High-speed Charge Transfer Research Articles

Electrochemical behavior and reaction mechanism of nano-BiOBr/rGO composite micro flower with strong interface coupling as potassium-ion battery anodes

To explore the potential of bismuth oxybromide (BiOBr) as anodes for high-performance potassium (K)-ion batteries and understand its potassium storage mechanism, a novel nano-BiOBr/reduced graphene oxide (rGO) composite micro flower (labelled as SI-coupled nano-BiOBr/rGO micro flower), where nano-BiOBr slices are firmly anchored on rGO by strong interface coupling, is constructed. Unique microstructure accompanied by C-Bi bonds at the interface between BiOBr and rGO endows it with abundant high-speed charge transfer channels and excellent structural stability. As a result, it exhibits an excellent rate performance (a high reversible capacity of 278 mAh/g at 5 A/g) and a remarkable long-term cycling stability maintaining 95.4 % after 1000 cycles at 2.5 A/g. Furthermore, it is also found that SI-coupled nano-BiOBr/rGO micro flower anode undergoes intercalation, conversion, and alloying (BiOBr → KzBiOBr → Bi → KBi2 → K3Bi2 → K3Bi) at the initial discharge process, and the subsequent charge process is only reversible dealloying and conversion reaction (K3Bi → K3Bi2 → KBi2 → Bi → BiOxBry). This work not only demonstrates the large potential of BiOBr as high-performance K-ion battery anodes, but also elucidates for the first time its K storage mechanism.

Insight into the unique role of silver single-atom in atomic-thickness ZnIn2S4/g-C3N4 Van der Waals heterojunction for photocatalytic hydrogen evolution

The construction of ultra-close 2D atomic-thickness Van der Waals heterojunctions with high-speed charge transfer still faces challenges. Here, we synthesized single-layer ZnIn2S4 and g-C3N4, and introduced silver single atoms to regulate Van der Waals heterojunctions at the atomic level to optimize charge transfer and catalytic activity. At the atomic scale, the impact of detailed structural differences between the two characteristic surfaces of ZnIn2S4 ([Zn-S4] and [In-S4]) on catalytic performance has been first proposed. Experiments combined with the DFT study demonstrate that single atom Ag not only acts as a charge transfer bridge but also regulates the energy band and intrinsic catalytic activity. Benefiting from the enhanced electron delocalization, the synthesized catalyst ZIS/Ag@CN exhibits excellent photocatalytic performance, with a hydrogen production rate of 5.50 mmol·g−1·h−1, which is much higher than the reported Ag-based single-atom catalysts so far. This work provides a new understanding of atomic-level heterojunction interface regulation and modification.

Constructing Dual-Phase Co9S8-CoMo2S4 Heterostructure as an Efficient Trifunctional Electrocatalyst for Oxygen Reduction, Oxygen Evolution and Hydrogen Evolution Reactions.

Designing robust, efficient and inexpensive trifunctional electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is significant for rechargeable zinc-air batteries and water-splitting devices. To this end, constructing heterogenous structures based on transition metals stands out as an effective strategy. Herein, a dual-phase Co9S8-CoMo2S4 heterostructure grown on porous N, S-codoped carbon substrate (Co9S8-CoMo2S4/NSC) via a one-pot synthesis is investigated as the trifunctional ORR/OER/HER electrocatalyst. The optimized Co9S8-CoMo2S4/NSC2 exhibits that ORR has a half-wave potential of 0.86 V (vs. RHE) and the overpotentials at 10 mA cm-2 for OER and HER are 280 and 89 mV, respectively, superior to most transition-metal based trifunctional electrocatalysts reported to date. The Co9S8-CoMo2S4/NSC2-based zinc-air battery (ZAB) has a high open-circuit voltage (1.41 V), large capacity (804 mA h g-1) and highly stable cyclability (97 h at 10 mA cm-2). In addition, the prepared Co9S8-CoMo2S4/NSC2-based ZAB in series can self-drive the corresponding water electrolyzer. The dual-phase Co9S8-CoMo2S4 heterostructure provides not only multi-type active sites to drive the ORR, OER and HER, but also high-speed charge transfer channels between two phases to improve the synergistic effect and reaction kinetics.

Defect-induced atomic-level intimate interface of a hollow Ov-CeO2/CdS photocatalyst with a Z-scheme to boost hydrogen evolution

Construction of Z-scheme heterojunction catalysts with high-speed charge transfer channels for efficient photocatalytic hydrogen production from water splitting is still a challenge. In this work, a lattice-defect-induced atom migration strategy is proposed to construct an intimate interface. The oxygen vacancies of cubic CeO2 obtained from a Cu2O template are used to induce lattice oxygen migration and form SO bonds with CdS to form a close contact heterojunction with a hollow cube. The hydrogen production efficiency reaches ∼12.6 mmol·g−1·h−1 and maintains a high value over 25 h. A series of photocatalytic tests combined with density functional theory (DFT) calculations show that the close contact heterostructure not only promotes the separation/transfer of photogenerated electron-hole pairs but also regulates the intrinsic catalytic activity of the surface. A large number of oxygen vacancies and SO bonds at the interface participate in charge transfer, which accelerates the migration of photogenerated carriers. The hollow structure improves the ability to capture visible light. Therefore, the synthesis strategy proposed in this work, as well as the in-depth discussion of the interface chemical structure and charge transfer mechanism, provides new theoretical support for the further development of photolytic hydrogen evolution catalysts.

Fe-Decorated Nitrogen-Doped Carbon Nanospheres as an Electrochemical Sensing Platform for the Detection of Acetaminophen.

In this work, Fe-decorated nitrogen-doped carbon nanospheres are prepared for electrochemical monitoring of acetaminophen. Via a direct pyrolysis of the melamine-formaldehyde resin spheres, the well-distributed Fe-NC spheres were obtained. The as-prepared Fe-NC possesses enhanced catalysis towards the redox of acetaminophen for abundant active sites and high-speed charge transfer. The effect of loading Fe species on the electrochemical sensing of acetaminophen is investigated in detail. The synergistic effect of nitrogen doping along with the above-mentioned properties is taken advantage of in the fabrication of electrochemical sensors for the acetaminophen determination. Based on the calibration plot, the limits of detection (LOD) were calculated to be 0.026 μM with a linear range from 0-100 μM. Additionally satisfactory repeatability, stability, and selectivity are obtained.

A CMOS Lock-In Pixel Image Sensor With Multisimultaneous Gate for Time-Resolved Near-Infrared Spectroscopy

This article proposes a CMOS lock-in pixel image sensor aiming for time-resolved near-infrared spectroscopy (TR-NIRS). The pixel employs lateral electric field charge modulation (LEFM) with an eight-tap multisimultaneous gate structure and negative substrate bias. The optimization of pixel structure creates a high potential slope with no barrier to facilitate the high-speed photo-generated charge transfer required in the time-resolved application. The sensor employs a two-stage charge transfer architecture with pinned storage diodes (SDs). The effectiveness of the sensor is demonstrated through simulations and experimental measurements. A prototype sensor with 70 (V) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times110$ </tex-math></inline-formula> (H) effective pixels to characterize the multisimultaneous gate lock-in pixel is implemented in a 0.11- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> 1-poly-4-metal CMOS image sensor (CIS) technology. A fast intrinsic response of 240 ps is achieved using an 80-ps pulsewidth 780-nm laser diode by the characterization using two simultaneous gates and a single time window of the lock-in pixel. Performance evaluation using silicon phantoms and further measurement with a rat demonstrates the feasibility of the proposed sensor and setup for TR-NIRS applications.

Fe doped g-C3N4 composited ZnIn2S4 promoting Cr(VI) photoreduction

30% FeCN/ZIS (30% Fe doped g-C3N4 composited ZnIn2S4) was synthesized by a simple water bath method, via in-situ growth of abundant well-dispersed ZnIn2S4 nanosheets on the Fe doped g-C3N4 surface. Experimental results showed the optimized 30% FeCN/ZIS achieved the best photoreduction of Cr(VI) performance within a wide pH range, which was 9.5 times and 700 times higher than that of pure ZnIn2S4 and 30% FeCN (Fe doped g-C3N4). This is due to the intense synergy between the Fe-Nx bond and close interface contact produces a high-speed charge transfer channel, thus significantly improving the efficiency of optical carrier separation and migration. Meanwhile, UV-vis diffuse reflection spectra and photoluminescence spectroscopy showed that iron doping significantly narrowed the bandgap of g-C3N4, preventing electron-hole pair recombination. Further, the microstructures and charge separation properties were analyzed by scanning electron microscope, Photoluminescence Spectroscopy and time-resolved photoluminescence, which revealed the structure-activity relationship of composite structure and the synergistic mechanism of each functional component. This research should provide a viable technique for creating composites with high photocatalytic activity for the treatment of chromium-containing wastewater.

In situ self-assembly of mesoporous Zn-Cd-Mo-S quaternary metal sulfides with double heterojunction synergistic charge transfer for boosting photocatalytic hydrogen production

The construction of semiconductor heterojunctions is regarded as an efficient strategy for promoting photogenerated carrier transfer and enhancing photocatalytic performance. [1] Moreover, the in-situ self-assembly method of the main catalyst and the cocatalyst is believed to overcome the shortcomings of the traditional surface loading method and provide a more efficient hydrogen evolution reaction capability. In this work, Zn-Cd-Mo-S quaternary metal sulfide mesoporous nanospheres were generated by in-situ self-assembly via a one-step mild hydrothermal method. A photocatalyst with a double-heterojunction synergistic structure and a large specific surface area was constructed to form a high-speed charge transfer channel as a mechanism to promote photocatalytic hydrogen production. The best quaternary catalyst ZCM5S has a hydrogen evolution yield of 23.32 mmol h−1 g−1, which is 53 times and 11 times that of the corresponding binary (CdS) and ternary (ZnCdS) metal sulfides, respectively, and still has high stability within 20 h. Furthermore, the ZCM5S gets an apparent quantum efficiency (AQE) of 6.9 % at 420 nm. Through further analysis, such as photoluminescence (PL) and photoelectrochemical, etc., the enhanced photocatalytic performance of ZCM5S can be attributed to the synergistic effect of the heterojunction between ZnS and CdS and the heterojunction between ZnCdS and MoS2. In addition, the Pt-like structure of molybdenum sulfide cocatalyst can lead to efficient photoinduced charge separation and transfer. Meanwhile, the mesoporous structure endows the material with abundant reactive sites and increases the catalytic reaction efficiency. The unique in situ construction method of this work also provides a reference for the design and synthesis of heterojunction quaternary catalysts for green energy conversion.

Fabrication of a ternary NiS/ZnIn2S4/g-C3N4 photocatalyst with dual charge transfer channels towards efficient H2 evolution

As a renewable green energy, hydrogen has received widespread attention due to its huge potential in solving energy shortages and environment pollution. In this paper, a one-step solvothermal method was applied to grow ultra-thin g-C3N4 (UCN) nanosheets and NiS nanoparticles on the surface of ZnIn2S4 (ZIS). A ternary NiS/ZnIn2S4/ultra-thin-g-C3N4 composite material with dual high-speed charge transfer channels was constructed for the advancement of the photocatalytic H2 generation. The optimal ternary catalyst 1.5wt.%NiS/ZnIn2S4/ultra-thin-g-C3N4 (NiS/ZIS/UCN) achieved a H2 evolution yield reached to 5.02 mmolg−1h−1, which was 5.23 times superior than that of pristine ZnIn2S4 (0.96 mmolg−1h−1) and even outperform than that of the best precious metal modified 3.0 wt%Pt/ZnIn2S4 (4.08 mmolg−1h−1). The AQY at 420 nm could be achieved as high as 30.5%. The increased photocatalytic performance of NiS/ZIS/UCN could be ascribed to the type-I heterojunctions between intimated ZIS and UCN. In addition, NiS co-catalyst with large quantity of H2 evolution sites, could result in efficient photo-induced charges separation and migration. Furthermore, the NiS/ZIS/UCN composite exhibited excellent H2 evolution stability and recyclability. This work would also offer a reference for the design and synthesis of ternary co-catalyst with heterojunction composite for green energy conversion.

Well-designed efficient charge separation in 2D/2D N doped La2Ti2O7/ZnIn2S4 heterojunction through band structure/morphology regulation synergistic effect

La2Ti2O7, a layered perovskite material, has attracted much attention in photocatalytic hydrogen production due to its high stability and non-toxic. Combing La2Ti2O7 with narrow band gap semiconductors to construct 2D/2D heterojunction is a facile strategy to improve photocatalytic activity. In this work, we first report a novel 2D/2D N–La2Ti2O7/ZnIn2S4 heterojunction via in-situ growth of abundant well-dispersed ZnIn2S4 nanosheets on the N–La2Ti2O7 nanosheets surface. Experimental results show the optimized 2D/2D N–La2Ti2O7/ZnIn2S4 sample exhibits the best light-driven H2 evolution activity, which is nearly 5.2 and 1.7 times higher than that of pristine ZnIn2S4 and 2D/2D La2Ti2O7/ZnIn2S4 samples, respectively. This is due to the unique 2D/2D heterojunction produces high-speed charge transfer channels, thus significantly enhancing photo-carriers separation and migration efficiency. Meanwhile, DFT calculations confirm nitrogen doping forms impurity energy states at the top of valence band, thus narrowing the band gap of La2Ti2O7, considerably inhibiting electron-hole pair recombination. Further the microstructures and charge separation properties are analyzed by SEM, PL, and DFT calculations to reveal the structure-activity relationship of hetero-structure and the synergistic mechanism of each functional component. This report will hopefully provide a practical strategy for designing heterojunction composite for high light-driven hydrogen evolution rate.

Enhanced defect oxygen of LaFeO3/GO hybrids in promoting persulfate activation for selective and efficient elimination of bisphenol A in food wastewater

The unintended leakage of BPA into food waste has posed a new challenge to ecological and human health, but regrettably, the public has not paid much attention to the BPA elimination in food wastewater. Herein, we explored a facile chemical/thermal strategy for synthesizing perovskite LaFeO3/graphene oxide (LaFeO3/GO) hybrids, selectively capturing and efficiently removing BPA in food wastewater. Strikingly, LaFeO3/GO activating persulfate system exhibited complete BPA degradation efficiency with a higher rate constant of 0.1074 min−1, approximately 18.2 times than that of pristine LaFeO3. The surprisingly high stability at pH value up to 9.0 expanded the use of catalysts in alkaline conditions. Compared to LaFeO3, LaFeO3/GO can selectively enrich the hydrophobic BPA molecules thanks to the hydrophobicity of benzene rings in GO, which was not disturbed by other hydrophilic substances in the complex food wastewater. Furthermore, high-speed charge transfer, more defect oxygen species and synergistic effects between La and Fe in LaFeO3/GO boosted the generation of radical (OH, SO4·-, O2·-) and nonradical (1O2), efficiently removing 97% BPA and 51% total organic carbon (TOC) in food wastewater. The biological acute toxicity decreased significantly during the oxidation reaction, consistent with the BPA transformation pathway analyzed by HPLC-MS. This system possessed a remarkable performance in extremely intricate food wastewater, so it might be also available for other various organic contaminants in waters and wastewaters.

Construction of ultrathin 2D/2D g-C3N4/In2Se3 heterojunctions with high-speed charge transfer nanochannels for promoting photocatalytic hydrogen production

Reinforcing the photo-induced carrier separation and interfacial charge transfer are the pressing issue to elevate the photocatalyic hydrogen evolution efficiency of g-C3N4-based catalysts. To this end, a binary nanohybrid heterojunction of two-dimensional (2D) g-C3N4 and In2Se3 (g-C3N4/In2Se3-X) was designed and used as the visible light photocatalyst. Benefited from the intimate 2D/2D heterojunction interface and the spontaneous polarization characteristic of ultrathin In2Se3 nanosheet, the g-C3N4/In2Se3 heterojunction could generate numerous high-speed charge transfer channels, and the vertical intrinsic electric field of In2Se3 would considerably inhibit the recombination of photogenerated charge. By taking advantage of these features, the 2D/2D g-C3N4/In2Se3 heterojunction nanosheets exhibited remarkably intensified visible-light-driven photocatalytic activity, the optimal g-C3N4/In2Se3 heterojunction nanosheets exhibit a hydrogen evolution rate of 4.8 mmol·g−1·h−1 that greatly higher than pure g-C3N4 (0.94 mmol·g−1·h−1) and In2Se3. The photocatalytic mechanism and high-speed channels of interface charge transfer were investigated and discussed. This work can provide a possibility for design and construction of photocatalysts with high efficient separation of photoinduced carriers.

Fabrication of porous Na3V2(PO4)3/reduced graphene oxide hollow spheres with enhanced sodium storage performance

Sodium-ion batteries (SIBs) have long been recognized as a potential substitute for lithium-ion batteries, while their practical application is greatly hindered owing to the absence of suitable cathode materials with improved rate capability and prolonged cycling life. Na3V2(PO4)3 (NVP) has drawn extensive attention among the cathode materials for SIBs because of its fast Na+-transportable framework which enables high-speed charge transfer, but the poor electric conductivity of NVP significantly restricts the Na+ diffusion. To tackle this issue, in this work, porous NVP/reduced graphene oxide hollow spheres (NVP/rGO HSs) are constructed via a spray drying strategy. Due to the unique porous hollow architecture, the synthesized compound manifests a high reversible capacity of 116 mAh g−1 at 1 C (1 C = 118 mA g−1), an outstanding high-rate capability of 107.5 mAh g−1 at 10 C and 98.5 mAh g−1 at 20 C, as well as a stable cycling performance of 109 mAh g−1 after 400 cycles at 1 C and 73.1 mAh g−1 after 1000 cycles at 10 C. Moreover, galvanostatic intermittent titration technique demonstrates that the Na+ diffusion coefficient of NVP/rGO HSs is an order of magnitude larger than the pristine NVP. The remarkable electrochemical properties of NVP/rGO HSs in full cells further enable it a potential cathode for SIBs.

Ag as Cocatalyst and Electron-Hole Medium in CeO2 QDs/Ag/Ag2Se Z-scheme Heterojunction Enhanced the Photo-Electrocatalytic Properties of the Photoelectrode.

A recyclable photoelectrode with high degradation capability for organic pollutants is crucial for environmental protection and, in this work, a novel CeO2 quantum dot (QDs)/Ag2Se Z-scheme photoelectrode boasting increased visible light absorption and fast separation and transfer of photo-induced carriers is prepared and demonstrated. A higher voltage increases the photocurrent and 95.8% of tetracycline (TC) is degraded by 10% CeO2 QDs/Ag2Se in 75 minutes. The degradation rate is superior to that achieved by photocatalysis (92.3% of TC in 90 min) or electrocatalysis (27.7% of TC in 90 min). Oxygen vacancies on the CeO2 QDs advance the separation and transfer of photogenerated carriers at the interfacial region. Free radical capture tests demonstrate that •O2−, •OH, and h+ are the principal active substances and, by also considering the bandgaps of CeO2 QDs and Ag2Se, the photocatalytic mechanism of CeO2 QDs/Ag2Se abides by the Z-scheme rather than the traditional heterojunction scheme. A small amount of metallic Ag formed in the photocatalysis process can form a high-speed charge transfer nano channel, which can greatly inhibit the photogenerated carrier recombination, improve the photocatalytic performance, and help form a steady Z-scheme photocatalysis system. This study would lay a foundation for the design of a Z-scheme solar photocatalytic system.

Anchoring single-unit-cell defect-rich bismuth molybdate layers on ultrathin carbon nitride nanosheet with boosted charge transfer for efficient photocatalytic ciprofloxacin degradation

Photocatalysis technology is regarded as a promising way for environmental remediation, but rationally designing photocatalysis system with high-speed interfacial charge transfer, sufficient photoabsorption and surface reactive sites is still a challenge. In this study, anchoring single-unit-cell defective Bi2MoO6 on ultrathin g-C3N4 to form 2D/2D heterostructure system is a triple-purpose strategy for high-performance photocatalysis. The defect structure broadens photo-responsive range. The large intimate contact interface area between two monomers promotes charges carrier transfer. The enhanced specific surface area exposes more reactive sites for mass transfer and catalytic reaction. As a result, the obtained heterostructure displays excellent photocatalytic performance for ciprofloxacin (CIP) (0.0126 min−1), which is 3.32 and 2.93 folds higher than Bi2MoO6 and g-C3N4. In addition, this heterostructure retains high-performance for actual wastewaters treatment, and it displays strong mineralization ability. And this heterojunction also exhibits excellent photostability based on cyclic experiment. Mechanism exploration reveals that hole, superoxide radical, and hydroxyl radical are chief reactive species toward CIP degradation, thereby a Z-scheme charge carrier transfer channel is proposed. In addition, the intermediates and degradation pathways of CIP are tracked by liquid chromatography-triple quadrupole tandem mass spectrometry (LCMS/MS) and three-dimensional excitation-emission matrix fluorescence spectroscopy (3D EEMs). This study paves new way to design and construct atomic level 2D/2D heterojunction system for environment remediation.

Heterostructured WO3/RGO/protonated g-C3N4 three-layer nanosheets for enhanced visible-light photocatalytic activity

The novel WO3/RGO/protonated g-C3N4 (PCN) composites with a 2D/2D/2D architecture were successfully prepared through a microwave-assisted hydrothermal method. The 2D/2D/2D heterojunction exhibited a short charge migration path and a wide interface contact area, which could produce a large number of intimate high-speed charge transfer channels and enhance bulk-to-surface and interfacial charge transfer abilities. The WO3/RGO/PCN composites displayed dramatically improved photodegradation performance for tetracycline hydrochloride (TC-HCL) under illuminating of visible light as compared to PCN, WO3, as well as binary RGO/PCN and WO3/PCN heterojunctions. The photocatalytic mechanism was confirmed by photoluminescence spectra (PL), photocurrent response, electron spin resonance spectra (ESR) and electrochemical impedance spectroscopy (EIS). The synergistic effect of 2D/2D/2D architecture and Z-Scheme electron migration mechanism greatly boosts the migration and separation of photoexcited charge carriers that leads to the enhanced photodegradation activity.

Computationally guided synthesis of (2D/3D/2D) rGO/Fe2O3/g-C3N4 nanostructure with improved charge separation and transportation efficiency for degradation of pharmaceutical molecules

In this study, we designed and successfully prepared all solid state 2D/3D/2D rGO/Fe2O3/g-C3N4 nanocomposite by embedding 3D Fe2O3 nanoparticles on 2D g-C3N4 nanosheets to for 3D/2D Fe2O3/g-C3N4 followed by the addition of 2D rGO nanosheets via a simple hydrothermal technique with the support of response surface methodology for the first time. The formation of this unique 2D/3D/2D heterojunction leads to generate several nanochannels in their interfacial contact for high-speed photoinduced charge transfer. The considerable enhancement in photoinduced charge transportation and migration efficiency resulted in significant visible-light-driven degradation of emerging pharmaceutical condemnations. The 3D/2D Fe2O3/g-C3N4 nanocomposite was optimized by various concentrations of Fe2O3 in g-C3N4, followed by the optimization of rGO concentration in 2D/3D/2D rGO/Fe2O3/g-C3N4 nanocomposite to obtain maximum degradation efficiency. We observed that the 3% of rGO in 4% Fe2O3/g-C3N4 nanocomposite exhibited superior photocatalytic ability, nearly 22 times and 16 times higher than pristine g-C3N4 nanosheets towards tetracycline and ciprofloxacin degradation, respectively. The synergistic effect between 2D/3D/2D g- rGO/Fe2O3/g-C3N4 nanocomposites and the photocatalytic mechanism was well studied through various characterization techniques like XRD, FTIR, SEM-EDX-mapping, HR-TEM, UV–vis DRS, PL, XPS and EPR. In addition, the 2D/3D/2D rGO/Fe2O3/g-C3N4 nanocomposite exhibits excellent recyclability and stability, establishing a promising application in environmental remediation. This research would provide a noteworthy platform for the extensive photocatalytic properties of 2D/3D/2D heterojunction nanocomposite system with enhanced charge migration and separation.

Hierarchical heterojunction structures based-on layered Sb2Te3 nanoplate@rGO for extended long-term life and high-rate capability of sodium batteries

Three dimensional (3D) hierarchical heterojunction structures were successfully constructed for sodium batteries (SIBs) based on reduced oxidized graphene (rGO) and layered Sb2Te3 nanoplate grown on high electric and flexible copper substrate (Cu@Sb2Te3@rGO). The specific structure can endow electrode material with attractive properties in high-speed charge transfer, fast electronic transport and good stability due to the high conductivity of copper substrate, built-in electric field providing a driving force for charge transfer and the restriction of volume expansion by a 3D hierarchical structure. The binderless and flexible Cu@Sb2Te3@rGO electrode can deliver a superior reversible capacity of 425mAhg−1 after 200 cycles at a current density of 200mAg−1, an excellent rate capability of 220mAhg−1 at 15Ag−1, even a fascinating capacity of 410mAhg−1 at 2Ag−1 after 1000 cycles. This 3D hierarchical heterojunction structure electrode of Cu@Sb2Te3@rGO can hold great promise for high cycling and rate capacity performance of SIBs.

Construction of 2D heterojunction system with enhanced photocatalytic performance: Plasmonic Bi and reduced graphene oxide co-modified Bi5O7I with high-speed charge transfer channels.

The efficient electron-hole charge pair separation, ultra-fast electron migration and excellent light harvest capacity are essential for semiconductor photocatalyst with superior photocatalytic performance. In this study, we constructed layered 2D/2D heterojunction composite of Bi@Bi5O7I/rGO (BiBGOI) through a facile surface charge mediated self-assembly strategy. The unique 2D/2D heterostructure with face to face contact can increase the contact area and generate a large amount of charge transfer nanochannels in the interfacial heterojunction, resulting in the enhancement of photocatalytic activity. Addition of semimetal Bi can enhance light absorption, and the local electromagnetic field dominated by SPR effect is favorable for photoinduced charge pair separation. The novel composite showed superior photocatalytic performance for decomposing levofloxacin (LVFX), which was attributed to the unique 2D/2D structure and SPR effect. The enhanced mineralization ability of the novel composite was ascribed to the strong oxidization ability of photoinduced holes, further evaluating high charge pair separation efficiency. In addition, the strong adsorption capacity of rGO for LVFX molecules can enable active radicals transfer into the surface to decompose it. This work will shed light on constructing 2D/2D heterojunction system assisted with SPR effect for the practical application in removal of organic pollutants.

New Magnetically Recyclable Reduced Graphene Oxide rGO/MFe2 O4 (M= Ca, Mg)/Ag3 PO4 Nanocomposites With Remarkably Enhanced Visible-light Photocatalytic Activity and Stability.

New magnetically separable CaFe2 O4 /Ag3 PO4 , MgFe2 O4 /Ag3 PO4 , rGO/CaFe2 O4 /Ag3 PO4 and rGO/MgFe2 O4 /Ag3 PO4 photocatalysts were synthesized by the hydrothermal and ion-exchange deposition method. These four types of photocatalyst were used for degradation of Methylene blue (MB), Methyl orange (MO) and 4-chlorophenol (4-CP) in aqueous solution under visible-light illumination. The optimized photocatalyst, i.e. rGO/CaFe2 O4 /Ag3 PO4 with a mass ratio of (1:3:9) composite not only shows the highest photocatalytic performance for the degradation of MB, MO and 4-CP under visible light irradiation among the other synthesized photocatalysts but also exhibits high reusability and stability for at least five cycles. It was found that the impressive separation of electron-hole pairs as well as presence of rGO sheets which act as a high speed charge transfer were responsible for increasing photocatalytic activity over the optimized photocatalyst under visible-light irradiation. A possible mechanism for the increased photocatalytic activity of the rGO/CaFe2 O4 /Ag3 PO4 with a mass ratio of (1:3:9) composite was discussed in detail.