Facile assembly of Bi2O3/Bi2S3/MoS2n-p heterojunction with layered n-Bi2O3 and p-MoS2 for enhanced photocatalytic water oxidation and pollutant degradation
TL;DR: In this paper, a facile strategy for controllable synthesis of three-component Bi2O3/Bi2S3/MoS2 n-p heterojunction based on the formation of the intermediate Bi 2S3 by coupling Bi 2O3 and MoS2 was reported.
Abstract: As an important half reaction in solar-driven water splitting, it is still a challenging issue to develop low-cost and high efficient photocatalysts for water oxidation process. In this study, we reported a facile strategy for controllable synthesis of three-component Bi2O3/Bi2S3/MoS2 n-p heterojunction based on the formation of the intermediate Bi2S3 by coupling Bi2O3 and MoS2. The Bi2S3 was easily formed due to the strong interaction between Bi3+ and S2− ions with the assistance of the hydrothermal treatment. As a result, the prepared Bi2O3/Bi2S3/MoS2 nanocomposite exhibits enhanced ability of photocatalytic water oxidation (529.1 μmol h−1 g−1cat), which is 1.5 and 12.5 times higher than that of pure Bi2O3 and MoS2, respectively, under simulated solar light irradiation. Furthermore, the photoelectrochemical results reveal that the charge transportation feature and the donor density were apparently enhanced after the introduction of highly conductive layered MoS2, which indicates the enhancement of the photo-response and the improvement of charge separation efficiency.
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20 Aug 2018
TL;DR: Recent topics in nanoscale Bi-based photocatalysts, including doping, changing stoichiometry, solid solutions, ultrathin nanosheets, hierarchical and hollow architectures, conventional heterojunctions, direct Z-scheme junctions, and surface modification of conductive materials and semiconductors, are reviewed.
Abstract: Nanoscale Bi-based photocatalysts are promising candidates for visible-light-driven photocatalytic environmental remediation and energy conversion. However, the performance of bulk bismuthal semiconductors is unsatisfactory. Increasing efforts have been focused on enhancing the performance of this photocatalyst family. Many studies have reported on component adjustment, morphology control, heterojunction construction, and surface modification. Herein, recent topics in these fields, including doping, changing stoichiometry, solid solutions, ultrathin nanosheets, hierarchical and hollow architectures, conventional heterojunctions, direct Z-scheme junctions, and surface modification of conductive materials and semiconductors, are reviewed. The progress in the enhancement mechanism involving light absorption, band structure tailoring, and separation and utilization of excited carriers, is also introduced. The challenges and tendencies in the studies of nanoscale Bi-based photocatalysts are discussed and summarized.
396 citations
TL;DR: In this article, an Ag2O/CeO2 p-n heterojuction photocatalysts were fabricated by an in situ loading Ag2CO3 on CeO2 spindles and subsequent via a thermal decomposition process.
Abstract: Semiconductor photocatalysis has been considered as one of the most promising technologies for the removal of antibiotics from aqueous solutions. In this study, Ag2O/CeO2 p-n heterojuction photocatalysts were fabricated by an in situ loading Ag2CO3 on CeO2 spindles and subsequent via a thermal decomposition process. The Ag2O/CeO2 composites exhibited enhanced photocatalytic activity for the photodegradation of enrofloxacin (EFA) under visible light irradiation. A plausible degradation pathway for EFA was proposed. The Ag2O/CeO2 heterojuction photocatalysts exhibited the high mineralization ability towards the EFA molecule degradation based on three-dimensional excitation–emission matrix fluorescence spectroscopy (3D EEMs) and total organic carbon (TOC) analysis. Transient photocurrent response, PL spectrum and EIS indicate high photoinduced charge separation efficiency possess in Ag2O/CeO2 composites. Active species trapping experiments and ESR technique confirmed that h+ and O2 were the main active groups involved in photo-degradation of organic pollutants. Through the combination of various performance characterization and experimental results, a possible photocatalytic mechanism was proposed. Moreover, the energy band alignments of Ag2O/CeO2 heterostructure were calculated, which provided strong support for the proposed mechanism. This work could provide a new approach to construct new heterojunction photocatalysts and a deeper insight for the heterojunction catalyst.
363 citations
TL;DR: In this article, a cost-effective and eco-friendly calcium-doped α-Fe2O3 was fabricated using a scalable precipitation-calcination method to activate peroxymonosulfate (PMS) for wastewater purification.
Abstract: In this work, a cost-effective and eco-friendly calcium-doped α-Fe2O3 (Ca-Fe2O3) with abundant oxygen vacancies was fabricated using a scalable precipitation-calcination method to activate peroxymonosulfate (PMS) for wastewater purification. Density functional theory calculations revealed that the incorporation of Ca2+ into the α-Fe2O3 structure enhances the electron transfer from α-Fe2O3 to PMS, facilitating the activation of PMS. The degradation of Rhodamine B by 5%Ca-Fe2O3 proceeded with a reaction constant 8 times higher than that of pristine α-Fe2O3. This can be attributed to the increased generation of 1O2 and O2•−, increased specific surface area and enhanced electrical conductivity. The applicability of the 5%Ca-Fe2O3/PMS system was investigated including its operating parameters and stability, and the intermediates involved in the reaction were identified. The 5%Ca-Fe2O3/PMS system exhibited excellent degradation efficiency in natural water samples. This work opens up new perspectives for designing highly efficient catalysts and renders iron oxides potential candidates for environmental remediation.
323 citations
TL;DR: MoS2 quantum dots (MSQDs) with high and stable dispersion in water were prepared via a facile one-pot hydrothermal process as discussed by the authors, and the MSQDs were then applied to decorate graphitic carbon nitride (g-C3N4, CN) nanosheets to obtain modified g-C 3N4 photocatalysts.
Abstract: MoS2 quantum dots (MSQDs) with high and stable dispersion in water were prepared via a facile one-pot hydrothermal process. The MSQDs were then applied to decorate graphitic carbon nitride (g-C3N4, CN) nanosheets to obtain modified g-C3N4 photocatalysts (MSQD-CN). Compared to pristine g-C3N4, the hybrid photocatalysts showed a slight red shift and stronger light absorption with remarkably improved photocatalytic activity in water splitting to generate hydrogen. The hydrogen-evolution rate over 0.2 wt% MSQD-CN increased by 1.3 and 8.1 times as high as that of 0.2 wt% Pt-CN and g-C3N4, respectively. With deposition of 2 wt% Pt as a cocatalyst, 5 wt% MSQD-CN exhibited the highest photocatalytic efficiency with an average hydrogen evolution reaction (HER) rate of 577 μmol h−1 g−1. Photoluminescence spectra (PL) and photoelectrochemical measurements inferred that MSQDs introduction drastically promoted the electron transfer for more efficient separation of charge carriers, which could lower HER overpotential barriers and enhance the electrical conductivity. In addition, the well-matched band potentials of the MSQD-CN hybrid with an intimate contact interface of p-n heterojunction also inhibited the recombination of photo-generated carriers, leading to enhanced photocatalytic HER performance. A direct Z-scheme charge transfer mechanism of the MSQD-CN hybrid was proposed to further elaborate the synergistic effect between MSQDs, Pt and g-C3N4. This work underlines the importance of heterojunction interface and presents a feasible protocol for rational construction of g-C3N4 based photocatalysts for various photocatalytic applications.
280 citations
TL;DR: Wang et al. as mentioned in this paper proposed a method for efficient removal of gaseous chlorinated-volatile organic compounds (VOCs) under simulated sunlight irradiation by using Ag nanoparticles.
Abstract: Ag decorated WO3/Bi2WO6 hybrid heterojunction with a direct Z-scheme band structure has been synthesized by a novel method for efficient removal of gaseous chlorinated-volatile organic compounds (VOCs) under simulated sunlight irradiation. Bismuth atoms were inserted into the [WO6] layers of tungstate acid to form [Bi2O2] layers toward the formation of a Bi2WO6 crystal phase, which results in Z-scheme WO3/Bi2WO6 heterojunction. Ag nanoparticles (NPs) were further introduced and uniformly anchored on the surface of the WO3/Bi2WO6 for improving visible-light absorption and adjusting behavior of photoinduced charge carriers in the heterostructure through surface plasmon resonance (SPR). In comparison with pristine Bi2WO6 and WO3/Bi2WO6, Ag/WO3/Bi2WO6 exhibits a better photocatalytic activity for removal of gaseous chlorobenzene under simulated sunlight irradiation. The conversion efficiency of 2% Ag/WO3/Bi2WO6 heterojunction is 2.5 and 1.9 times higher than those of the pristine Bi2WO6 and WO3/Bi2WO6 samples, respectively. The improved photocatalytic activity is mainly attributed to the formation of three-component heterojunction with the Z-scheme structure and SPR effect of Ag NPs, which could not only increase absorption of visible light, but also promote the separation efficiency of photogenerated electrons and holes in the hybrids.
256 citations
References
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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: This review attempts to summarize the recent progress in the rational design and fabrication ofheterojunction photocatalysts, such as the semiconductor-semiconductor heterojunction, the semiconductors-metal heterojunctions, the silicon-carbon heteroj junction and the multicomponent heteroj conjunction.
Abstract: Semiconductor-mediated photocatalysis has received tremendous attention as it holds great promise to address the worldwide energy and environmental issues. To overcome the serious drawbacks of fast charge recombination and the limited visible-light absorption of semiconductor photocatalysts, many strategies have been developed in the past few decades and the most widely used one is to develop photocatalytic heterojunctions. This review attempts to summarize the recent progress in the rational design and fabrication of heterojunction photocatalysts, such as the semiconductor–semiconductor heterojunction, the semiconductor–metal heterojunction, the semiconductor–carbon heterojunction and the multicomponent heterojunction. The photocatalytic properties of the four junction systems are also discussed in relation to the environmental and energy applications, such as degradation of pollutants, hydrogen generation and photocatalytic disinfection. This tutorial review ends with a summary and some perspectives on the challenges and new directions in this exciting and still emerging area of research.
3,013 citations
TL;DR: The findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for ‘clean’ hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.
Abstract: The photocatalytic splitting of water into hydrogen and oxygen using solar energy is a potentially clean and renewable source for hydrogen fuel. The first photocatalysts suitable for water splitting, or for activating hydrogen production from carbohydrate compounds made by plants from water and carbon dioxide, were developed several decades ago. But these catalysts operate with ultraviolet light, which accounts for only 4% of the incoming solar energy and thus renders the overall process impractical. For this reason, considerable efforts have been invested in developing photocatalysts capable of using the less energetic but more abundant visible light, which accounts for about 43% of the incoming solar energy. However, systems that are sufficiently stable and efficient for practical use have not yet been realized. Here we show that doping of indium-tantalum-oxide with nickel yields a series of photocatalysts, In(1-x)Ni(x)TaO(4) (x = 0-0.2), which induces direct splitting of water into stoichiometric amounts of oxygen and hydrogen under visible light irradiation with a quantum yield of about 0.66%. Our findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for 'clean' hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.
2,931 citations
TL;DR: This communication presents the recent results that the activity of photocatalytic H2 production can be significantly enhanced when a small amount of MoS2 is loaded on CdS as cocatalyst.
Abstract: This communication presents our recent results that the activity of photocatalytic H2 production can be significantly enhanced when a small amount of MoS2 is loaded on CdS as cocatalyst. The MoS2/CdS catalysts show high rate of H2 evolution from photocatalytic re-forming of lactic acid under visible light irradiation. The rate of H2 evolution on CdS is increased by up to 36 times when loaded with only 0.2 wt % of MoS2, and the activity of MoS2/CdS is even higher than those of the CdS photocatalysts loaded with different noble metals, such as Pt, Ru, Rh, Pd, and Au. The junction formed between MoS2 and CdS and the excellent H2 activation property of MoS2 are supposed to be responsible for the enhanced photocatalytic activity of MoS2/CdS.
1,733 citations
TL;DR: In this paper, the state-of-the-art progress of semiconductor/semiconductor heterostructured photocatalysts with diverse models, including type-I and type-II heterojunctions, Z-scheme system, p-n heterojunction, and homojunction band alignments, were explored for effective improvement of photocatalysis activity through increase of the visible-light absorption, promotion of separation, and transportation of the photoinduced charge carries.
Abstract: Semiconductor photocatalysts have received much attention in recent years due to their great potentials for the development of renewable energy technologies, as well as for environmental protection and remediation. The effective harvesting of solar energy and suppression of charge carrier recombination are two key aspects in photocatalysis. The formation of heterostructured photocatalysts is a promising strategy to improve photocatalytic activity, which is superior to that of their single component photocatalysts. This Feature Article concisely summarizes and highlights the state-of-the-art progress of semiconductor/semiconductor heterostructured photocatalysts with diverse models, including type-I and type-II heterojunctions, Z-scheme system, p–n heterojunctions, and homojunction band alignments, which were explored for effective improvement of photocatalytic activity through increase of the visible-light absorption, promotion of separation, and transportation of the photoinduced charge carries, and enhancement of the photocatalytic stability.
680 citations