Showing papers by "Wuhan University of Technology published in 2018"
TL;DR: In this article, a review summarizes the recent significant progress on the design of g-C3N4-based heterostructured photocatalysts and their special separation/transfer mechanisms of photogenerated charge carriers.
Abstract: Photocatalysis is considered as one of the promising routes to solve the energy and environmental crises by utilizing solar energy. Graphitic carbon nitride (g-C3N4) has attracted worldwide attention due to its visible-light activity, facile synthesis from low-cost materials, chemical stability, and unique layered structure. However, the pure g-C3N4 photocatalyst still suffers from its low separation efficiency of photogenerated charge carriers, which results in unsatisfactory photocatalytic activity. Recently, g-C3N4-based heterostructures have become research hotspots for their greatly enhanced charge carrier separation efficiency and photocatalytic performance. According to the different transfer mechanisms of photogenerated charge carriers between g-C3N4 and the coupled components, the g-C3N4-based heterostructured photocatalysts can be divided into the following categories: g-C3N4-based conventional type II heterojunction, g-C3N4-based Z-scheme heterojunction, g-C3N4-based p–n heterojunction, g-C3N4/metal heterostructure, and g-C3N4/carbon heterostructure. This review summarizes the recent significant progress on the design of g-C3N4-based heterostructured photocatalysts and their special separation/transfer mechanisms of photogenerated charge carriers. Moreover, their applications in environmental and energy fields, e.g., water splitting, carbon dioxide reduction, and degradation of pollutants, are also reviewed. Finally, some concluding remarks and perspectives on the challenges and opportunities for exploring advanced g-C3N4-based heterostructured photocatalysts are presented.
1,759 citations
1,107 citations
TL;DR: In this article, a review concisely compiles the recent progress in the fabrication, modification, and major applications of the direct Z-scheme photocatalysts; the latter include water splitting, carbon dioxide reduction, degradation of pollutants, and biohazard disinfection.
1,013 citations
TL;DR: The results suggest that the H2 O-solvated Zn2+ possesses largely reduced effective charge and thus reduced electrostatic interactions with the V2 O5 framework, effectively promoting its diffusion.
Abstract: Low-cost, environment-friendly aqueous Zn batteries have great potential for large-scale energy storage, but the intercalation of zinc ions in the cathode materials is challenging and complex. Herein, the critical role of structural H2O on Zn2+ intercalation into bilayer V2O5·nH2O is demonstrated. The results suggest that the H2O-solvated Zn2+ possesses largely reduced effective charge and thus reduced electrostatic interactions with the V2O5 framework, effectively promoting its diffusion. Benefited from the “lubricating” effect, the aqueous Zn battery shows a specific energy of ≈144 Wh kg−1 at 0.3 A g−1. Meanwhile, it can maintain an energy density of 90 Wh kg−1 at a high power density of 6.4 kW kg−1 (based on the cathode and 200% Zn anode), making it a promising candidate for high-performance, low-cost, safe, and environment-friendly energy-storage devices.
987 citations
TL;DR: This work reports a new metal-free phosphorene/g-C3 N4 photocatalyst and sheds lights on the design and fabrication of 2D/2D VDW heterojunction for applications in catalysis, electronics, and optoelectronics.
Abstract: The generation of green hydrogen (H2 ) energy using sunlight is of great significance to solve the worldwide energy and environmental issues. Particularly, photocatalytic H2 production is a highly promising strategy for solar-to-H2 conversion. Recently, various heterostructured photocatalysts with high efficiency and good stability have been fabricated. Among them, 2D/2D van der Waals (VDW) heterojunctions have received tremendous attention, since this architecture can promote the interfacial charge separation and transfer and provide massive reactive centers. On the other hand, currently, most photocatalysts are composed of metal elements with high cost, limited reserves, and hazardous environmental impact. Hence, the development of metal-free photocatalysts is desirable. Here, a novel 2D/2D VDW heterostructure of metal-free phosphorene/graphitic carbon nitride (g-C3 N4 ) is fabricated. The phosphorene/g-C3 N4 nanocomposite shows an enhanced visible-light photocatalytic H2 production activity of 571 µmol h-1 g-1 in 18 v% lactic acid aqueous solution. This improved performance arises from the intimate electronic coupling at the 2D/2D interface, corroborated by the advanced characterizations techniques, e.g., synchrotron-based X-ray absorption near-edge structure, and theoretical calculations. This work not only reports a new metal-free phosphorene/g-C3 N4 photocatalyst but also sheds lights on the design and fabrication of 2D/2D VDW heterojunction for applications in catalysis, electronics, and optoelectronics.
683 citations
TL;DR: In this article, an advanced Co-Nx/C nanorod array derived from 3D ZIF nanocrystals with superior electrocatalytic activity and stability toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) compared to commercial Pt/C and IrO2, respectively, is synthesized.
Abstract: Designing a highly active electrocatalyst with optimal stability at low cost is must and non-negotiable if large-scale implementations of fuel cells are to be fully realized. Zeolitic-imidazolate frameworks (ZIFs) offer rich platforms to design multifunctional materials due to their flexibility and ultrahigh surface area. Herein, an advanced Co–Nx/C nanorod array derived from 3D ZIF nanocrystals with superior electrocatalytic activity and stability toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) compared to commercial Pt/C and IrO2, respectively, is synthesized. Remarkably, as a bifunctional catalyst (Ej = 10 (OER) − E1/2 (ORR) ≈ 0.65 V), it further displays high performance of Zn–air batteries with high cycling stability even at a high current density. Such supercatalytic properties are largely attributed to the synergistic effect of the chemical composition, high surface area, and abundant active sites of the nanorods. The activity origin is clarified through post oxygen reduction X-ray photoelectron spectroscopy analysis and density functional theory studies. Undoubtedly, this approach opens a new avenue to strategically design highly active and performance-oriented electrocatalytic materials for wider electrochemical energy applications.
682 citations
TL;DR: In this article, the authors proposed to use aqueous electrolyte to replace the organic electrolyte for reducing the cost and environmental pollution, and showed that it is difficult to find suitable cathode material as the host for the intercalation of Zn2+ owing to the high polarization of ZN2+ as well as the narrow applicable voltage range.
Abstract: DOI: 10.1002/aenm.201702463 other secondary batteries.[6–8] However, LIBs are too expensive to scale up for the processing cost resulted from the limited lithium resources, and SIBs are subjected to complicated issues of safety as well as environmental issues.[9–12] So, it is an urgent challenge for exploring new energy storage systems. As an alternative, rechargeable aqueous Zn-ion batteries (ZIBs) have received incremental attention owing to the following advantages, including low cost, safety, and environmentally friendly.[13] Meanwhile, using aqueous electrolyte to replace the organic electrolyte is of great significance for reducing the cost and environmental pollution.[14] However, it is difficult to find suitable cathode material as the host for the intercalation of Zn2+ owing to the high polarization of Zn2+ as well as the narrow applicable voltage range, which is limited by the water splitting in the aqueous battery system.[15] Typically, polymorphs of MnO2 (α-, γ-phase) are highly attractive as the cathode material because of the tunnel structure suiting for the intercalation of Zn2+ and a matched potential within the stable range of water. Some results, based on the reversible intercalation of Zn2+, have been reported in recent years, and they show either limited specific capacity or poor cycling performance.[16–19] Recently, the MnO2 nanofiber electrode, reported by Liu and co-workers, shows high capacity and excellent cycling performance.[20] However, the rate performance is not high enough due to the sluggish reaction dynamics of conversion reaction. Prussian blue analogues, including of zinc hexacyanoferrate and copper hexacyanoferrate, are another class of cathode materials, which show limited specific capacity as well as poor cyclic stability.[21–23] Until very recently, vanadiumbased materials are explored for reversible Zn2+ intercalation.[24] Nazar and co-workers reported a bilayered Zn0.25V2O5·nH2O cathode, which shows a high-capacity and long-life performance.[25] However, the development of ZIBs is in the primary stage, some new cathode materials should also be explored to enhance the energy density as well as cycle life for ZIBs. Over the past decades, layered vanadium oxides have been applied as electrode materials for LIBs or SIBs due to their low cost and high capacities.[26,27] Generally, the bulk vanadium oxides suffer from a rapid capacity fading resulting from low electronic conductivity, poor structural stability during the ion de/intercalation.[28] Recent studies show that interlayer metal ions (MxVnOm, M = metal ion) can act as pillars to increase the Aqueous Zn-ion batteries (ZIBs) have received incremental attention because of their cost-effectiveness and the materials abundance. They are a promising choice for large-scale energy storage applications. However, developing suitable cathode materials for ZIBs remains a great challenge. In this work, pioneering work on the designing and construction of aqueous Zn//Na0.33V2O5 batteries is reported. The Na0.33V2O5 (NVO) electrode delivers a high capacity of 367.1 mA h g−1 at 0.1 A g−1, and exhibits long-term cyclic stability with a capacity retention over 93% for 1000 cycles. The improvement of electrical conductivity, resulting from the intercalation of sodium ions between the [V4O12]n layers, is demonstrated by single nanowire device. Furthermore, the reversible intercalation reaction mechanism is confirmed by X-ray diffraction, Raman, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy analysis. The outstanding performance can be attributed to the stable layered structure and high conductivity of NVO. This work also indicates that layered structural materials show great potential as the cathode of ZIBs, and the indigenous ions can act as pillars to stabilize the layered structure, thereby ensuring an enhanced cycling stability. Zinc Ion Batteries
601 citations
TL;DR: Benefiting from structure functionalities and electronic control of a single-atom iron active center, the catalyst shows a remarkable performance with enhanced kinetics and activity for oxygen reduction in both alkaline and acid media and shows promise for substitution of expensive platinum to drive the cathodic oxygen reduction reaction in zinc-air batteries and hydrogen-air fuel cells.
Abstract: Efficient, durable and inexpensive electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics and achieve high-performance are highly desirable. Here we develop a strategy to fabricate a catalyst comprised of single iron atomic sites supported on a nitrogen, phosphorus and sulfur co-doped hollow carbon polyhedron from a metal-organic framework@polymer composite. The polymer-based coating facilitates the construction of a hollow structure via the Kirkendall effect and electronic modulation of an active metal center by long-range interaction with sulfur and phosphorus. Benefiting from structure functionalities and electronic control of a single-atom iron active center, the catalyst shows a remarkable performance with enhanced kinetics and activity for oxygen reduction in both alkaline and acid media. Moreover, the catalyst shows promise for substitution of expensive platinum to drive the cathodic oxygen reduction reaction in zinc-air batteries and hydrogen-air fuel cells.
596 citations
TL;DR: A two-step intercalation mechanism that Zn ions first insert into the layers and then the tunnels of MnO2 framework is proved by in situ X-ray diffraction, galvanostatic intermittent titration technique, andX-ray photoelectron spectroscopy characterizations.
Abstract: The development of manganese dioxide as the cathode for aqueous Zn-ion battery (ZIB) is limited by the rapid capacity fading and material dissolution. Here, a highly reversible aqueous ZIB using graphene scroll-coated α-MnO2 as the cathode is proposed. The graphene scroll is uniformly coated on the MnO2 nanowire with an average width of 5 nm, which increases the electrical conductivity of the MnO2 nanowire and relieves the dissolution of the cathode material during cycling. An energy density of 406.6 Wh kg-1 (382.2 mA h g-1 ) at 0.3 A g-1 can be reached, which is the highest specific energy value among all the cathode materials for aqueous Zn-ion battery so far, and good long-term cycling stability with 94% capacity retention after 3000 cycles at 3 A g-1 are achieved. Meanwhile, a two-step intercalation mechanism that Zn ions first insert into the layers and then the tunnels of MnO2 framework is proved by in situ X-ray diffraction, galvanostatic intermittent titration technique, and X-ray photoelectron spectroscopy characterizations. The graphene scroll-coated metallic oxide strategy can also bring intensive interests for other energy storage systems.
569 citations
TL;DR: In this paper, a rice crust-like structure was achieved through the uniform distribution of TiO2 nanoparticles on MXene Ti3C2 through calcination method and a unique rice crustlike structure of the prepared samples rendered the composite with large population of the surface active sites.
557 citations
TL;DR: In this paper, the state-of-the-art engineering of efficient photocatalysts for dinitrogen (N2) fixation toward NH3 synthesis is reviewed and the challenges, outlooks and future prospects at the forefront of this research platform are presented.
Abstract: The burgeoning development of ammonia (NH3) synthesis technology addresses the urgency of food intake required to sustain the population growth of the last 100 years. To date, NH3 has mostly been synthesized by the Haber–Bosch process in industry. Under the ever-increasing pressure of the fossil fuel depletion crisis and anthropogenic global climate change with continuous CO2 emission in the 21st century, research targeting the synthesis of NH3 under mild conditions in a sustainable and environment friendly manner is vigorous and thriving. Therefore, the focus of this review is the state-of-the-art engineering of efficient photocatalysts for dinitrogen (N2) fixation toward NH3 synthesis. Strenuous efforts have been devoted to modifying the intrinsic properties of semiconductors (i.e. poor electron transport, rapid electron–hole recombination and sluggish reaction kinetics), including nanoarchitecture design, crystal facet engineering, doping and heterostructuring. Herein, this review provides insights into the most recent advancements in understanding the charge carrier kinetics of photocatalysts with respect to charge transfer, migration and separation, which are of fundamental significance to photocatalytic N2 fixation. Subsequently, the challenges, outlooks and future prospects at the forefront of this research platform are presented. As such, it is anticipated that this review will shed new light on photocatalytic N2 fixation and NH3 synthesis and will also provide a blueprint for further investigations and momentous breakthroughs in next-generation catalyst design.
TL;DR: A universal potassium passivation strategy is developed to improve the quality of slot-die printed tin oxide electron transport layers and demonstrate highly efficient and hysteresis-free flexible devices.
Abstract: Perovskite solar cells (PSCs) have reached an impressive efficiency over 23%. One of its promising characteristics is the low-cost solution printability, especially for flexible solar cells. However, printing large area uniform electron transport layers on rough and soft plastic substrates without hysteresis is still a great challenge. Herein, we demonstrate slot-die printed high quality tin oxide films for high efficiency flexible PSCs. The inherent hysteresis induced by the tin oxide layer is suppressed using a universal potassium interfacial passivation strategy regardless of fabricating methods. Results show that the potassium cations, not the anions, facilitate the growth of perovskite grains, passivate the interface, and contribute to the enhanced efficiency and stability. The small size flexible PSCs achieve a high efficiency of 17.18% and large size (5 × 6 cm2) flexible modules obtain an efficiency over 15%. This passivation strategy has shown great promise for pursuing high performance large area flexible PSCs.
TL;DR: A single-nanowire-based zinc-ion battery is assembled, which reveals the intrinsic Zn2+ storage mechanism at nanoscale and makes Na2V6O16·1.63H2O a promising cathode for a low-cost and safe aqueous zinc-ION battery.
Abstract: Rechargeable aqueous zinc-ion batteries are highly desirable for grid-scale applications due to their low cost and high safety; however, the poor cycling stability hinders their widespread application Herein, a highly durable zinc-ion battery system with a Na2V6O16·163H2O nanowire cathode and an aqueous Zn(CF3SO3)2 electrolyte has been developed The Na2V6O16·163H2O nanowires deliver a high specific capacity of 352 mAh g–1 at 50 mA g–1 and exhibit a capacity retention of 90% over 6000 cycles at 5000 mA g–1, which represents the best cycling performance compared with all previous reports In contrast, the NaV3O8 nanowires maintain only 17% of the initial capacity after 4000 cycles at 5000 mA g–1 A single-nanowire-based zinc-ion battery is assembled, which reveals the intrinsic Zn2+ storage mechanism at nanoscale The remarkable electrochemical performance especially the long-term cycling stability makes Na2V6O16·163H2O a promising cathode for a low-cost and safe aqueous zinc-ion battery
TL;DR: In this article, a 2D/2D g-C3N4/MnO2 heterostructured photocatalyst was synthesized via in situ growth of MnO2 nanosheets on the surface of G-C 3N4 nanolayers using a wet-chemical method.
Abstract: Constructing two-dimensional (2D) composites using layered materials is considered to be an effective approach to achieve high-efficiency photocatalysts. Herein, a 2D/2D g-C3N4/MnO2 heterostructured photocatalyst was synthesized via in situ growth of MnO2 nanosheets on the surface of g-C3N4 nanolayers using a wet-chemical method. The hybrid nanomaterial was characterized by a range of techniques to study its micromorphology, structure, chemical composition/states, and so on. The g-C3N4/MnO2 nanocomposite exhibited greatly improved photocatalytic activities for dye degradation and phenol removal in comparison to the single g-C3N4 or MnO2 component. On the basis of the electron paramagnetic resonance spectra, X-ray photoelectron spectra, and the Mott–Schottky measurements, we consider that a Z-scheme heterojunction was generated between the g-C3N4 nanosheets and MnO2 nanosheets, wherein the photoinduced electrons in MnO2 combined with the holes in g-C3N4, leading to enhanced charge carrier extraction and ut...
TL;DR: In this article, an approach that improves the stability of non-flammable phosphate electrolytes by adjusting the molar ratio of Li salt to solvent was proposed. But their compatibility with electrode materials, especially graphite anodes, remains an obstacle owing to the strong catalytic activity of the anode surfaces.
Abstract: Non-flammable electrolytes could intrinsically eliminate fire hazards and improve battery safety, but their compatibility with electrode materials, especially graphite anodes, remains an obstacle owing to the strong catalytic activity of the anode surfaces. Here, we report an approach that improves the stability of non-flammable phosphate electrolytes by adjusting the molar ratio of Li salt to solvent. At a high Li salt-to-solvent molar ratio (~1:2), the phosphate solvent molecules are mostly coordinated with the Li+ cations, and the undesired reactivity of the solvent molecules toward the graphite anode can be effectively suppressed. High cycling Coulombic efficiency (99.7%), good cycle life and safe operation of commercial 18650 Li-ion cells with these electrolytes are demonstrated. In addition, these non-flammable electrolytes show reduced reactivity toward Li-metal electrodes. Non-dendritic Li-metal plating and stripping in Li–Cu half-cells are demonstrated with high Coulombic efficiency (>99%) and good stability.
TL;DR: In this paper, a ternary Ag2CrO4/g-C3N4/GO composite photocatalyst was fabricated for photocatalytic CO2 reduction into methanol (CH3OH) and methane (CH4).
Abstract: Graphitic carbon nitride (g-C3N4)-based photocatalysts holds great promise on photocatalytic CO2 conversion into solar fules; however, the efficiency of pristine g-C3N4 is currently limited by its poor visible light absorption and rapid charge recombination. Employing silver chromate (Ag2CrO4) nanoparticles as photosensitizer and graphene oxide (GO) as cocatalyst, a novel ternary Ag2CrO4/g-C3N4/GO composite photocatalyst was fabricated for photocatalytic CO2 reduction into methanol (CH3OH) and methane (CH4). The ternary composites exhibited an enhanced CO2 conversion activity with a turnover frequency of 0.30 h–1, which was 2.3 times that of pristine g-C3N4 under simulated sunlight irradiation. The enhanced photocatalytic activity was due to broadened light absorption, higher CO2 adsorption and more efficient charge separation. Specifically, due to the matched band structure and appropriate loading ratio of Ag2CrO4, a direct Z-scheme Ag2CrO4/g-C3N4 heterojunction is formed, driven by the internal electric field across the Ag2CrO4/g-C3N4 interface. The formation of the direct Z-scheme heterojunction is substantiated by radical scavenging experiments and density functional theory calculations, and it benefits the photocatalytic reaction by accelerating the charge separation and improving the redox ability. Furthermore, GO cocatalyst not only promotes the charge transfer but also provides plentiful CO2 adsorption and catalytic sites. This work exemplifies the facile development of ternary g-C3N4-based photocatalysts with high CO2-conversion activity by coupling a small amount of Ag-based photosensitizer and metal-free cocatalyst.
TL;DR: In this paper, the zinc anode protection in neutral or mild acidic aqueous electrolytes has been investigated, but to date, there are few reports concerning the zinc protection.
Abstract: DOI: 10.1002/admi.201800848 electrolyte-based batteries can provide structural robustness and cost advantages over competing lithium-ion batteries. Among those aqueous batteries, zinc metal batteries with zinc as anode including zinc-air battery and Zn–MnO2 battery has been investigated intensively due to its high theoretical capacity (820 mAh g−1), low negative potential (−0.762 V vs SHE), abundance, low toxicity, and the intrinsic safety advantages.[18–30] In this regard, aqueous zinc ion batteries are expected to make substantial impacts toward advanced energy storage technologies, especially in stationary grid storage. Despite the current success in exploration of cathode (including air cathode, MnO2, and so on),[20,21,23,31–35] an important barrier of the Zn-based batteries is the poor cycle life, which mainly derives from the drawbacks of the Zn metal anode and the electrolyte. The zinc corrosion behavior in the alkaline electrolyte has been studied long time ago. Several successful strategies have been adopted to address the issue through the use of soluble additives in the alkaline electrolyte,[36] the redesign of zinc anode into three dimensional zinc foam[37] and so on. However, to date, there are few reports concerning the zinc anode protection in neutral or mild acidic aqueous electrolytes. Compared with the alkaline electrolyte where the charge carrier is Zn(OH)4
TL;DR: A novel concept of edge computing for mobile blockchain and an economic approach for edge computing resource management are introduced and a prototype of mobile edge computing enabled blockchain systems are presented with experimental results to justify the proposed concept.
Abstract: Blockchain, as the backbone technology of the current popular Bitcoin digital currency, has become a promising decentralized data management framework. Although blockchain has been widely adopted in many applications (e.g., finance, healthcare, and logistics), its application in mobile services is still limited. This is due to the fact that blockchain users need to solve preset proof-of-work puzzles to add new data (i.e., a block) to the blockchain. Solving the proof of work, however, consumes substantial resources in terms of CPU time and energy, which is not suitable for resource-limited mobile devices. To facilitate blockchain applications in future mobile Internet of Things systems, multiple access mobile edge computing appears to be an auspicious solution to solve the proof-of-work puzzles for mobile users. We first introduce a novel concept of edge computing for mobile blockchain. Then we introduce an economic approach for edge computing resource management. Moreover, a prototype of mobile edge computing enabled blockchain systems is presented with experimental results to justify the proposed concept.
TL;DR: In this article, a review summarizes the recent efforts on electrode materials with hierarchical structures, and discusses the effects of hierarchical structures on electrochemical performance in detail, including micro/nano and hetero/hierarchical structures characterized by ordered assembly of different sizes, phases, and/or pores.
Abstract: Since their successful commercialization in 1990s, lithium-ion batteries (LIBs) have been widely applied in portable digital products. The energy density and power density of LIBs are inadequate, however, to satisfy the continuous growth in demand. Considering the cost distribution in battery system, it is essential to explore cathode/anode materials with excellent rate capability and long cycle life. Nanometer-sized electrode materials could quickly take up and store numerous Li+ ions, afforded by short diffusion channels and large surface area. Unfortunately, low thermodynamic stability of nanoparticles results in electrochemical agglomeration and raises the risk of side reactions on electrolyte. Thus, micro/nano and hetero/hierarchical structures, characterized by ordered assembly of different sizes, phases, and/or pores, have been developed, which enable us to effectively improve the utilization, reaction kinetics, and structural stability of electrode materials. This review summarizes the recent efforts on electrode materials with hierarchical structures, and discusses the effects of hierarchical structures on electrochemical performance in detail. Multidimensional self-assembled structures can achieve integration of the advantages of materials with different sizes. Core/yolk-shell structures provide synergistic effects between the shell and the core/yolk. Porous structures with macro-, meso-, and micropores can accommodate volume expansion and facilitate electrolyte infiltration.
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.
01 Mar 2018
TL;DR: DFT calculations demonstrated that the coupling of Co-Nx active sites with B atoms prefers to adsorb an O2 molecule in side-on mode and accelerates ORR kinetics, which shows superior performance with an open-circuit potential of ∼1.4 V, a peak power density of ∼100.4 mW cm-2, and excellent durability.
Abstract: Structural and compositional engineering of atomic-scaled metal−N−C catalysts is important yet challenging in boosting their performance for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Here, boron (B)-doped Co−N−C active sites confined in hierarchical porous carbon sheets (denoted as Co-N,B-CSs) were obtained by a soft template self-assembly pyrolysis method. Significantly, the introduced B element gives an electron-deficient site that can activate the electron transfer around the Co−N−C sites, strengthen the interaction with oxygenated species, and thus accelerate reaction kinetics in the 4e− processed ORR and OER. As a result, the catalyst showed Pt-like ORR performance with a half-wave potential (E1/2) of 0.83 V versus (vs) RHE, a limiting current density of about 5.66 mA cm−2, and higher durability (almost no decay after 5000 cycles) than Pt/C catalysts. Moreover, a rechargeable Zn–air battery device comprising this Co-N,B-CSs catalyst shows superior performance with an op...
TL;DR: In this article, the authors compare liquid-and solid-state batteries and emphasize the challenges in solid-solid interfaces, including interphase formation, cathode-electrolyte interface, anode-electriclyte interfaces, and interparticle interface.
TL;DR: In this paper, a novel hybrid TiO2 nanofiber coated by CuInS2 nanoplates through a hydrothermal method was fabricated for CO2 reduction under irradiation.
Abstract: Photocatalytic CO2 reduction into solar fuels over photocatalysts has theoretically and practically become a hot research topic. Herein, we fabricated a novel hybrid TiO2 nanofiber coated by CuInS2 nanoplates through a hydrothermal method. The materials were characterized by X-ray diffraction, electron microscopes, UV–vis absorption spectra, nitrogen sorption, X-ray photoelectron spectroscopy and electrochemical impudence spectroscopy. The resulting TiO2/CuInS2 hybrid nanofibers exhibit superior photocatalytic activity for CO2 reduction under irradiation, due to the generation of direct Z-scheme heterojunction between TiO2 and CuInS2. This work may provide an alternate methodology to design and fabricate multicomponent TiO2-based photocatalyst for high-efficiency CO2 photoreduction.
TL;DR: The unique hierarchical Co3 O4 /NHCS core-shell structure with hierarchical structures is a promising electrode material for high-performance supercapacitors.
Abstract: Co3 O4 /nitrogen-doped carbon hollow spheres (Co3 O4 /NHCSs) with hierarchical structures are synthesized by virtue of a hydrothermal method and subsequent calcination treatment. NHCSs, as a hard template, can aid the generation of Co3 O4 nanosheets on its surface; while SiO2 spheres, as a sacrificed-template, can be dissolved in the process. The prepared Co3 O4 /NHCS composites are investigated as the electrode active material. This composite exhibits an enhanced performance than Co3 O4 itself. A higher specific capacitance of 581 F g-1 at 1 A g-1 and a higher rate performance of 91.6% retention at 20 A g-1 are achieved, better than Co3 O4 nanorods (318 F g-1 at 1 A g-1 and 67.1% retention at 20 A g-1 ). In addition, the composite is employed as a positive electrode to fabricate an asymmetric supercapacitor. The device can deliver a high energy density of 34.5 Wh kg-1 at the power density of 753 W kg-1 and display a desirable cycling stability. All of these attractive results make the unique hierarchical Co3 O4 /NHCS core-shell structure a promising electrode material for high-performance supercapacitors.
TL;DR: The increased density of states at the conduction band (CB) minimum in the monolayer BiO2-x is responsible for the enhanced photon response and photo-absorption, which were confirmed by UV/Vis-NIR diffuse reflectance spectra (DRS) and photocurrent measurements.
Abstract: Vacancy-rich layered materials with good electron transfer property are of great interesting. Herein, full spectrum responsive vacancy-rich monolayer BiO2-x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO2-x are responsible for the enhanced photon responsibility and photo-absorption, which was confirmed by UV-vis-NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO2-x, monolayer BiO2-x exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible and near-infrared light (NIR) irradiation attributed to the vacancy associates VBi-O‴ as confirmed by the positron annihilation spectra. The presence of VBi-O‴ defects in monolayer BiO2-x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient ultraviolet (UV), visible and NIR light responsive photocatalysts.
TL;DR: In this article, an Fe, Cu-coordinated ZIF-derived carbon framework (Cu@Fe-N-C) with a well-defined morphology of truncated rhombic dodecahedron is facilely prepared by introducing Fe2+ and Cu2+ during the growth of ZIF8, followed by pyrolysis.
Abstract: Zeolitic imidazole frameworks (ZIFs) offer rich platforms for rational design and construction of high-performance nonprecious-metal oxygen reduction reaction (ORR) catalysts owing to their flexibility, hierarchical porous structures, and high surface area. Herein, an Fe, Cu-coordinated ZIF-derived carbon framework (Cu@Fe-N-C) with a well-defined morphology of truncated rhombic dodecahedron is facilely prepared by introducing Fe2+ and Cu2+ during the growth of ZIF-8, followed by pyrolysis. The obtained Cu@Fe-N-C, with bimetallic active sites, large surface area, high nitrogen doping level, and conductive carbon frameworks, exhibits excellent ORR performance. It displays 50 mV higher half-wave potential (0.892 V) than that of Pt catalysts in an alkaline medium and comparable performance to Pt catalysts in an acidic medium. In addition, it also has excellent durability and methanol resistance ability in both acidic and alkaline solutions, which makes it one of the best Pt-free catalysts reported to date for ORR. Impressively, when being employed as a cathode catalyst in zinc–air batteries, Cu@Fe-N-C presents a higher peak power density of 92 mW cm−2 than that of Pt/C (74 mW cm−2) as well as excellent durability.