Photoelectrochemical water splitting by defects in nanostructured multinary transition metal oxides
Point defects play a crucial role in the performance of functional materials. The most important extrinsic elements for point defects in titanium-based photocatalysts are oxygen, nitrogen, and hydrogen due to their large chemical affinity and substantial solubility with titanium. Therefore, understa...
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| Veröffentlicht in: | Solar energy materials and solar cells 2019-06, Vol.194, p.184-194 |
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| description | Point defects play a crucial role in the performance of functional materials. The most important extrinsic elements for point defects in titanium-based photocatalysts are oxygen, nitrogen, and hydrogen due to their large chemical affinity and substantial solubility with titanium. Therefore, understanding the nature of such defects will help designing high-performance photocatalysts for various applications. Herein, we make use of alloyed multipodal Ti-Nb-Zr-O nanotubes (MPNTs) annealed under different atmospheres: Air, O2, and H2 for enhanced photoelectrochemical water-splitting. Structural analysis using XRD, Raman spectroscopy, and XPS confirmed the formation of a single mixed oxide Ti-Nb-Zr-O in a strained-anatase crystal structure in both Air and Oxygen atmospheres. However, XPS fitting showed the presence of ZrTiO4 and Ti3+ upon annealing in Hydrogen atmosphere. Valence band XPS analysis confirms the presence of valence band tail states causing band-gap reduction in the hydrogen-annealed samples, with an absorption tail reaching NIR/Vis region. Mott-Schottky analysis showed 4 orders of magnitude increase in the carrier density for the samples annealed in hydrogen atmosphere compared to those annealed in Air or O2, owing to the presence of Ti3+ defects/oxygen vacancies, titanium substitution by niobium, and the valence band tail states. These synergistic effects resulted in almost 25-fold enhancement in the photocurrent compared to the performance of the samples annealed in Oxygen or Air. It is thus concluded that annealing in a reducing atmosphere produces disordered and defective structure. Accordingly, the optical and electronic properties of complex metal oxides exhibiting poor performance can be manipulated to produce promising candidates for enhanced photoelectrochemical water splitting.
[Display omitted]
•Point defects controlled the photocatalytic performance of multinary metal oxides.•Strained single mixed oxide is formed upon annealing in both Air and Oxygen.•Upon annealing Hydrogen atmosphere, ZrTiO4 and Ti3+ are formed.•Four orders of magnitude increase in the carrier density was observed for the samples annealed in hydrogen.•25-fold enhancement in the photocurrent was observed for the samples annealed in hydrogen. |
| doi_str_mv | 10.1016/j.solmat.2019.02.011 |
| format | Article |
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[Display omitted]
•Point defects controlled the photocatalytic performance of multinary metal oxides.•Strained single mixed oxide is formed upon annealing in both Air and Oxygen.•Upon annealing Hydrogen atmosphere, ZrTiO4 and Ti3+ are formed.•Four orders of magnitude increase in the carrier density was observed for the samples annealed in hydrogen.•25-fold enhancement in the photocurrent was observed for the samples annealed in hydrogen.</description><identifier>ISSN: 0927-0248</identifier><identifier>EISSN: 1879-3398</identifier><identifier>DOI: 10.1016/j.solmat.2019.02.011</identifier><language>eng</language><publisher>Amsterdam: Elsevier B.V</publisher><subject>Anatase ; Annealing ; Atmosphere ; Atmospheres ; Carrier density ; Coordination compounds ; Crystal defects ; Crystal structure ; Defects ; Electronic properties ; Hydrogen ; Hydrogen storage ; Metal oxides ; Metals ; Multinary metal oxide ; Multipodal nanotubes ; Nanotechnology ; Nanotubes ; Niobium ; Optical properties ; Organic chemistry ; Oxides ; Oxygen ; Photocatalysis ; Photocatalysts ; Photoelectric effect ; Photoelectric emission ; Point defects ; Raman spectroscopy ; Splitting ; Structural analysis ; Synergistic effect ; Tails ; Titanium ; Transition metal oxides ; Transition metals ; Valence band ; Water splitting ; X ray photoelectron spectroscopy</subject><ispartof>Solar energy materials and solar cells, 2019-06, Vol.194, p.184-194</ispartof><rights>2019 Elsevier B.V.</rights><rights>Copyright Elsevier BV Jun 1, 2019</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c334t-2701093420e3f55b3e868ae48abc1b75bb29b01c633002caa46d7c97712429243</citedby><cites>FETCH-LOGICAL-c334t-2701093420e3f55b3e868ae48abc1b75bb29b01c633002caa46d7c97712429243</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktohtml>$$Uhttps://dx.doi.org/10.1016/j.solmat.2019.02.011$$EHTML$$P50$$Gelsevier$$H</linktohtml><link.rule.ids>315,781,785,3551,27929,27930,46000</link.rule.ids></links><search><creatorcontrib>Fawzy, Samar M.</creatorcontrib><creatorcontrib>Omar, Mostafa M.</creatorcontrib><creatorcontrib>Allam, Nageh K.</creatorcontrib><title>Photoelectrochemical water splitting by defects in nanostructured multinary transition metal oxides</title><title>Solar energy materials and solar cells</title><description>Point defects play a crucial role in the performance of functional materials. The most important extrinsic elements for point defects in titanium-based photocatalysts are oxygen, nitrogen, and hydrogen due to their large chemical affinity and substantial solubility with titanium. Therefore, understanding the nature of such defects will help designing high-performance photocatalysts for various applications. Herein, we make use of alloyed multipodal Ti-Nb-Zr-O nanotubes (MPNTs) annealed under different atmospheres: Air, O2, and H2 for enhanced photoelectrochemical water-splitting. Structural analysis using XRD, Raman spectroscopy, and XPS confirmed the formation of a single mixed oxide Ti-Nb-Zr-O in a strained-anatase crystal structure in both Air and Oxygen atmospheres. However, XPS fitting showed the presence of ZrTiO4 and Ti3+ upon annealing in Hydrogen atmosphere. Valence band XPS analysis confirms the presence of valence band tail states causing band-gap reduction in the hydrogen-annealed samples, with an absorption tail reaching NIR/Vis region. Mott-Schottky analysis showed 4 orders of magnitude increase in the carrier density for the samples annealed in hydrogen atmosphere compared to those annealed in Air or O2, owing to the presence of Ti3+ defects/oxygen vacancies, titanium substitution by niobium, and the valence band tail states. These synergistic effects resulted in almost 25-fold enhancement in the photocurrent compared to the performance of the samples annealed in Oxygen or Air. It is thus concluded that annealing in a reducing atmosphere produces disordered and defective structure. Accordingly, the optical and electronic properties of complex metal oxides exhibiting poor performance can be manipulated to produce promising candidates for enhanced photoelectrochemical water splitting.
[Display omitted]
•Point defects controlled the photocatalytic performance of multinary metal oxides.•Strained single mixed oxide is formed upon annealing in both Air and Oxygen.•Upon annealing Hydrogen atmosphere, ZrTiO4 and Ti3+ are formed.•Four orders of magnitude increase in the carrier density was observed for the samples annealed in hydrogen.•25-fold enhancement in the photocurrent was observed for the samples annealed in hydrogen.</description><subject>Anatase</subject><subject>Annealing</subject><subject>Atmosphere</subject><subject>Atmospheres</subject><subject>Carrier density</subject><subject>Coordination compounds</subject><subject>Crystal defects</subject><subject>Crystal structure</subject><subject>Defects</subject><subject>Electronic properties</subject><subject>Hydrogen</subject><subject>Hydrogen storage</subject><subject>Metal oxides</subject><subject>Metals</subject><subject>Multinary metal oxide</subject><subject>Multipodal nanotubes</subject><subject>Nanotechnology</subject><subject>Nanotubes</subject><subject>Niobium</subject><subject>Optical properties</subject><subject>Organic chemistry</subject><subject>Oxides</subject><subject>Oxygen</subject><subject>Photocatalysis</subject><subject>Photocatalysts</subject><subject>Photoelectric effect</subject><subject>Photoelectric emission</subject><subject>Point defects</subject><subject>Raman spectroscopy</subject><subject>Splitting</subject><subject>Structural analysis</subject><subject>Synergistic effect</subject><subject>Tails</subject><subject>Titanium</subject><subject>Transition metal oxides</subject><subject>Transition metals</subject><subject>Valence band</subject><subject>Water splitting</subject><subject>X ray photoelectron spectroscopy</subject><issn>0927-0248</issn><issn>1879-3398</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2019</creationdate><recordtype>article</recordtype><recordid>eNp9kLtOxDAQRS0EEsvCH1BYok7wKw83SGjFS1oJCqgtx5mwjpJ4sR1g_x6jUFNNc-6dmYPQJSU5JbS87vPghlHHnBEqc8JyQukRWtG6khnnsj5GKyJZlREm6lN0FkJPCGElFytkXnYuOhjARO_MDkZr9IC_dASPw36wMdrpHTcH3EKXmIDthCc9uRD9bOLsocXjPCRI-wOOXk_BRusmPEJMPe7bthDO0UmnhwAXf3ON3u7vXjeP2fb54Wlzu80M5yJmrCKUSC4YAd4VRcOhLmsNotaNoU1VNA2TDaGm5Dxdb7QWZVsZWVWUCSaZ4Gt0tfTuvfuYIUTVu9lPaaVijBVMpFiRKLFQxrsQPHRq7-2YzleUqF-dqleLTvWrUxGmks4Uu1likD74tOBVMBYmA631SYxqnf2_4Ad4qIGh</recordid><startdate>20190601</startdate><enddate>20190601</enddate><creator>Fawzy, Samar M.</creator><creator>Omar, Mostafa M.</creator><creator>Allam, Nageh K.</creator><general>Elsevier B.V</general><general>Elsevier BV</general><scope>AAYXX</scope><scope>CITATION</scope><scope>7SP</scope><scope>7ST</scope><scope>7TB</scope><scope>7U5</scope><scope>8FD</scope><scope>C1K</scope><scope>FR3</scope><scope>L7M</scope><scope>SOI</scope></search><sort><creationdate>20190601</creationdate><title>Photoelectrochemical water splitting by defects in nanostructured multinary transition metal oxides</title><author>Fawzy, Samar M. ; Omar, Mostafa M. ; Allam, Nageh K.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c334t-2701093420e3f55b3e868ae48abc1b75bb29b01c633002caa46d7c97712429243</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2019</creationdate><topic>Anatase</topic><topic>Annealing</topic><topic>Atmosphere</topic><topic>Atmospheres</topic><topic>Carrier density</topic><topic>Coordination compounds</topic><topic>Crystal defects</topic><topic>Crystal structure</topic><topic>Defects</topic><topic>Electronic properties</topic><topic>Hydrogen</topic><topic>Hydrogen storage</topic><topic>Metal oxides</topic><topic>Metals</topic><topic>Multinary metal oxide</topic><topic>Multipodal nanotubes</topic><topic>Nanotechnology</topic><topic>Nanotubes</topic><topic>Niobium</topic><topic>Optical properties</topic><topic>Organic chemistry</topic><topic>Oxides</topic><topic>Oxygen</topic><topic>Photocatalysis</topic><topic>Photocatalysts</topic><topic>Photoelectric effect</topic><topic>Photoelectric emission</topic><topic>Point defects</topic><topic>Raman spectroscopy</topic><topic>Splitting</topic><topic>Structural analysis</topic><topic>Synergistic effect</topic><topic>Tails</topic><topic>Titanium</topic><topic>Transition metal oxides</topic><topic>Transition metals</topic><topic>Valence band</topic><topic>Water splitting</topic><topic>X ray photoelectron spectroscopy</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Fawzy, Samar M.</creatorcontrib><creatorcontrib>Omar, Mostafa M.</creatorcontrib><creatorcontrib>Allam, Nageh K.</creatorcontrib><collection>CrossRef</collection><collection>Electronics & Communications Abstracts</collection><collection>Environment Abstracts</collection><collection>Mechanical & Transportation Engineering Abstracts</collection><collection>Solid State and Superconductivity Abstracts</collection><collection>Technology Research Database</collection><collection>Environmental Sciences and Pollution Management</collection><collection>Engineering Research Database</collection><collection>Advanced Technologies Database with Aerospace</collection><collection>Environment Abstracts</collection><jtitle>Solar energy materials and solar cells</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Fawzy, Samar M.</au><au>Omar, Mostafa M.</au><au>Allam, Nageh K.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Photoelectrochemical water splitting by defects in nanostructured multinary transition metal oxides</atitle><jtitle>Solar energy materials and solar cells</jtitle><date>2019-06-01</date><risdate>2019</risdate><volume>194</volume><spage>184</spage><epage>194</epage><pages>184-194</pages><issn>0927-0248</issn><eissn>1879-3398</eissn><abstract>Point defects play a crucial role in the performance of functional materials. The most important extrinsic elements for point defects in titanium-based photocatalysts are oxygen, nitrogen, and hydrogen due to their large chemical affinity and substantial solubility with titanium. Therefore, understanding the nature of such defects will help designing high-performance photocatalysts for various applications. Herein, we make use of alloyed multipodal Ti-Nb-Zr-O nanotubes (MPNTs) annealed under different atmospheres: Air, O2, and H2 for enhanced photoelectrochemical water-splitting. Structural analysis using XRD, Raman spectroscopy, and XPS confirmed the formation of a single mixed oxide Ti-Nb-Zr-O in a strained-anatase crystal structure in both Air and Oxygen atmospheres. However, XPS fitting showed the presence of ZrTiO4 and Ti3+ upon annealing in Hydrogen atmosphere. Valence band XPS analysis confirms the presence of valence band tail states causing band-gap reduction in the hydrogen-annealed samples, with an absorption tail reaching NIR/Vis region. Mott-Schottky analysis showed 4 orders of magnitude increase in the carrier density for the samples annealed in hydrogen atmosphere compared to those annealed in Air or O2, owing to the presence of Ti3+ defects/oxygen vacancies, titanium substitution by niobium, and the valence band tail states. These synergistic effects resulted in almost 25-fold enhancement in the photocurrent compared to the performance of the samples annealed in Oxygen or Air. It is thus concluded that annealing in a reducing atmosphere produces disordered and defective structure. Accordingly, the optical and electronic properties of complex metal oxides exhibiting poor performance can be manipulated to produce promising candidates for enhanced photoelectrochemical water splitting.
[Display omitted]
•Point defects controlled the photocatalytic performance of multinary metal oxides.•Strained single mixed oxide is formed upon annealing in both Air and Oxygen.•Upon annealing Hydrogen atmosphere, ZrTiO4 and Ti3+ are formed.•Four orders of magnitude increase in the carrier density was observed for the samples annealed in hydrogen.•25-fold enhancement in the photocurrent was observed for the samples annealed in hydrogen.</abstract><cop>Amsterdam</cop><pub>Elsevier B.V</pub><doi>10.1016/j.solmat.2019.02.011</doi><tpages>11</tpages></addata></record> |
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| subjects | Anatase Annealing Atmosphere Atmospheres Carrier density Coordination compounds Crystal defects Crystal structure Defects Electronic properties Hydrogen Hydrogen storage Metal oxides Metals Multinary metal oxide Multipodal nanotubes Nanotechnology Nanotubes Niobium Optical properties Organic chemistry Oxides Oxygen Photocatalysis Photocatalysts Photoelectric effect Photoelectric emission Point defects Raman spectroscopy Splitting Structural analysis Synergistic effect Tails Titanium Transition metal oxides Transition metals Valence band Water splitting X ray photoelectron spectroscopy |
| title | Photoelectrochemical water splitting by defects in nanostructured multinary transition metal oxides |
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