Enhanced Photoelectrochemical Performance Of F-doped SnO₂?FTO? Films Through Doping And Modifying Of Metal Ions

Tin oxide(SnO2)is n-type semiconducting oxide with properties of nontoxic,cheap and stable.Due to its wider band gap(3.6 eV),the pure SnO2 can only absorb ultraviolet light,and show poor photocatalytic activity.FTO is fluorine-doped tin oxide,as a kind of transparent conducting materials,to be widely used as the substrate for liquid crystaldisplay(LCD),photocatalytic materials,electrochromic material and solar cells material.Through doping and modifying of metal ions,one can reduce the width of band gap,increase the electrical conductivity and the absorption for visible light of the FTO films,and improve its photoelectrochemical performance unser visible light.In this work,the cathodic polarized FTO film(C-FTO),iron-doped FTO film(F-FTO)and iron-doped,zinc-modified FTO film(ZF-FTO)were prepared on the substrates of FTO transparent conductor glass.Influence of parameters of the cathodic polarization and modifying zinc on the morphology,structure,and the photoelectrochemical performance is studied.The morphologies,structures,compositions and optical properties of samples were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Raman spectra(Raman),UV-Vis spectroscopy(UV-Vis)and Potoluminescence spectrum(PL),respectively.The photoelectrochemical properties of films were measured in 1.0 mol/L NaOH solution undervisible light and zero bias.The details are listed below:1.C-FTO films were prepared through cathodic polarized in a solution of 0.1 mol/L Na2SO4 at 6 mA/cm2 for 350 s,then annealed at 500 ? for 2 h in air.The results of SEM?XRD?XPS and Raman showed that C-FTO films present porous nanostructure and few phase of orthorhombic Sno2.The C-FTO films exhibit favorable photocurrent performance and stability in photoelectrochemical cell.The sample generated a photocurrent about 1.85×10-2 ?A/cm2.2.F-FTO films were obtained by cathodic polarized in a solution of 0.1 mol/L FeSo4 and 0.1 mol/L(NH4)2SO4(pH 1.5)at 6 mA/cm2 for 350 s,then annealed at 500? for 2 h in air.The results of SEM?XRD?XPS and Raman showed that F-FTO films present porous nanostructure,Fe and more phase of orthorhombic SnO2.The photocurrent density of the F-FTO films is 4.95×10-1 ?A/cm2,which is 25 times higher than that of C-FTO films.3.In order to further improve the photoelectrochemical performance of F-FTO film,ZF-FTO films were obtained by dipped in 0.2 mol/L saturated zinc acetate ethanol solution for 10 min based F-FTO precursors,then annealed at 500 ? for 2 h in air.The results reveal that ZF-FTO films showed the same morphology and structure as F-FTO.But the photocurrent density of the ZF-FTO is 2.43 ?A/cm,which is about 5 times higher than that of F-FTO films.For ZF-FTO films,flatband potential(EFB)negative shift from 0.50 to 0.32 V(vs.RHE),and dopant density(N)calculated to be 3.69×1021 cm-3 is much larger than that of F-FTO films.The photoelectrochemical performance of the FTO films can be greatly improved through doping and modifying of matel ions.