Insights into the Effects of Surface/Bulk Defects on Photocatalytic Hydrogen Evolution over TiO2 with Exposed {001} Facets
TL;DR: In this paper, the authors describe the effects of defect distribution on energy band structure and subsequent photocatalytic activity over TiO2 with exposed {001} facets as the model catalyst.
Abstract: This paper describes the effects of defect distribution on energy band structure and the subsequent photocatalytic activity over TiO2 with exposed {001} facets as the model catalyst. Our results show that only surface oxygen vacancies (Vo’s) and Ti3+ centers in TiO2 can be induced by hydrogenation treatment, whereas the generation of bulk Vo’s and Ti3+ species depends on the thermal treatment in nitrogen. Both the surface and bulk defects in TiO2 can promote the separation of electron-hole pairs, enhance the light absorption, and increase the donor density. The presence of surface and bulk defects in TiO2 can not change the valence band maximum, but determine the conduction band minimum. Surface defects in TiO2 induce a tail of conduction band located above the H+/H2 redox potential, which benefits the photocatalytic performance. However, bulk defects in TiO2 generate a band tail below the H+/H2 potential, which inhibits hydrogen production. Thus, the change of band gap structure by defects is the major factor to determine the photocatalytic activity of TiO2 for hydrogen evolution. It is a new insight into the rational design and controllable synthesis of defect-engineered materials for various catalytic processes.
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TL;DR: In this paper, the state-of-the-art progress on defect-engineered photocatalytic materials is reviewed and the future opportunities and challenges regarding defect engineering in photocatalysis are highlighted.
629 citations
TL;DR: Experimental results and density functional theory calculations demonstrate that Pt-O-Ti 3+ atomic interface effectively facilitates photogenerated electrons to transfer from Ti 3+ defective sites to single Pt atoms, thereby enhancing the separation of electron-hole pairs.
Abstract: It is highly desirable but challenging to optimize the structure of photocatalysts at the atomic scale to facilitate the separation of electron-hole pairs for enhanced performance. Now, a highly efficient photocatalyst is formed by assembling single Pt atoms on a defective TiO2 support (Pt1 /def-TiO2 ). Apart from being proton reduction sites, single Pt atoms promote the neighboring TiO2 units to generate surface oxygen vacancies and form a Pt-O-Ti3+ atomic interface. Experimental results and density functional theory calculations demonstrate that the Pt-O-Ti3+ atomic interface effectively facilitates photogenerated electrons to transfer from Ti3+ defective sites to single Pt atoms, thereby enhancing the separation of electron-hole pairs. This unique structure makes Pt1 /def-TiO2 exhibit a record-level photocatalytic hydrogen production performance with an unexpectedly high turnover frequency of 51423 h-1 , exceeding the Pt nanoparticle supported TiO2 catalyst by a factor of 591.
311 citations
TL;DR: In this article, a facile low-temperature solvothermal method by using Li-dissolved ethanediamine to prepare uniform hydrogenated blue H-TiO2-x with wide spectrum response was reported.
Abstract: Here we report a facile low-temperature solvothermal method by using Li-dissolved ethanediamine to prepare uniform hydrogenated blue H-TiO2–x with wide spectrum response. H-TiO2–x possesses a distinct crystalline core–amorphous shell structure (TiO2@TiO2–x) with numerous oxygen vacancies and doped H in the amorphous shell. Efficient solar to chemical energy conversions, likely photocatalytic reduction of CO2, degradation of contaminants, and H2 generation from water splitting can be achieved over this blue titania. Notably, the optimized H-TiO2–x(200) shows high activity of CH4 formation at a rate of 16.2 μmol g–1 h–1 and a selectivity of 79% under full solar irradiation. The kinetic isotope effects measurements reveal that the cleavage of the C═O bond from CO2 rather than the O–H bond from H2O is the rate-determining step in CH4 formation. Meanwhile, in situ diffuse reflectance infrared Fourier transform spectroscopy shows the existence of the key intermediate CO2– species. The formation of intermediate ...
206 citations
TL;DR: In this article, the Co3O4 quantum dots (QDs)/TiO2 nanobelts (NBs) hybrid was constructed via a facile hydrothermal method for simultaneous H2 and O2 productions from pure water, with high evolution rates of 41.8 and 22.0
Abstract: Solar-light driven water splitting to hydrogen and oxygen without sacrificial agents has gained tremendous attention due to the clean and renewable energy supply of the future. Herein, we report construction of Co3O4 quantum dots (QDs)/TiO2 nanobelts (NBs) hybrids via a facile hydrothermal method for simultaneous H2 and O2 productions from pure water, with high evolution rates of 41.8 and 22.0 μmol h−1 g−1, respectively, which are significantly enhanced compared with TiO2 NBs and Co3O4 materials. The Co3O4 QDs not only improve light sensitivity but also change the work function of TiO2, promoting the transfer of electrons from TiO2 to Co3O4 QDs and H2 generation on the surface of Co3O4 QDs. Moreover, the size effect of Co3O4 QDs (∼3 nm) facilitates the electron trapping due to the shorter pathway, and the generation of heterojunctions favors to suppress the recombination of photo-excited carries.
198 citations
TL;DR: This work comprehensively reviews point defective metal‐based photocatalysts for water splitting, focusing on understanding the defects' disorder effect on optical adsorption, charge separation and migration, and surface reaction.
Abstract: Photocatalytic water splitting is promising for hydrogen energy production using solar energy and developing highly efficient photocatalysts is challenging. Defect engineering is proved to be a very useful strategy to promote the photocatalytic performance of metal-based photocatalysts, however, the vital role of defects is still ambiguous. This work comprehensively reviews point defective metal-based photocatalysts for water splitting, focusing on understanding the defects' disorder effect on optical adsorption, charge separation and migration, and surface reaction. The controllable synthesis and tuning strategies of defective structure to improve the photocatalytic performance are summarized, then the characterization techniques and density functional theory calculations are discussed to unveil the defect structure, and analyze the defects induced electronic structure change of catalysts and its ultimate effect on the photocatalytic activity at the molecular level. Finally, the challenge in developing more efficient defective metal-based photocatalysts is outlined. This work may help further the understanding of the fundamental role of defect structure in the photocatalytic reaction process and guide the rational design and fabrication of highly efficient and low-cost photocatalysts.
198 citations
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9,432 citations
TL;DR: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent.
Abstract: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)
8,850 citations
TL;DR: Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting and its Applications d0 Metal Oxide Photocatalysts 6518 4.4.1.
Abstract: 2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519
6,332 citations
TL;DR: It is shown that disorder-engineered TiO2 nanocrystals exhibit substantial solar-driven photocatalytic activities, including the photo-oxidation of organic molecules in water and the production of hydrogen with the use of a sacrificial reagent.
Abstract: When used as a photocatalyst, titanium dioxide (TiO(2)) absorbs only ultraviolet light, and several approaches, including the use of dopants such as nitrogen, have been taken to narrow the band gap of TiO(2). We demonstrated a conceptually different approach to enhancing solar absorption by introducing disorder in the surface layers of nanophase TiO(2) through hydrogenation. We showed that disorder-engineered TiO(2) nanocrystals exhibit substantial solar-driven photocatalytic activities, including the photo-oxidation of organic molecules in water and the production of hydrogen with the use of a sacrificial reagent.
5,217 citations
TL;DR: This work synthesized uniform anatase TiO2 single crystals with a high percentage (47 per cent) of {001} facets using hydrofluoric acid as a morphology controlling agent and demonstrates that for fluorine-terminated surfaces this relative stability is reversed.
Abstract: [Yang, Hua Gui; Sun, Cheng Hua; Qiao, Shi Zhang; Liu, Gang; Smith, Sean Campbell; Lu, Gao Qing] Univ Queensland, ARC Ctr Excellence Funct Nanomat, Sch Engn, Brisbane, Qld 4072, Australia. [Yang, Hua Gui; Sun, Cheng Hua; Qiao, Shi Zhang; Liu, Gang; Smith, Sean Campbell; Lu, Gao Qing] Univ Queensland, Australian Inst Bioengn & Nanotechnol, Ctr Computat Mol Sci, Brisbane, Qld 4072, Australia. [Zou, Jin] Univ Queensland, Ctr Microscopy & Microanal, Brisbane, Qld 4072, Australia. [Zou, Jin] Univ Queensland, Sch Engn, Brisbane, Qld 4072, Australia. [Liu, Gang; Cheng, Hui Ming] Chinese Acad Sci, Met Res Inst, Shenyang Natl Lab Mat sci, Shenyang 110016, Peoples R China.;Lu, GQ (reprint author), Univ Queensland, ARC Ctr Excellence Funct Nanomat, Sch Engn, Brisbane, Qld 4072, Australia;s.qiao@uq.edu.au maxlu@uq.edu.au
3,656 citations