skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Noble metal free photocatalytic H 2 generation on black TiO 2: On the influence of crystal facets vs. crystal damage

Abstract

In this study, we investigate noble metal free photocatalytic water splitting on natural anatase single crystal facets and on wafer slices of the [001] plane before and after these surfaces have been modified by high pressure hydrogenation and hydrogen ion-implantation. Here, we find that on the natural, intact low index planes, photocatalytic H 2 evolution (in the absence of a noble metal co-catalyst) can only be achieved when the hydrogenation treatment is accompanied by the introduction of crystal damage, such as simple scratching and miscut in the crystal, or by implantation damage. X-ray reflectivity, Raman, and optical reflection measurements show that plain hydrogenation leads to a ≈ 1 nm thick black titania surface layer without activity, while a colorless, density modified, and ≈7 nm thick layer with broken crystal symmetry is present on the ion implanted surface. These results demonstrate that (i) the H-treatment of an intact anatase surface needs to be combined with defect formation for catalytic activation and (ii) activation does not necessarily coincide with the presence of black color.

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Univ. of Erlangen-Nuremberg, Erlangen (Germany). Inst. for Surface Science and Corrosion (LKO), Dept. of Materials Science WW-4
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL), Materials Science Division
  3. Univ. of Erlangen-Nuremberg, Erlangen (Germany). Inst. for Surface Science and Corrosion (LKO), Dept. of Materials Sciences 6
  4. Univ. of Erlangen-Nuremberg, Erlangen (Germany). Inst. for Surface Science and Corrosion (LKO), Dept. of Materials Science WW-4; Univ. of Erlangen-Nuremberg, Erlangen (Germany). Inst. of Biomaterials
  5. Univ. of Erlangen-Nuremberg, Erlangen (Germany). Inst. for Surface Science and Corrosion (LKO), Dept. of Materials Science WW-4; King Abdulaziz Univ., Jeddah (Saudi Arabia). Dept. of Chemistry
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1353174
Grant/Contract Number:
AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 110; Journal Issue: 7; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Ion implantation; Electron densities of states; Crystal defects; Single crystals; High pressure

Citation Formats

Liu, Ning, Steinrück, Hans-Georg, Osvet, Andres, Yang, Yuyun, and Schmuki, Patrik. Noble metal free photocatalytic H2 generation on black TiO2: On the influence of crystal facets vs. crystal damage. United States: N. p., 2017. Web. doi:10.1063/1.4976010.
Liu, Ning, Steinrück, Hans-Georg, Osvet, Andres, Yang, Yuyun, & Schmuki, Patrik. Noble metal free photocatalytic H2 generation on black TiO2: On the influence of crystal facets vs. crystal damage. United States. doi:10.1063/1.4976010.
Liu, Ning, Steinrück, Hans-Georg, Osvet, Andres, Yang, Yuyun, and Schmuki, Patrik. Mon . "Noble metal free photocatalytic H2 generation on black TiO2: On the influence of crystal facets vs. crystal damage". United States. doi:10.1063/1.4976010. https://www.osti.gov/servlets/purl/1353174.
@article{osti_1353174,
title = {Noble metal free photocatalytic H2 generation on black TiO2: On the influence of crystal facets vs. crystal damage},
author = {Liu, Ning and Steinrück, Hans-Georg and Osvet, Andres and Yang, Yuyun and Schmuki, Patrik},
abstractNote = {In this study, we investigate noble metal free photocatalytic water splitting on natural anatase single crystal facets and on wafer slices of the [001] plane before and after these surfaces have been modified by high pressure hydrogenation and hydrogen ion-implantation. Here, we find that on the natural, intact low index planes, photocatalytic H2 evolution (in the absence of a noble metal co-catalyst) can only be achieved when the hydrogenation treatment is accompanied by the introduction of crystal damage, such as simple scratching and miscut in the crystal, or by implantation damage. X-ray reflectivity, Raman, and optical reflection measurements show that plain hydrogenation leads to a ≈ 1 nm thick black titania surface layer without activity, while a colorless, density modified, and ≈7 nm thick layer with broken crystal symmetry is present on the ion implanted surface. These results demonstrate that (i) the H-treatment of an intact anatase surface needs to be combined with defect formation for catalytic activation and (ii) activation does not necessarily coincide with the presence of black color.},
doi = {10.1063/1.4976010},
journal = {Applied Physics Letters},
number = 7,
volume = 110,
place = {United States},
year = {Mon Feb 13 00:00:00 EST 2017},
month = {Mon Feb 13 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 1work
Citation information provided by
Web of Science

Save / Share:
  • Graphane, graphone and hydrogenated graphene (HG) have been extensively studied in recent years due to their interesting properties and potential use in commercial and industrial applications. The present study reports investigation of hydrogenated graphene/TiO 2-x (HGT) nanocomposites as photocatalysts for H 2 and O 2 production from water without the assistance of a noble metal co-catalyst. By combination of several techniques, the morphologies, bulk/atomic structure and electronic properties of all the powders were exhaustively interrogated. Hydrogenation treatment efficiently reduces TiO 2 nanoparticles, while the graphene oxide sheets undergo the topotactic transformation from a graphene-like structure to a mixture of graphiticmore » and turbostratic carbon (amorphous/disordered) upon altering the calcination atmosphere from a mildly reducing to a H 2-abundant environment. Remarkably, the hydrogenated graphene-TiO 2-x composite that results upon H 2-rich reduction exhibits the highest photocatalytic H 2 evolution performance equivalent to low loading of Pt (~0.12 wt%), whereas the addition of HG suppresses the O 2 production. As a result, we propose that such an enhancement can be attributed to a combination of factors including the introduction of oxygen vacancies and Ti 3+ states, retarding the recombination of charge carriers and thus, facilitating the charge transfer from TiO 2-x to the carbonaceous sheet.« less
  • Introducing defects into semiconductors with well-controlled exposed facets offers an effective route for the development of photocatalytic materials with greatly improved properties. Here, we report a facile ethylene glycol reduction procedure to make anatase titanium dioxide (TiO 2) with different concentrations of exposed {001} and {101} facets, leading to different surficial defects. TiO 2 with increased concentrations of {101} facets shows a 5-fold improvement in photocurrent generation as well as improved photocatalytic activity towards water splitting under visible light irradiation. Thus, the improved activity is ascribed to the oxygen vacancies as well as the variable surface chemical states, which collectivelymore » induce a slower recombination rate of photo-induced electron-hole pairs. This work also highlights a feasible strategy to obtain the defective TiO 2 and explore the synergistic effect of surface defects and different concentrations of exposed {001} and {101} facets for photocurrent and photocatalytic properties under visible light irradiation.« less
  • The complete photocatalytic oxidation of C{sub 2}H{sub 4} with O{sub 2} into CO{sub 2} and H{sub 2}O has been achieved on ultrafine powdered TiO{sub 2} photocatalysts and the addition of H{sub 2}O was found to enhance the reaction. The details of the photocatalytic reaction have been studied by IR, ESR, and analysis of the reaction products. UV irradiation of the photocatalysts at 275 K led to the photocatalytic oxidation of C{sub 2}H{sub 4} with O{sub 2} into CO{sub 2}, CO, and H{sub 2}O. The large surface area of the photocatalyst is one of the most important factors in achieving amore » high efficiency in the photocatalytic oxidation of C{sub 2}H{sub 4}. The photo-formed OH species as well as O{sub 2}{sup {minus}} and O{sub 3}{sup {minus}} anion radicals play a significant role as a key active species in the complete photocatalytic oxidation of C{sub 2}H{sub 4} with O{sub 2} into CO{sub 2} and H{sub 2}O.« less
  • Highlights: • A hydrogen evolution reaction of g-C{sub 3}N{sub 4}/MoS{sub 2}/TiO{sub 2} photocatalyst was synthesized. • g-C{sub 3}N{sub 4}/MoS{sub 2}/TiO{sub 2} presents highly efficient H{sub 2} evolution without noble metals. • The effect of g-C{sub 3}N{sub 4} and MoS{sub 2} co-catalyst content in the composites was studied. • The mechanism of g-C{sub 3}N{sub 4}/MoS{sub 2}/TiO{sub 2} photocatalyst under UV–vis light was discussed. - Abstract: In this paper, we report a new g-C{sub 3}N{sub 4}/MoS{sub 2}/TiO{sub 2} composite material as a high-performance photocatalyst for H{sub 2} evolution. Without a noble-metal cocatalyst, the g-C{sub 3}N{sub 4}/MoS{sub 2}/TiO{sub 2} composite reaches a highmore » H{sub 2} production rate of 125 μmol h{sup −1} when the content of the g-C{sub 3}N{sub 4}/MoS{sub 2} cocatalyst is 1.0 wt.% and the content of g-C{sub 3}N{sub 4} in this cocatalyst is 10 wt.%. This unusual photocatalytic activity is attributed to the positive synergetic effect between the MoS{sub 2} and g-C{sub 3}N{sub 4} components in this cocatalyst, which serve as an electron collector and a source of active adsorption sites, respectively.« less
  • Graphical abstract: The La{sub 2}O{sub 3}/TiO{sub 2}-900 °C (or La{sub 2}O{sub 3}/Ti(OH){sub 4}-900 °C), with surface anatase phase, show the similar photocatalytic activity. The presence of the surface anatase phase is important for high photocatalytic activity of TiO{sub 2} modified with La{sub 2}O{sub 3} (La{sub 2}O{sub 3}/Ti(OH){sub 4}-900 °C or La{sub 2}O{sub 3}/Ti(OH){sub 4}-900 °C){sub .} - Highlights: • Loading La{sub 2}O{sub 3} on anatase TiO{sub 2} is an effective method for stabilizing the anatase phases both in the surface and in the bulk region. • The high crystallinity of the surface anatase phase is important for high photocatalytic activitymore » of TiO{sub 2} modified with La{sub 2}O{sub 3.} - Abstract: TiO{sub 2} nanoparticles modified with La{sub 2}O{sub 3} were prepared by an impregnation method using anatase TiO{sub 2} support (La{sub 2}O{sub 3}/TiO{sub 2}) or amorphous Ti(OH){sub 4} support (La{sub 2}O{sub 3}/Ti(OH){sub 4}). The bulk and surface crystalline phases of La{sub 2}O{sub 3}/TiO{sub 2} (or La{sub 2}O{sub 3}/Ti(OH){sub 4}) have been characterized by X-ray powder diffraction (XRD) and UV Raman spectroscopy. Besides, morphology and particle size of La{sub 2}O{sub 3}/TiO{sub 2} and La{sub 2}O{sub 3}/Ti(OH){sub 4} samples have been determined by TEM (transmission electron microscope) and Brunauer–Emmett–Teller (BET), respectively. It is found that the phase transformation and increase of the particle size of TiO{sub 2} can be more effectively inhibited in the La{sub 2}O{sub 3}/TiO{sub 2} than in the La{sub 2}O{sub 3}/Ti(OH){sub 4}. Photocatalytic experiments indicated that the La{sub 2}O{sub 3}/TiO{sub 2} (or La{sub 2}O{sub 3}/Ti(OH){sub 4}) samples with surface anatase phase have the similar overall photocatalytic activities. Moreover, it is found that the high crystallinity of surface anatase phase is benefit for the high photocatalytic activity of TiO{sub 2} modified with La{sub 2}O{sub 3}.« less