Nickel Oxide Selectively Deposited on the {101} Facet of Anatase TiO₂ Nanocrystal Bipyramids for Enhanced Photocatalysis

Abstract

Facet-engineered anatase TiO2 with NiO nanoparticles heterocontacts were successfully prepared by selective photodeposition of NiO nanoparticles onto the {101} facet of the top-truncated bipyramidal TiO2 anatase nanocrystals coexposed with {001} and {101} facets. The morphology and electronic properties of the resulting 0.1–10 wt % NiO-decorated TiO2 were investigated by X-ray diffraction, high-resolution electron microscopy, N2 sorption analysis, and UV–vis spectroscopy. Furthermore, a careful determination of the energy band alignment diagram was conducted by a model experiment using XPS and UPS to verify charge separation at the interface of the NiO−TiO2 heterostructure. The model experiment was performed by stepwise deposition of NiO onto oriented TiO2 substrates and in-situ photoelectron spectroscopy measurements without breaking vacuum. Core levels showed shifts of 0.58 eV toward lower binding energies, meaning an upward band bending in TiO2 at the NiO–TiO2 interface. Furthermore, 0.1 wt % NiO–TiO2 exhibited 50% higher activities than the pure TiO2 for methylene blue (MB) photodecomposition under UV irradiation. This enhanced photocatalytic activity of NiO–TiO2 nanocomposites was related to the internal electric field developed at the p–n NiO−TiO2 heterojunction, leading to vectorial charge separation. Finally, mechanistic studies conducted in the presence of carrier or radical scavengers revealed that holes dominantly contributed to the photocatalytic reactions in the case of NiO–TiO2 photocatalysts while electrons played the main role in photocatalysis for the pure TiO2 materials.

Sunlight Selective Photodeposition of CoOx(OH)y and NiOx(OH)y on Truncated Bipyramidal BiVO4 for Highly Efficient Photocatalysis

“…Furthermore, free radical trap experiments were conducted using a previously reported procedure (see ESI). 46 The sacrificial photochemical water oxidation tests were carried out under an argon atmosphere with exclusion of air. Solvents were distilled under an argon atmosphere, or degassed via standard procedures prior to use and stored under argon.…”

“…44 However, the dependence of the photodeposition as a function of the cocatalyst amount has not been studied in detail in particular due to the fact of the limitations of FESEM coupled to energy dispersive X-ray spectroscopy (EDS) analyses. Moreover, even though the photodeposition of nickel based compounds has been successfully achieved onto different semiconductors such as CdS, 45 TiO2, 46 or even BiVO4 films, 47 the regioselective deposition of nickel based oxides onto faceted BiVO4 crystals has not been envisaged so far, despite the interest of this co-catalyst for photocatalytic purposes. 26,47 We have recently reported interface experiments showing that strong upwards band bending was observed for CoOx/BiVO4 and NiO/BiVO4 interfaces indicating that this kind of heterostructures should favor charge carrier separation.…”

Synergistic Cyanamide Functionalization and Charge-Induced Activation of Nickel/Carbon Nitride for Enhanced Selective Photoreforming of Ethanol

“…Figure 3a shows the time-dependent H 2 evolution profiles for NCN-CN with various Ni 2+ 36 With the increase in Ni 2+ concentration, the H 2 and acetaldehyde productivities were found to be significantly improved, as shown in Figure 3b. Details on "other" carbon product distributions, including acetic acid, CO 2 , CH 4 , CO, and C 2 H 4 , can be found in Table S3.…”

Anatase TiO2 with Co‐exposed (001) and (101) Surface‐Based Photocatalytic Materials for Energy Conversion and Environmental Purification

“…Its main function was acting as a water oxidation assistant catalyst to capture the holes transferred from the heterojunction formed on the (101) and (001) surfaces, inhibit the recombination of space charges, and thereby improve the photocatalytic activity of (001)-(101)-TiO 2 . Shun Kashiwaya et al [53] prepared (001)-(101)-TiO 2 /NiO composite material by photo-deposition, with a p-n type heterojunction formed by NiO and (101) surface. The surface structure and promotion mechanism of (001)-(101)-TiO 2 /NiO via the in-situ interface simulation experiment was also explored.…”