Interfacial band alignment for photocatalytic charge separation in TiO₂nanotube arrays coated with CuPt nanoparticles

Abstract

n-Type anatase-phase one-dimensional TiO2 nanostructure arrays coated with nanoparticles of Cu or CuPt have emerged as high performance photocatalysts for both photooxidation and photoreduction. The properties of the catalyst-promoter interface are recognized to be critical to this high performance but are largely unknown. Using X-ray and ultraviolet photoelectron spectroscopies (XPS/UPS), we probed the electronic properties of the CuPt-TiO2 interface in transparent TiO2 nanotube arrays (TTNTAs) coated with photodeposited CuPt nanoparticles (CuPt-TTNTA hybrids) as well as those coated with sputtered CuPt (Sput-CuPt-TTNTA hybrids). XPS and UPS spectra provided the evidence of a Schottky barrier with a band-bending of 0.49-0.67 eV at the CuPt-TiO2 interface in CuPt-TTNTA hybrids due to which photoexcited electrons are expected to be retained in the TiO2 while photoexcited holes will be collected by the CuPt nanoparticles. For Sput-CuPt-TTNTA hybrids, no such band-bending was observed. These results point to the importance of the metal nanoparticle preparation technique on interfacial band-alignments and challenge the conventional understanding of the promoting action of noble metal nanoparticles on TiO2 photocatalysts as sinks for photoexcited electrons.

Surface Wettability of ZnO-Loaded TiO2 Nanotube Array Layers

“…Preliminary characterization of the ZnO/TiO 2 heterostructures was done here by deriving the position of the valence band maxima ( Figure 5 ). The valence band maximum (VBM) of the bare TiO 2 layer is located at 3.25 eV below the Fermi level, in agreement with the literature [ 47 ], while the VBM of the heterostructure is located at 2.3 eV below the Fermi level, irrespective of the ZnO coverage. Therefore, only one VB-XPS spectrum for the loaded samples was introduced ( Figure 5 b).…”

“…Apart from the elemental and chemical information on core-level photoelectron lines, the XPS technique allows additional investigation of band gap and valence band localization and structure, despite not being as complete as the ultraviolet photoelectron spectroscopy (UPS) [ 46 , 47 ].…”

Tunable syngas production from photocatalytic CO2 reduction with mitigated charge recombination driven by spatially separated cocatalysts

“…S1a † ), a photodeposition method (Fig. S7 † ) was adopted 29 under the protection of a N 2 atmosphere in methanolic solvent, using platinum acetylacetonate and copper acetylacetonate as precursors. Energy dispersive spectroscopy (EDS) mapping ( Fig.…”

Platinum‐ and CuOx‐Decorated TiO2 Photocatalyst for Oxidative Coupling of Methane to C2 Hydrocarbons in a Flow Reactor

“…These nanoparticles were further identified by HRTEM (Figure 1 e), in which the d spacing of lattice fringes could be attributed to Pt (111, 0.226 nm) and anatase TiO 2 (101, 0.350 nm). [27] The copper species were not observed at this resolution, suggesting the existence of smaller clusters. Energy-dispersive X-ray (EDX) mapping showed that Cu and Pt were dispersed homogeneously (Figure 1 f), in good agreement with the XRD results.…”