Short Diffusion Length Research Articles

Shape selectivity in linear paraffins hydroconversion in 10-membered-ring pore zeolites

Pd/zeolite-catalyzed hydroconversion of n-hexadecane (n-C16) and n-heptane (n-C7) was studied for 10MR (ZSM-5, ZSM-22), 12MR (ZSM-12), and EMM-23 (21MR × 10MR) zeolites. The catalytic activity depended on the Brønsted acidity and the crystalline domain size. n-C16 hydroconversion benefited from short diffusion lengths in ZSM-5 nanosheets compared to bulk ZSM-5. In general, over-cracking is dominant in ZSM-5 with a cracked product distribution skewed to C4 products, to be explained by a snug fit of particular dibranched isomers at zeolite intersections. This effect is less pronounced for the 1D 10MR pores in ZSM-22, which lacks intersections. Although large pores in ZSM-12 offer relatively high activity, those in EMM-23 do not. Based on selectivity patterns, EMM-23 behaves like ZSM-5, probably because of the trilobe shape of its 21MR pores acting as 10MR pores. Only ZSM-12 offers operation in the ideal hydrocracking regime, in the sense of impediments neither by hydrogenation nor by diffusion. Faster intrazeolite diffusion of n-C7 in comparison to n-C16 leads to a higher yield of isomers for the nanostructured zeolites. Overall, the hydroconversion of the smaller alkane is more substantially impacted by variations in the crystalline zeolite domain size.

Molten-based defect engineering polymeric carbon nitride quantum dots with enhanced hole extraction: An efficient photoelectrochemical cell for water oxidation

Polymeric carbon nitride (g-C3N4) has emerged as a promising material for energy-related applications. However, the utilization of g-C3N4 in photoelectrochemical cells is still limited by poor exciton mobility, sluggish hole extraction, and short electron diffusion length. Here, we report a molten-based defect engineering strategy to prepare nitrogen-deficient g-C3N4 quantum dots (SxCNQD) for photoelectrochemical water splitting. This novel strategy requires no chemical etching or secondary treatments like recent state-of-the-art defect introduction methods, and for the first time achieves the in-situ integration of nitrogen-vacancy defects (NVs) during the polymerization of g-C3N4. Theoretical evaluation and experimental validation identified that the involved structural NVs redistribute the electrons on the delocalized π-conjugated networks of g-C3N4 and creates an additional sub-band on the optical bandgap, which can effectively improve carrier separation, facilitate charge transport dynamics, and boost hole extraction. Beneficial from its featured topological structures and electronic properties, the S600CNQD@ZnO photoanode exhibits a markedly high photocurrent density of 193.8 μA cm−2 at 1.23 V vs. RHE, long-term durability, as well as an impressive IPCE value in an alkaline solution in the absence of sacrificial agent under visible light illumination.

Long-range exciton diffusion in molecular non-fullerene acceptors

The short exciton diffusion length associated with most classical organic semiconductors used in organic photovoltaics (5-20 nm) imposes severe limits on the maximum size of the donor and acceptor domains within the photoactive layer of the cell. Identifying materials that are able to transport excitons over longer distances can help advancing our understanding and lead to solar cells with higher efficiency. Here, we measure the exciton diffusion length in a wide range of nonfullerene acceptor molecules using two different experimental techniques based on photocurrent and ultrafast spectroscopy measurements. The acceptors exhibit balanced ambipolar charge transport and surprisingly long exciton diffusion lengths in the range of 20 to 47 nm. With the aid of quantum-chemical calculations, we are able to rationalize the exciton dynamics and draw basic chemical design rules, particularly on the importance of the end-group substituent on the crystal packing of nonfullerene acceptors.

Point and extended defects in heteroepitaxial β−Ga2O3 films

$\mathrm{G}{\mathrm{a}}_{2}{\mathrm{O}}_{3}$ is emerging as an excellent potential semiconductor for high power and optoelectronic devices. However, the successful development of $\mathrm{G}{\mathrm{a}}_{2}{\mathrm{O}}_{3}$ in a wide range of applications requires a full understanding of the role and nature of its point and extended defects. In this work, high quality epitaxial $\mathrm{G}{\mathrm{a}}_{2}{\mathrm{O}}_{3}$ films were grown on sapphire substrates by metal-organic chemical vapor deposition and fully characterized in terms of structural, optical, and electrical properties. Then defects in the films were investigated by a combination of depth-resolved Doppler broadening and lifetime of positron annihilation spectroscopies and thermally stimulated emission (TSE). Positron annihilation techniques can provide information about the nature and concentration of defects in the films, while TSE reveals the energy level of defects in the bandgap. Despite very good structural properties, the films exhibit short positron diffusion length, which is an indication of high defect density and long positron lifetime, a sign for the formation of Ga vacancy related defects and large vacancy clusters. These defects act as deep and shallow traps for charge carriers as revealed from TSE, which explains the reason behind the difficulty of developing conductive $\mathrm{G}{\mathrm{a}}_{2}{\mathrm{O}}_{3}$ films on non-native substrates. Positron lifetime measurements also show nonuniform distribution of vacancy clusters throughout the film depth. Further, the work investigates the modification of defect nature and properties through thermal treatment in various environments. It demonstrates the sensitivity of $\mathrm{G}{\mathrm{a}}_{2}{\mathrm{O}}_{3}$ microstructures to the growth and thermal treatment environments and the significant effect of modifying defect structure on the bandgap and optical and electrical properties of $\mathrm{G}{\mathrm{a}}_{2}{\mathrm{O}}_{3}$.

Photoelectrochemical water oxidation performance promoted by a cupric oxide-hematite heterojunction photoanode

Hematite is a promising material for photoelectrochemical (PEC) water oxidation due to its narrow bandgap and chemical stability in alkaline electrolytes. However, the PEC performance of hematite is known to be inhibited by a short carrier diffusion length and slow kinetics for the oxygen evolution process. The rational control of morphology, crystallinity, and interfacial charge transfer plays an important role in tuning the PEC performance of α-Fe2O3 photoelectrodes. In this study, different iron oxide nano/microstructures are synthesized by the sintering of iron sheets in air at different temperatures. The synergetic effect of the surface morphology and crystallinity on the photocurrent and onset potential of the photoanode is investigated. The coral-like structure with high index (104) facets prepared at a high temperature shows a decreased onset potential, suggesting a strong correlation between the onset potential and crystalline orientation. To further improve the photocurrent density of this hematite photoanode, cupric oxide-hematite heterostructures are explored. An obvious improvement in the photocurrent density is observed from 1.1 to 1.6 V. The resulting α-Fe2O3/CuO photoanode exhibits a photocurrent density of 1.5 mA cm−2 at 1.6 V, 25% higher than that of the pristine hematite. The Mott-Schottky plot and EIS measurement indicate that the α-Fe2O3/CuO heterojunction facilitates the extraction of the accumulated holes in the hematite through a type-II band alignment and the CuO can serve as a catalyst for promoting the oxygen evolution reaction.

Effects of Thermal Diffusivity Analysis after Irradiation

The diffusion calculation gives a vivid understanding as to what happens in the SiC-cladded material. Molecular Dynamics (MD) and Molecular Statics are being employed to study the diffusion coefficient phenomena. The MD simulations in this study are been built on the ZBL potential. In this work we initially applied the MD simulation for minimization within the temperature range of 1000-3000 K. Then the MOX fuel is then used to perform assessment of radiation damage by ions at burnup temperatures as well. Various chemical states are developed depending on the condition of the fuel. Within the fuel lattice the O atoms break bonds with the U-Pu atoms at higher temperature. The very short diffusion lengths mechanisms results were obtained measured for uranium atom over the course of this 300ps simulation.

Interplay of adsorption, photo-absorption, electronic structure and charge carrier dynamics on visible light driven photocatalytic activity of Bi2MoO6/rGO (0D/2D) heterojunction

In the present research Bi2MoO6(BMO) QDs (0D) and reduce graphene oxide nanosheet (2D) (BMO/rGO)(0D/2D) heterojunction with different weight ratio of GO nanosheet were synthesized using facile method. XRD, UV–vis spectroscopy, XPS, FTIR, BET, PL, TRPL, TEM/HRTEM, ESR and photoelectrochemical (PEC) measurements were used for the characterization and understanding the enhancement effect on photoactivity of the synthesis photocatalyst. The BMO (0D) QDs provide more active sites and short diffusion length of photogenerated charges. Whereas, 2D rGO nanosheet presents complementary surface area to allow the formation of distinct heterojunction with majority of the 0D QDs by preventing agglomeration of particles and excellent conductivity. TEM images explicitly showed the uniform distribution of 0D BMO particles of size 8−10 nm over 2D rGO which lead to formation of distinct Schottky junction. These exclusive properties of 0D/2D heterojunction result in effective degradation of organic pollutants such as Rhodamine-B dye, p-nitrophenol a phenol group and acetaminophen a pharmaceuticals compound with 100 %, 94 % and 87 % in 180 min; and degradation rate achieved was 9.35, 8.60 and 7.53 as compared to 0D BMO QDs under simulated solar light irradiation. The scavenging experiments revealed that h+ and O2• - radicals are main reactive species involved in the photodegradation along with contribution from photogenerated e−. The increased photocatalytic efficiency is ascribed to enlarge solar light absorption, increased adsorption, increased surface area, conductivity with substantial contribution of photo-induced charge separation and transfer in BMO/rGO (0D/2D) heterojunction.

Boosting the Utilization and Electrochemical Performances of Polyaniline by Forming a Binder-Free Nanoscale Coaxially Coated Polyaniline/Carbon Nanotube/Carbon Fiber Paper Hierarchical 3D Microstructure Composite as a Supercapacitor Electrode.

Nanoscale polyaniline (PANI) is formed on a hierarchical 3D microstructure carbon nanotubes (CNTs)/carbon fiber paper (CFP) substrate via a one-step electrochemical polymerization method. The chemical and structural properties of the binder-free PANI/CNTs/CFP electrode are characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. The specific capacitance of PANI/CNTs/CFP tested in a symmetric two-electrode system reaches 731.6 mF·cm–2 (1354.7 F·g–1) at a current density of 1 mA·cm–2 (1.8 A·g–1). The symmetric supercapacitor device demonstrates excellent cycling performance up to 10,000 cycles with a capacitance retention of 81.4% at a current density of 1 mA·cm–2 (1.8 A·g–1). The results demonstrate that the binder-free CNTs/CFP composite is a strong backbone for depositing ultrathin PANI layers at a high mass loading. The hierarchical 3D microstructure PANI/CNTs/CFP provides enough space and transporting channels to form an efficient electrode–electrolyte interface for the supercapacitance reaction. The formed nanoscale PANI film coaxially coated on the sidewalls of CNTs enables efficient charge transfer and a shortened diffusion length. Hence, the utilization efficiency and electrochemical performances of PANI are significantly improved. The rational design strategy of a CNT-based binder-free hierarchical 3D microstructure can be used in preparing various advanced energy-storage electrodes for electrochemical energy-storage and conversion systems.

In situ synthesis and characterization of sulfonic acid functionalized hierarchical silica monoliths

Surface functionalization of porous materials with sulfonic acid (SO3H) groups is of particular interest in applications involving ion exchange, acidic catalysis and proton conduction. Macro-mesoporous silica monoliths are ideal support structures for these applications, as they combine advection-dominated mass transport in the macropores with short diffusion lengths and a large surface area (available for functionalization) in their mesoporous skeleton. Here, we report on SO3H functionalized sol–gel silica monoliths with bimodal pore systems exhibiting macro- and mesoporosity, prepared according to a simple, efficient in situ synthesis protocol. Based on the co-condensation approach, thiol groups were introduced homogeneously into the pore structure, followed by their oxidation to SO3H groups and the simultaneous removal of the template. The macropore size, specific surface area, and coverage with SO3H groups are easily adjusted in this synthesis route. Importantly, the hybrid monoliths have a substantially narrower mesopore size distribution (relative standard deviation ~25%) than conventional sol–gel materials (>40%) and can be engineered crack-free in a robust column design (suitable for high-pressure flow-through operation) with mean mesopore size down to ~7 nm. They are characterized by IR spectroscopy, thermogravimetry, and elemental analysis as well as 13C and 29Si solid state NMR to corroborate the simple, efficient combination of sol–gel-based material synthesis, surface functionalization, and template removal (i.e., polymer extraction). Complementary, inverse gas chromatography is presented as a new approach to characterize the incorporated SO3H groups via surface energy analysis and particularly resolve changes in the Lewis acid–base characteristics engendered by that functionalization.

Binder-assisted electrostatic spray deposition of LiCoO2 and graphite films on coplanar interdigitated electrodes for flexible/wearable lithium-ion batteries

Flexible battery technologies have lately attracted much attention in the field of wearable electronics. A coplanar interdigitated electrode design encompasses the merits of bending tolerance and increased kinetics owing to shortened diffusion length for applications in these batteries. However, the fabrication of a coplanar patterned electrode remains a challenge because the conventional slurry casting method is unsuitable. In this study, we present a new process to prepare an interdigitated coplanar electrode using binder-assisted electrostatic spray deposition (ESD) without vacuum or high-cost techniques. Using the binder-assisted ESD method, it is possible to deposit powder of any type or size. Moreover, this approach is versatile and universal for application to the design of any coplanar cell configuration and is achieved using a binder-assisted dispersion method based on a commercially available active material. A full-cell flexible battery is fabricated with a coplanar interdigitated electrode using a LiCoO2 cathode and graphite anode. The low cost, simplicity, efficacy, and flexibility of this method are very promising attributes in the design and fabrication of flexible/wearable batteries.

An Efficient Emulsion‐Induced Interface Assembly Approach for Rational Synthesis of Mesoporous Carbon Spheres with Versatile Architectures

AbstractMesoporous carbon matrix with open pore structure, short diffusion length, and large pore size can favor the in‐pore immobilization of active species and facilitate mass diffusion during catalytic reactions. However, a great difficulty still remains on controllable synthesis of uniform mesoporous carbon spheres with these structural characteristics. Herein, using amphiphilic Pluronic F127 as the surfactant, 1,3,5‐trimethyl benzene (TMB) as the pore swelling and interface‐adjusting agent, and dopamine as the carbon source, a robust emulsion‐induced interface assembly approach for rational synthesis of mesoporous carbon spheres is demonstrated. The interface assembly process, including dopamine polymerization and fusion of TMB/F127/dopamine emulsions, can be regulated by tuning the dosage of dopamine and ammonia water, resulting in mesoporous carbon spheres with tunable pore sizes and versatile architectures, such as vesicles, walnut shapes, spheres with dendritic‐like 3D radially aligned mesochannels (RA‐MC), and isolated spherical mesopores. Moreover, the derived RA‐MC is used as a promising matrix to immobilize ultra‐small Au nanoparticles (≈3 nm). The Au/RA‐MC exhibits no mass diffusion limitations in reduction of 4‐nitrophenol, showing high conversion efficiency and good recyclability. This work paves a new avenue for controllable synthesis of mesoporous carbon spheres with well‐developed mesoporosity and architectures and their application as novel heterogeneous catalysts.

Fabrication of Bilayer Fe<sub>2</sub>O<sub>3</sub>/ZnO Photoanode and its Photoelectrochemical Performance

Hematite (Fe2O3) is one of the abundant magnetic materials in nature. Hematite has good absorption ability in the region visible light and good electrochemical stability, which make this material is potential as photoanode for photoelectrochemical (PEC) cells. However, Fe2O3 has some disadvantages such as short hole diffusion length and low hole mobility. Therfore, it is necessarily to combine Fe2O3 with photocatalyst material to improve photoelectrochemical performances. ZnO is ones of photocatalist material with good electron mobility, wide band gaps, cheap and are easily fabricated. The aim of this study is to investigate the performance of bilayer Fe2O3/ZnO as photoanode for photoelectrochemical cell. The bilayer Fe2O3/ZnO was prepared by spin-coating techniques and doctor blade methods. The samples were characterized by X-ray diffarction, and Scanning Electron Microscopy. The performance of photoelectrochemical cell was investigated by Cyclic Voltammetry (CV) under light illumination. The result indicate that bilayer Fe2O3/ZnO has good photoelectrochemical properties.

A high-performance transparent photodetector via building hierarchical g-C3N4 nanosheets/CNTs van der Waals heterojunctions by a facile and scalable approach

Graphitic-carbon nitride (g-C3N4) as a novel two-dimensional (2D) material has attracted considerable attentions due to its unique properties and diverse applications. However, the poor electron-hole (e-h) separation efficiency and short carrier diffusion length greatly hinder its application in optoelectronic devices. Here, we present a solution-processed photodetector based on the g-C3N4 nanosheets and carbon nanotubes (CNTs). Through a layer by layer spin coating method, a grid-like active layer with a large number of g-C3N4 nanosheets/CNTs van der Waals heterojunctions can be assembled. This subtle structure endows the device an outstanding photoelectric conversion performance as well as a high transparency (72%). The photodetector exhibits a broadband response to UV and visible light. Under 365 nm UV illumination, a high responsivity up to 0.23 A/W has been obtained, which exceeds those of most current transparent photodetectors. This work not only presents the first transparent device based on g-C3N4, but also provides a paradigm on designing low-cost and high performance electronic devices with van der Waals heterojunctions.

Binder-free coaxially grown V6O13 nanobelts on carbon cloth as cathodes for highly reversible aqueous zinc ion batteries

For stable, high-capacity aqueous zinc ion batteries (AZIBs), layered metal oxides, especially with multivalent metal ions, are promising active materials (cathodes) with high operating voltages. However, when uses in batteries prepared with conventional electrode fabrication methods, these materials suffer from low electrical conductivity and high active material detachment from the current collector, leading to poor electrochemical performance. Here, we present the synthesis of ultrathin V6O13 nanobelts containing multiple valences (V4+ and V5+) grown coaxially on carbon cloth (CC) using a hydrothermal method for the first time. The ultrathin V6O13 integrated into CC shows advantages such as fast electron transfer between the active material and current collector, low active material detachment, and short diffusion length in metal ion insertion-extraction. In AZIBs, V6O13@CC displays promising reversible galvanostatic charge-discharge capacity retention during cycling with excellent rate capability. An initial specific capacity of 227 mAh g−1 is obtained at 9 A g−1 and nearly 99% is retained after 1000 cycles. This stable reversible capacity is attributed to enhanced electrical conductivity and low active material detachment from the current collector (carbon cloth). This report discusses the hydrothermal preparation of a flexible cathode on CC that is promising for high-performance aqueous metal ion batteries.

Oxidation of Polyunsaturated Lipid Membranes by Photocatalytic Titanium Dioxide Nanoparticles: Role of pH and Salinity.

In the present study, UV-induced membrane destabilization by TiO2 (anatase) nanoparticles was investigated by neutron reflectometry (NR), small-angle X-ray scattering (SAXS), quartz crystal microbalance with dissipation (QCM-D), dynamic light scattering (DLS), and ζ-potential measurements for phospholipid bilayers formed by zwitterionic palmitoyloleoylphosphatidylcholine (POPC) containing biologically relevant polyunsaturations. TiO2 nanoparticles displayed pH-dependent binding to such bilayers. Nanoparticle binding alone, however, has virtually no destabilizing effects on the lipid bilayers. In contrast, UV illumination in the presence of TiO2 nanoparticles activates membrane destabilization as a result of lipid oxidation caused by the generation of reactive oxygen species (ROS), primarily •OH radicals. Despite the short diffusion length characterizing these, the direct bilayer attachment of TiO2 nanoparticles was demonstrated to not be a sufficient criterion for an efficient UV-induced oxidation of bilayer lipids, the latter also depending on ROS generation in bulk solution. From SAXS and NR, minor structural changes were seen when TiO2 was added in the absence of UV exposure, or on UV exposure in the absence of TiO2 nanoparticles. In contrast, UV exposure in the presence of TiO2 nanoparticles caused large-scale structural transformations, especially at high ionic strength, including gradual bilayer thinning, lateral phase separation, increases in hydration, lipid removal, and potential solubilization into aggregates. Taken together, the results demonstrate that nanoparticle-membrane interactions ROS generation at different solution conditions act in concert to induce lipid membrane destabilization on UV exposure and that both of these need to be considered for understanding the performance of UV-triggered TiO2 nanoparticles in nanomedicine.

Robust, flexible and broadband photodetectors based on van der Waals graphene/C60 heterostructures

Low-dimensional carbon materials, such as conducting graphene, semiconducting C60 and their hybrids, have recently received a great deal of attention for the potential applications in low-cost flexible and wearable nanoelectronics, due to their remarkable mechanical, electrical and optoelectronic properties. While graphene exhibits intrinsically weak absorption and C60 is typically associated with low carrier mobility and short exciton diffusion length, the marriage of two materials is a synergetic route to overcome these technical short-comings. Here, we fabricate a van der Waals bonded graphene/C60 hybrid on a plastic substrate to demonstrate a highly sensitive flexible photodetector. Intimate electronic coupling across the all-carbon interface allows highly efficient interfacial charge transfer, which effectively dissociates the electron-hole pairs and leads to significant photoresponse across ultraviolet to near-infrared (∼104 A/W @ 405 nm). Thanks to remarkable absorption of C60, it enables the detection of weak signals including those from a lighter and fluorescent lighting. Simultaneously, the photodetector exhibits extraordinary mechanical flexibility, allowing excellent electric conductivity and stable light detection under quite large tensile strain. Furthermore, the flexible devices still exhibit a satisfactory photoresponse after 6 months, indicating the excellent environmental robustness. This scalable all-caron hybrids may provide a viable route to produce the high-performance flexible optoelectronic devices.

Accelerating lithium storage capability of cobalt sulfide encapsulated within anion dual-doped mesoporous carbon nanofibers

Metal sulfide materials are promising for the anodes of ultrafast lithium ion batteries (LIBs) for many potential high-technology devices because of their high electrical conductivity, high theoretical capacity, and chemical/electrochemical stability resulting from their unique crystal structures. Despite their significant advantages, these materials face an important challenge related to structural degradation, owing to the significant volume expansion of metal sulfide under ultrafast cycling conditions. This phenomenon leads to rapid capacity fading and must be improved for the practical application of ultrafast LIBs. In the present study, a unique architecture of cobalt sulfide encapsulated within anion dual (nitrogen and sulfur)-doped mesoporous carbon nanofibers (referred to as CoS-NS-PCNF) was fabricated via electrospinning and carbonization. The CoS-NS-PCNF exhibited superb ultrafast cycling performance including outstanding cycling stability (748.6 mAh g−1 with capacity retention of 96.5% at 100 mA g−1 after 100 cycles), a superb ultrafast cycling capacity (550.1 mAh g−1 at 2000 mA g−1), and excellent ultrafast cycling stability (514.6 mAh g−1 with capacity retention of 93.5% at 2000 mA g−1 after 500 cycles). Thus, the novel architecture has significant advantages for ultrafast lithium storage kinetics including a short lithium-ion diffusion length, a high ion/electron transfer rate, and effective prevention of volume expansion.

Remote Lightening and Ultrafast Transition: Intrinsic Modulation of Exciton Spatiotemporal Dynamics in Monolayer MoS2.

Devices operating with excitons have promising prospects for overcoming the dilemma of response time and integration in current generation of electron- or/and photon-based elements and devices. Although the intrinsic properties including edges, grain boundaries, and defects of atomically thin semiconductors have been demonstrated as a powerful tool to adjust the bandgap and exciton energy, investigating the intrinsic modulation of spatiotemporal dynamics still remains challenging on account of the short exciton diffusion length. Here, we achieve the attractive remote lightening phenomenon, in which the emission region could be far away (up to 14.6 μm) from the excitation center, by utilizing a femtosecond laser with ultrahigh peak power as excitation source and the edge region with high photoluminescence efficiency as a bright emitter. Furthermore, the ultrafast transition between exciton and trion is demonstrated, which provides insight into the intrinsic modulation on populations of exciton and trion states. The complete cascaded physical scenario of exciton spatiotemporal dynamics is eventually established. This work can refresh our perspective on the spatial nonuniformities of CVD-grown atomically thin semiconductors and provide important implications for developing durable and stable excitonic devices in the future.

Targeted Synthesis of Polymer and Microporous Carbon Nanofibers via Temperature‐Dependent and Molecularly‐Triggered Interfacial Assembly

AbstractMicroporous carbon nanofibers (CNFs) derived from polymer nanofibers (PNFs), featured with short radial diffusion length of ions, have been proposed as ideal electrode materials for energy storage devices. However, lacking precise control of selective formation of fibrous micelle templates, the targeted synthesis of microporous CNFs is still a challenge. To address this issue, PNFs are first fabricated by using triblock copolymer F127 as the structure directing agent via the temperature‐dependent and molecularly‐triggered interfacial assembly process. Two crucial factors are figured that determine the fibrous morphology of the assembled polymer. At suitable temperatures, F127 starts to form fibrous micelles, and molecular trigger hexamethylenetetramine generates formaldehyde and ammonia in situ. Then, phenolic polymer assemble around the fibrous micelles, following with the formation of PNFs. This feasible synthesis method can grow PNFs and precisely control the PNFs' diameters ranging from 30 to 80 nm. Microporous CNFs with high specific surface area of 1175 m2 g−1, and an average diameter of 40 nm can be prepared through carbonization of PNFs and an activation step. Taking such microporous CNFs as electrode materials for a supercapacitor, they exhibit an excellent specific capacitance 295 F g−1 at a high current density 50 A g−1.

Research Progress and Challenges ofα-Fe2O3 Photoanode for Photoelectrochemical Water Splitting

In recent years,photoelectrochemical(PEC)water splitting to produce hydrogen provides a clean and renewable pathway for future energy demands.hematite(α-Fe2O3)is a promising photoanode material owing to its narrow band gap(~2.1 eV),non-toxicity,natural abundance,and photo-stability.However,some drawbacks greatly limited the photoconversion efficiencies of Fe2O3-based photoanodes,such as poor electrical conductivity,short hole diffusion length(2~4 nm),sluggish surface oxygen evolution kinetics,and short excited-state lifetime(<10×10^-12 sec).Here,we review the recent progressof hematite photoanodes for PEC water oxidation,focused on enhancing surface water oxidation reaction,accelerating charge separation and transport in bulk,improving light absorption.Finally,perspectives on the key challenges and future development of hematite photoelectrodes for PEC water splitting are given.