Contrasting Transient Photocurrent Characteristics for Thin Films of Vacuum-Doped “Grey” TiO2 and “Grey” Nb2O5

Moisés A. Araújo, Murilo F. Gromboni, Frank Marken, Stephen Parker, Laurence Peter, Josh Turner, Helen C. Aspinall, Kate Black, Lucia Mascaro

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Photo-catalytic performance for oxide films, here for inkjet-printed TiO2 (ca. 1 μm thickness on FTO) and for spray-pyrolysis-coated Nb2O5 (ca. 1 μm thickness on FTO), is affected by oxygen vacancies that form during vacuum-heat treatment at 550 °C. The effects of the oxygen vacancies are associated with formation of Ti(III) and Nb(IV) sites, respectively, and therefore optically visible as “grey” coloration. Photo-electrochemical light-on-off transient experiments are performed in the limit of thin film photoanodes, where front and back illumination result in the same photo-current responses (i.e. with negligible effects from internal light absorption gradients). It is shown that generally the magnitude of photo-currents correlates linearly with light intensity, which is indicative of dominant “photo-capacitive” behaviour. At an applied voltage of 0.4 V vs. SCE (in the plateau region of the photo-current responses) the potential and also the pH (going from 1.0 M KOH to 0.1 M HClO4 in the presence of methanol quencher) have no significant effect on photo-currents; that is, surface chemical/kinetic effects appear to be unimportant and interfacial hole transfer may be rate limiting. Under these conditions (and based on a simplistic mechanistic model) changes in photo-currents introduced by oxygen vacancy doping (detrimental for TiO2 and beneficial for Nb2O5) are assigned primarily to changes in electron mobility.
Original languageEnglish
Number of pages42
JournalApplied Catalysis B: Environmental
Early online date24 May 2018
Publication statusPublished - 2018

Fingerprint

Oxygen vacancies
Photocurrents
Vacuum
Thin films
Spray pyrolysis
Electron mobility
oxygen
Reaction kinetics
Light absorption
Oxide films
Methanol
Lighting
Heat treatment
Doping (additives)
light intensity
pyrolysis
spray
Electric potential
methanol
oxide

Cite this

Contrasting Transient Photocurrent Characteristics for Thin Films of Vacuum-Doped “Grey” TiO2 and “Grey” Nb2O5. / Araújo, Moisés A.; Gromboni, Murilo F.; Marken, Frank; Parker, Stephen; Peter, Laurence; Turner, Josh; Aspinall, Helen C.; Black, Kate; Mascaro, Lucia.

In: Applied Catalysis B: Environmental, 2018.

Research output: Contribution to journalArticle

@article{0ef2c0e89deb4aa28b7f30a4afd3fba4,
title = "Contrasting Transient Photocurrent Characteristics for Thin Films of Vacuum-Doped “Grey” TiO2 and “Grey” Nb2O5",
abstract = "Photo-catalytic performance for oxide films, here for inkjet-printed TiO2 (ca. 1 μm thickness on FTO) and for spray-pyrolysis-coated Nb2O5 (ca. 1 μm thickness on FTO), is affected by oxygen vacancies that form during vacuum-heat treatment at 550 °C. The effects of the oxygen vacancies are associated with formation of Ti(III) and Nb(IV) sites, respectively, and therefore optically visible as “grey” coloration. Photo-electrochemical light-on-off transient experiments are performed in the limit of thin film photoanodes, where front and back illumination result in the same photo-current responses (i.e. with negligible effects from internal light absorption gradients). It is shown that generally the magnitude of photo-currents correlates linearly with light intensity, which is indicative of dominant “photo-capacitive” behaviour. At an applied voltage of 0.4 V vs. SCE (in the plateau region of the photo-current responses) the potential and also the pH (going from 1.0 M KOH to 0.1 M HClO4 in the presence of methanol quencher) have no significant effect on photo-currents; that is, surface chemical/kinetic effects appear to be unimportant and interfacial hole transfer may be rate limiting. Under these conditions (and based on a simplistic mechanistic model) changes in photo-currents introduced by oxygen vacancy doping (detrimental for TiO2 and beneficial for Nb2O5) are assigned primarily to changes in electron mobility.",
author = "Ara{\'u}jo, {Mois{\'e}s A.} and Gromboni, {Murilo F.} and Frank Marken and Stephen Parker and Laurence Peter and Josh Turner and Aspinall, {Helen C.} and Kate Black and Lucia Mascaro",
year = "2018",
language = "English",
journal = "Applied Catalysis B: Environmental",
issn = "0926-3373",
publisher = "Elsevier",

}

TY - JOUR

T1 - Contrasting Transient Photocurrent Characteristics for Thin Films of Vacuum-Doped “Grey” TiO2 and “Grey” Nb2O5

AU - Araújo, Moisés A.

AU - Gromboni, Murilo F.

AU - Marken, Frank

AU - Parker, Stephen

AU - Peter, Laurence

AU - Turner, Josh

AU - Aspinall, Helen C.

AU - Black, Kate

AU - Mascaro, Lucia

PY - 2018

Y1 - 2018

N2 - Photo-catalytic performance for oxide films, here for inkjet-printed TiO2 (ca. 1 μm thickness on FTO) and for spray-pyrolysis-coated Nb2O5 (ca. 1 μm thickness on FTO), is affected by oxygen vacancies that form during vacuum-heat treatment at 550 °C. The effects of the oxygen vacancies are associated with formation of Ti(III) and Nb(IV) sites, respectively, and therefore optically visible as “grey” coloration. Photo-electrochemical light-on-off transient experiments are performed in the limit of thin film photoanodes, where front and back illumination result in the same photo-current responses (i.e. with negligible effects from internal light absorption gradients). It is shown that generally the magnitude of photo-currents correlates linearly with light intensity, which is indicative of dominant “photo-capacitive” behaviour. At an applied voltage of 0.4 V vs. SCE (in the plateau region of the photo-current responses) the potential and also the pH (going from 1.0 M KOH to 0.1 M HClO4 in the presence of methanol quencher) have no significant effect on photo-currents; that is, surface chemical/kinetic effects appear to be unimportant and interfacial hole transfer may be rate limiting. Under these conditions (and based on a simplistic mechanistic model) changes in photo-currents introduced by oxygen vacancy doping (detrimental for TiO2 and beneficial for Nb2O5) are assigned primarily to changes in electron mobility.

AB - Photo-catalytic performance for oxide films, here for inkjet-printed TiO2 (ca. 1 μm thickness on FTO) and for spray-pyrolysis-coated Nb2O5 (ca. 1 μm thickness on FTO), is affected by oxygen vacancies that form during vacuum-heat treatment at 550 °C. The effects of the oxygen vacancies are associated with formation of Ti(III) and Nb(IV) sites, respectively, and therefore optically visible as “grey” coloration. Photo-electrochemical light-on-off transient experiments are performed in the limit of thin film photoanodes, where front and back illumination result in the same photo-current responses (i.e. with negligible effects from internal light absorption gradients). It is shown that generally the magnitude of photo-currents correlates linearly with light intensity, which is indicative of dominant “photo-capacitive” behaviour. At an applied voltage of 0.4 V vs. SCE (in the plateau region of the photo-current responses) the potential and also the pH (going from 1.0 M KOH to 0.1 M HClO4 in the presence of methanol quencher) have no significant effect on photo-currents; that is, surface chemical/kinetic effects appear to be unimportant and interfacial hole transfer may be rate limiting. Under these conditions (and based on a simplistic mechanistic model) changes in photo-currents introduced by oxygen vacancy doping (detrimental for TiO2 and beneficial for Nb2O5) are assigned primarily to changes in electron mobility.

M3 - Article

JO - Applied Catalysis B: Environmental

JF - Applied Catalysis B: Environmental

SN - 0926-3373

ER -