Magnéli Phases Doped with Pt for Photocatalytic Hydrogen Evolution

Abstract

Defined substoichiometric titanium oxides (TixO2x-1 with 3 ≤ x ≤ 10) called Magnéli phases have been investigated mostly for their unusual high conductivity and metal-like behavior. In photocatalysis, Magnéli phase containing titania particles have been reported to provide favorable charge separation resulting in enhanced reaction efficiency. In the current work we describe a onestep synthesis of Magnéli-containing mixed phase nanoparticles that carry directly integrated minute amounts of Pt. Phase optimized nanoparticles that contain only a few hundred ppm Pt are very effective photocatalysts for H2 evolution (they provide a 50-100 times higher H2 evolution than plain anatase loaded with a similar amount of Pt). These photocatalysts are synthesized in a setup combining a hot-wall reactor that is used for TiOx synthesis with a spark generator producing Pt nanoparticles. Different reactor temperatures result in various phase ratios between anatase and Magnéli phases. The titania nanoparticles (≈ 24 -53 nm) were characterized using XRD, HRTEM, XPS and EPR spectra as well as ICP-OES analysis. The best photocatalyst prepared at 900 ºC (which consists of mixed phase particles of 32% anatase, 11% rutile and 57% Magnéli phases loaded with 290 ppm of Pt) can provide a photocatalytic H2 evolution rate of ≈ 5432 μmol h −1 g −1

Ultra-stable self-standing Au nanowires/TiO2nanoporous membrane system for high-performance photoelectrochemical water splitting cells

“…It is very well known, especially from photocatalytic (PC) studies on H 2 evolutions, that the most common and efficient approach of titania modification is coupling with noble metal cocatalysts such as Pt, Ag, Au [6][7][8][9] or their alloys. 10 Coupling of TiO 2 surface with noble metals typically results in a very high efficiency of PC and PEC processes, assigned to several different effects such as Schottky barrier (SB) formation, 11,12 co-catalytic properties, or surface plasmon resonance (SPR).…”

Reduced TiO2 nanotube array as an excellent cathode for hydrogen evolution reaction in alkaline solution

“…Another reason could be the formation of quasi-metallic titania TiO x (pathway➁). Quasi-metallic reduced TiO x , such as the Magnéli phase, has been known for its low resistance comparable to conductors and exist in partially reduced Ti oxides [42][43][44]. The XRD pattern of R-TNT sample shows that the locations of all the peaks are the same with those in the pattern of TNT.…”

Long‐Term Stability of Light‐Induced Ti3+ Defects in TiO2 Nanotubes for Amplified Photoelectrochemical Water Splitting

“…[3,5] The improved PC activity of the surface-reduced material is due to an extra electronic state of Ti 3 + located slightly below the conduction band of titania, which traps electrons and mediates their transfer at the interface with an electrolyte. [6] On the other hand, PEC processes benefit from the improved conductivity [5,7,8] and much higher carrier density that result from the presence of Ti 3 + states. [9] Another aspect of the reductive treatment is forming an amorphous shell or disordered surface layer, which was initially identified as the cause of the improved PC/PEC activity.…”