Impact of TiO₂-II phase stabilized in anatase matrix by high-pressure torsion on electrocatalytic hydrogen production

Abstract

Horita (2019) Impact of TiO 2-II phase stabilized in anatase matrix by high-pressure torsion on electrocatalytic hydrogen production, Materials

High‐pressure torsion of SiO2 quartz sand: Phase transformation, optical properties, and significance in geology

“…The HPT method is applicable not only to metallic materials 9,10 but also to brittle and hard nonmetallic materials such as oxides (TiO 2 , 11 ZnO, 12 TiO 2 ‐ZnO, 13 Al 2 O 3 , 14,15 BaTiO 3 , 16 ZrO 2 , 17 LiTaO 3 18 ), nitrides, 19 carbides 20,21 and oxynitrides 22 . So far, the HPT method has been utilized for processing nonmetallic materials with two main motivations: (a) fundamental investigation of strain effect on structural and microstructural changes such as phase transformation and oxygen vacancy formation 11–14 ; (b) developing new functional materials with enhanced dielectricity, 16 electrocatalysis, 23 and photocatalysis 11–14,17,22 …”

High-Pressure Torsion of Non-Equilibrium Hydrogen Storage Materials: A Review

“…Photocatalytic water splitting by TiO 2 is another method for hydrogen generation. During the HPT process of the oxide powder, a TiO 2 (anatase) → TiO 2 -II (orthorhombic) phase transformation takes place, resulting in a narrower bandgap, which improves the hydrogen generation rate under visible light [137,138].…”

High-Pressure Phase Transitions in Densely Packed Nanocrystallites of TiO2-II

“…27736), and Fe 2 P . It was demonstrated recently that the TiO 2 -II phase may have promising applications in photocatalytic and electrocatalytic hydrogen generation , and in optical and optoelectronic devices due to its high refractive index . Previous studies show that, under compression up to ∼70 GPa, bulk anatase, rutile, and brookite experience the same transition route from bulk TiO 2 phase → TiO 2 -II phase → baddeleyite phase → TiO 2 -OI phase → TiO 2 -OII phase. − For nanocrystals of titania, the pressure-induced phase transition is dependent on particle size, morphology, and temperature. − For example, anatase nanocrystals with sizes < ∼10 nm transform to an amorphous state at P > 27 GPa and those with sizes between ∼12 and 50 nm transform to the baddeleyite phase at P > 18 GPa .…”

“…However, so far, the high-pressure behavior of nanocrystalline TiO 2 -II has been scarcely studied because of the difficulty in synthesizing nano TiO 2 -II at ambient pressure. Nonetheless, such a knowledge on the phase behavior of nano TiO 2 -II is highly needed for making good use of its material properties for novel applications, such as for photocatalysis and electrocatalysis . Thus, in this work, we used in situ high-pressure (HP) X-ray diffraction (XRD) and HP-Raman spectroscopy to study the structural changes of TiO 2 -II nanocrystallites produced from high-pressure processing.…”

“…9004140 13 ), fluorite, 14 cotunnite (TiO 2 -OII, space group Pnma, ICSD no. 27736 12 ), and Fe 2 P. 15 It was demonstrated recently that the TiO 2 -II phase may have promising applications in photocatalytic and electrocatalytic hydrogen generation 16,17 and in optical and optoelectronic devices due to its high refractive index. 18 Previous studies show that, under compression up to ∼70 GPa, bulk anatase, rutile, and brookite experience the same transition route from bulk TiO 2 phase → TiO 2 -II phase → baddeleyite phase → TiO 2 -OI phase → TiO 2 -OII phase.…”