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Rudatis P, Hrubesch J, Kremshuber S, Apaydin DH, Eder D. Enhanced Oxygen Evolution Reaction Activity in Hematite Photoanodes: Effect of Sb-Li Co-Doping. ACS OMEGA 2023; 8:2027-2033. [PMID: 36687027 PMCID: PMC9850461 DOI: 10.1021/acsomega.2c05241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 12/01/2022] [Indexed: 06/17/2023]
Abstract
Co-doping represents a valid approach to maximize the performance of photocatalytic and photoelectrocatalytic semiconductors. Albeit theoretical predictions in hematite suggesting a bulk n-type doping and a surface p-type doping would deliver best results, hematite co-doping with coupled cations possessing low and high oxidation states has shown promising results. Herein, we report, for the first time, Sb and Li co-doping of hematite photoanodes. Particularly, this is also a seminal work for the introduction of the highly reactive Sb5+ directly into the hematite thin films. Upon co-doping, we have a synergistic effect on the current densities with a 67-fold improvement over the standard. Via a combined investigation with profuse photoelectrochemical measurements, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman analyses, we confirm the two doping roles of Sb5+ and Li+ as the substitutional and interstitial dopant, respectively. The improvements are attributed to a higher charge carrier concentration along with a lower charge transfer resistance at the surface.
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Berardi S, Kopula Kesavan J, Amidani L, Meloni EM, Marelli M, Boscherini F, Caramori S, Pasquini L. Better Together: Ilmenite/Hematite Junctions for Photoelectrochemical Water Oxidation. ACS APPLIED MATERIALS & INTERFACES 2020; 12:47435-47446. [PMID: 32986954 PMCID: PMC8014905 DOI: 10.1021/acsami.0c12275] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 09/28/2020] [Indexed: 06/11/2023]
Abstract
Hematite (α-Fe2O3) is an earth-abundant indirect n-type semiconductor displaying a band gap of about 2.2 eV, useful for collecting a large fraction of visible photons, with frontier energy levels suitably aligned for carrying out the photoelectrochemical water oxidation reaction under basic conditions. The modification of hematite mesoporous thin-film photoanodes with Ti(IV), as well as their functionalization with an oxygen-evolving catalyst, leads to a 6-fold increase in photocurrent density with respect to the unmodified electrode. In order to provide a detailed understanding of this behavior, we report a study of Ti-containing phases within the mesoporous film structure. Using X-ray absorption fine structure and high-resolution transmission electron microscopy coupled with electron energy loss spectroscopy, we find that Ti(IV) ions are incorporated within ilmenite (FeTiO3) near-surface layers, thus modifying the semiconductor-electrolyte interface. To the best of our knowledge, this is the first time that an FeTiO3/α-Fe2O3 composite is used in a photoelectrochemical setup for water oxidation. In fact, previous studies of Ti(IV)-modified hematite photoanodes reported the formation of pseudobrookite (Fe2TiO5) at the surface. By means of transient absorption spectroscopy, transient photocurrent experiments, and electrochemical impedance spectroscopy, we show that the formation of the Fe2O3/FeTiO3 interface passivates deep traps at the surface and induces a large density of donor levels, resulting in a strong depletion field that separates electron and holes, favoring hole injection in the electrolyte. Our results provide the identification of a phase coexistence with enhanced photoelectrochemical performance, allowing for the rational design of new photoanodes with improved kinetics.
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Affiliation(s)
- Serena Berardi
- Department
of Chemical and Pharmaceutical Sciences, University of Ferrara, via Luigi Borsari 46, 44121 Ferrara, Italy
| | - Jagadesh Kopula Kesavan
- Department
of Physics and Astronomy, Alma Mater Studiorum−Università
di Bologna, viale Carlo Berti Pichat 6/2, 40127 Bologna, Italy
| | - Lucia Amidani
- Helmholtz-Zentrum
Dresden-Rossendorf, c/o European Synchrotron
Radiation Facility, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Elia Marek Meloni
- Department
of Chemical and Pharmaceutical Sciences, University of Ferrara, via Luigi Borsari 46, 44121 Ferrara, Italy
| | - Marcello Marelli
- CNR-SCITEC, Istituto di Scienze e Tecnologie Chimiche “Giulio
Natta”, Via Gaudenzio Fantoli 16/15, 20138 Milano, Italy
| | - Federico Boscherini
- Department
of Physics and Astronomy, Alma Mater Studiorum−Università
di Bologna, viale Carlo Berti Pichat 6/2, 40127 Bologna, Italy
| | - Stefano Caramori
- Department
of Chemical and Pharmaceutical Sciences, University of Ferrara, via Luigi Borsari 46, 44121 Ferrara, Italy
| | - Luca Pasquini
- Department
of Physics and Astronomy, Alma Mater Studiorum−Università
di Bologna, viale Carlo Berti Pichat 6/2, 40127 Bologna, Italy
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Seriani N. Ab initio simulations of water splitting on hematite. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:463002. [PMID: 29057752 DOI: 10.1088/1361-648x/aa84d9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In recent years, hematite has attracted great interest as a photocatalyst for water splitting, but many questions remain unanswered about the mechanisms and the main limiting factors. For this reason, density functional theory has been used to understand the optical, electronic and chemical properties of this material at an atomistic level. Bulk doping can be used to reduce the band gap, and to increase photoabsorption and charge mobility. Charge transport takes place through adiabatic polaron hopping. The stable (0 0 0 1) surface has a stoichiometric termination when exposed to oxygen, it becomes hydroxylated in water, and it has an oxygen-rich termination under illumination in a photoelectrochemical setup. On the oxygen-rich termination, surface states are present that might act as recombination centres for electrons and holes. On the contrary, on the hydroxylated termination surface states appear only on reaction intermediates. The intrinsic surface states disappear in the presence of an overlayer of gallium oxide. The reaction of water oxidation is assumed to proceed by four proton-coupled electron transfers and it is shown to involve a nucleophilic attack with the formation of an OOH group. Calculated overpotentials are in the range of 0.5-0.6 V. Open questions and future research directions are briefly discussed.
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Affiliation(s)
- Nicola Seriani
- The Abdus Salam ICTP, Strada Costiera 11, 34151 Trieste, Italy
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Orlandi M, Mazzi A, Arban G, Bazzanella N, Rudatis P, Caramori S, Patel N, Fernandes R, Bignozzi CA, Miotello A. On the effect of Sn-doping in hematite anodes for oxygen evolution. Electrochim Acta 2016. [DOI: 10.1016/j.electacta.2016.08.046] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Orlandi M, Dalle Carbonare N, Caramori S, Bignozzi CA, Berardi S, Mazzi A, El Koura Z, Bazzanella N, Patel N, Miotello A. Porous versus Compact Nanosized Fe(III)-Based Water Oxidation Catalyst for Photoanodes Functionalization. ACS APPLIED MATERIALS & INTERFACES 2016; 8:20003-20011. [PMID: 27447454 DOI: 10.1021/acsami.6b05135] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Integrated absorber/electrocatalyst schemes are increasingly adopted in the design of photoelectrodes for photoelectrochemical cells because they can take advantage of separately optimized components. Such schemes also lead to the emergence of novel challenges, among which parasitic light absorption and the nature of the absorber/catalyst junction features prominently. By taking advantage of the versatility of pulsed-laser deposition technique, we fabricated a porous iron(III) oxide nanoparticle-assembled coating that is both transparent to visible light and active as an electrocatalyst for water oxidation. Compared to a compact morphology, the porous catalyst used to functionalize crystalline hematite photoanodes exhibits a superior photoresponse, resulting in a drastic lowering of the photocurrent overpotential (about 200 mV) and a concomitant 5-fold increase in photocurrents at 1.23 V versus reversible hydrogen electrode. Photoelectrochemical impedance spectroscopy indicated a large increase in trapped surface hole capacitance coupled with a decreased charge transfer resistance, consistent with the possible formation of an adaptive junction between the absorber and the porous nanostructured catalyst. The observed effect is among the most prominent reported for the coupling of an electrocatalyst with a thin layer absorber.
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Affiliation(s)
- Michele Orlandi
- Department of Physics, University of Trento , I-38123, Povo, Trento, Italy
| | - Nicola Dalle Carbonare
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara , Via Fossato di Mortara 17-19, 44100 Ferrara, Italy
| | - Stefano Caramori
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara , Via Fossato di Mortara 17-19, 44100 Ferrara, Italy
| | - Carlo A Bignozzi
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara , Via Fossato di Mortara 17-19, 44100 Ferrara, Italy
| | - Serena Berardi
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara , Via Fossato di Mortara 17-19, 44100 Ferrara, Italy
| | - Alberto Mazzi
- Department of Physics, University of Trento , I-38123, Povo, Trento, Italy
| | - Zakaria El Koura
- Department of Physics, University of Trento , I-38123, Povo, Trento, Italy
| | - Nicola Bazzanella
- Department of Physics, University of Trento , I-38123, Povo, Trento, Italy
| | - Nainesh Patel
- Department of Physics, University of Mumbai , Vidyanagari, Santacruz (E), Mumbai 400 098, India
| | - Antonio Miotello
- Department of Physics, University of Trento , I-38123, Povo, Trento, Italy
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Dalle Carbonare N, Boaretto R, Caramori S, Argazzi R, Dal Colle M, Pasquini L, Bertoncello R, Marelli M, Evangelisti C, Bignozzi CA. Photoelectrochemical Behavior of Electrophoretically Deposited Hematite Thin Films Modified with Ti(IV). Molecules 2016; 21:molecules21070942. [PMID: 27447604 PMCID: PMC6273019 DOI: 10.3390/molecules21070942] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 07/13/2016] [Accepted: 07/15/2016] [Indexed: 01/17/2023] Open
Abstract
Doping hematite with different elements is a common strategy to improve the electrocatalytic activity towards the water oxidation reaction, although the exact effect of these external agents is not yet clearly understood. Using a feasible electrophoretic procedure, we prepared modified hematite films by introducing in the deposition solution Ti(IV) butoxide. Photoelectrochemical performances of all the modified electrodes were superior to the unmodified one, with a 4-fold increase in the photocurrent at 0.65 V vs. SCE in 0.1 M NaOH (pH 13.3) for the 5% Ti-modified electrode, which was the best performing electrode. Subsequent functionalization with an iron-based catalyst led, at the same potential, to a photocurrent of ca. 1.5 mA·cm(-2), one of the highest achieved with materials based on solution processing in the absence of precious elements. AFM, XPS, TEM and XANES analyses revealed the formation of different Ti(IV) oxide phases on the hematite surface, that can reduce surface state recombination and enhance hole injection through local surface field effects, as confirmed by electrochemical impedance analysis.
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Affiliation(s)
- Nicola Dalle Carbonare
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 11-17, 44121 Ferrara, Italy.
| | - Rita Boaretto
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 11-17, 44121 Ferrara, Italy.
| | - Stefano Caramori
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 11-17, 44121 Ferrara, Italy.
| | - Roberto Argazzi
- CNR/ISOF c/o Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 11-17, 44121 Ferrara, Italy.
| | - Maurizio Dal Colle
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 11-17, 44121 Ferrara, Italy.
| | - Luca Pasquini
- Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy.
| | - Renzo Bertoncello
- Department of Chemical Sciences, University of Padua, Via F. Marzolo 1, 35131 Padua, Italy.
| | | | | | - Carlo Alberto Bignozzi
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 11-17, 44121 Ferrara, Italy.
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