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Voids in walls of mesoporous TiO2 anatase nanotubes by controlled formation and annihilation of protonated titanium vacancies.

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Title: Voids in walls of mesoporous TiO2 anatase nanotubes by controlled formation and annihilation of protonated titanium vacancies.
Authors: Getz, Marit Norderhaug1 (AUTHOR), Chatzitakis, Athanasios1 (AUTHOR), Liu, Xin1 (AUTHOR), Carvalho, Patricia Almeida2 (AUTHOR), Bjørheim, Tor Svendsen1 (AUTHOR), Norby, Truls1 (AUTHOR) truls.norby@kjemi.uio.no
Source: Materials Chemistry & Physics. Jan2020, Vol. 239, pN.PAG-N.PAG. 1p.
Subjects: Annealing of metals, Nanotubes, Computational chemistry, Chemical engineering, Dye-sensitized solar cells, Titanium, Aqueous electrolytes
Abstract: Amorphous TiO 2 nanotubes (TNTs) grown anodically on Ti metal in aqueous electrolytes show a crystallization behaviour strongly dependent on the atmosphere used during annealing at high temperature. In wet oxidizing conditions, the amorphous TNTs walls transform into relatively large and well crystallized anatase-like domains permeated by prismatic voids. On the other hand, crystallization of the amorphous nanotubes under dry reducing conditions induces nanocrystalline aggregates that do not show prismatic voids and exhibit different electronic properties. Supported by density functional theory calculations, it is argued that the formation or absence of voids can be understood in terms of formation and condensation of protonated titanium vacancies. Tunable morphology through defect chemical engineering as such, enables TNTs with increased surface area and catalytic activity, which find potential application in supercapacitors, sensors, photocatalysis, photoelectrochemistry, and dye-sensitized solar cells. Prismatic voids are formed in TiO 2 nanotube (TNT) walls by high temperature annealing of anodically grown TNTs. This is attributed to formation and condensation of protonated titanium vacancies, in line with computational defect chemistry of TiO 2 under wet conditions. The voids can be annihilated by high temperature annealing under reducing conditions. The tunable morphology can be utilized for increased surface area and adjustable electrocatalytic activity. Image 1 • Prismatic voids are formed in TiO 2 nanotube walls by high temperature annealing. • The voids form due to condensation of protonated titanium vacancies. • The voids are annihilated by high temperature annealing under reducing conditions. • The tunable morphology can be utilized in photoelectrochemistry and energy storage. [ABSTRACT FROM AUTHOR]
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Abstract:Amorphous TiO 2 nanotubes (TNTs) grown anodically on Ti metal in aqueous electrolytes show a crystallization behaviour strongly dependent on the atmosphere used during annealing at high temperature. In wet oxidizing conditions, the amorphous TNTs walls transform into relatively large and well crystallized anatase-like domains permeated by prismatic voids. On the other hand, crystallization of the amorphous nanotubes under dry reducing conditions induces nanocrystalline aggregates that do not show prismatic voids and exhibit different electronic properties. Supported by density functional theory calculations, it is argued that the formation or absence of voids can be understood in terms of formation and condensation of protonated titanium vacancies. Tunable morphology through defect chemical engineering as such, enables TNTs with increased surface area and catalytic activity, which find potential application in supercapacitors, sensors, photocatalysis, photoelectrochemistry, and dye-sensitized solar cells. Prismatic voids are formed in TiO 2 nanotube (TNT) walls by high temperature annealing of anodically grown TNTs. This is attributed to formation and condensation of protonated titanium vacancies, in line with computational defect chemistry of TiO 2 under wet conditions. The voids can be annihilated by high temperature annealing under reducing conditions. The tunable morphology can be utilized for increased surface area and adjustable electrocatalytic activity. Image 1 • Prismatic voids are formed in TiO 2 nanotube walls by high temperature annealing. • The voids form due to condensation of protonated titanium vacancies. • The voids are annihilated by high temperature annealing under reducing conditions. • The tunable morphology can be utilized in photoelectrochemistry and energy storage. [ABSTRACT FROM AUTHOR]
ISSN:02540584
DOI:10.1016/j.matchemphys.2019.121953