen functionalities in NGO and photosensitizing effect of BQDs in ternary composite have improved photocatalytic activity against organic pollutants.Intermediate byproducts during photo degradation process of 2,4-DCP were studied through high performance liquid chromatography(HPLC).Study of radical scavengers indicated that O_(2)^(·-) has significant role for degradation of 2,4-DCP.Our investigations propose that fabricated nanohybrid architecture has potential for degradation of environmental pollutions.