title: Nanoporous TiO2 and WO3 films by anodization of titanium and tungsten substrates: influence of process variables on morphology and photoelectrochemical response.
abstract: The photoelectrochemical response of nanoporous films, obtained by anodization of Ti and W substrates in a variety of corrosive media and at preselected voltages in the range from 10 to 60 V, was studied. The as-deposited films were subjected to thermal anneal and characterized by scanning electron microscopy and X-ray diffraction. Along with the anodization media developed by previous authors, the effect of poly(ethylene glycol) (PEG 400) or D-mannitol as a modifier to the NH4F electrolyte and glycerol addition to the oxalic acid electrolyte was studied for TiO2 and WO3, respectively. In general, intermediate anodization voltages and film growth times yielded excellent-quality photoelectrochemical response for both TiO2 and WO3 as assessed by linear-sweep photovoltammetry and photoaction spectra. The photooxidation of water and formate species was used as reaction probes to assess the photoresponse quality of the nanoporous oxide semiconductor films. In the presence of formate as an electron donor, the incident photon to electron conversion efficiency (IPCE) ranged from approximately 130% to approximately 200% for both TiO2 and WO3 depending on the film preparation protocol. The best photoactive films were obtained from poly(ethylene glycol) (PEG 400) containing NH4F for TiO2 and from aqueous NaF for WO3.
authors.affiliation: Center for Renewable Energy Science and Technology, The University of Texas at Arlington, Arlington, Texas 76019-0065, USA. ntacconi@uta.edu
authors.forename: N R
authors.initials: NR
authors.lastname: de Tacconi
authors.forename: C R
authors.initials: CR
authors.lastname: Chenthamarakshan
authors.forename: G
authors.initials: G
authors.lastname: Yogeeswaran
authors.forename: A
authors.initials: A
authors.lastname: Watcharenwong
authors.forename: R S
authors.initials: RS
authors.lastname: de Zoysa
authors.forename: N A
authors.initials: NA
authors.lastname: Basit
authors.forename: K
authors.initials: K
authors.lastname: Rajeshwar
mesh_terms: D064751:Ammonium Compounds; D004563:Electrochemistry; D004573:Electrolytes; D005459:Fluorides / Q000737:chemistry; D005990:Glycerol / Q000737:chemistry; D008353:Mannitol / Q000737:chemistry; D008567:Membranes, Artificial; D008855:Microscopy, Electron, Scanning; D049329:Nanostructures / Q000737:chemistry*; D019815:Oxalic Acid / Q000737:chemistry; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size; D010777:Photochemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D016062:Porosity; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012680:Sensitivity and Specificity; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014414:Tungsten / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D064751:Ammonium Compounds; D004573:Electrolytes; D008567:Membranes, Artificial; D010087:Oxides; D000644:Quaternary Ammonium Compounds; C009495:titanium dioxide; D008353:Mannitol; D011092:Polyethylene Glycols; C024822:ammonium fluoride; C511604:tungsten oxide; D019815:Oxalic Acid; D014025:Titanium; D005990:Glycerol; D005459:Fluorides; D014414:Tungsten