Fast Charge Transfer Research Articles

Multiple Bubble Removal Strategies to Promote Oxygen Evolution Reaction: Mechanistic Understandings from Orientation, Rotation, and Sonication Perspectives.

Bubble coverage of catalytically active sites is one of the well-known bottlenecks to the kinetics of the oxygen evolution reaction (OER). Herein, various bubble removal approaches (electrode orientation, rotating, and sonication) were considered for the OER performance evaluation of a state-of-the-art Ir-based electrocatalyst. Key parameters, such as catalyst mass loss, activity, overpotential, and charge- and mass-transfer mechanisms, were analyzed. First, it was suggested that a suitable orientation of the working electrode facilitates coalescence and sliding bubble effects on the catalyst surface, leading to better electrochemical performance than those of the traditional rotating disk electrode (RDE) configuration. Then, the convection and secondary Bjerknes force were explained as the responsible phenomena in improving the OER activity in the RDE and sonication methods. Finally, simultaneous implementation of the methods enhanced the catalyst mass activity up to 164% and provided fast charge-transfer kinetics and low double-layer capacitance, which eventually led to a 22% reduction in overpotential, while the catalyst loss slightly increased from 1.93 to 3.88%.

Boosting the electrochemical CO2 reduction performance by Cu2O/β-Bi2O3 bimetallic heterojunction with the assistance of light

CO2, as one of the greenhouse gases, actually represents a cheap and abundant C1 fuel to produce fuels and chemical stocks. Herein, inspired by photocatalysis and electrocatalysis, we have successfully synthesized a series of copper and bismuth oxides with heterostructure by a first co-electrodeposition method and then by thermal treatment at different temperatures. The bimetallic oxide (Cu2O/β-Bi2O3) at 300 °C with the main exposure of β-Bi2O3 (201) planes shows the beautiful micro-flower morphology with numerous petals in thickness around 20 ∼ 40 nm. Therefore, the Cu2O/β-Bi2O3 heterostructure with active edge sites can electrochemically convert CO2 into formate with a promising Faradaic efficiency (96.3 %) and current density (40.4 mA cm−2) at − 0.97 V vs. RHE. Specifically, the current density of Cu2O/β-Bi2O3 bimetallic catalyst can be largely enhanced to 48.5 mA cm−2 at − 0.92 V vs. RHE with the assistance of light compared to the 30.1 mA cm−2 without light. The production rate of formate with the assistance of light can also be increased to 705.1 μmol h−1 cm−2, superior to that of 536.4 μmol h−1 cm−2 without light. Such an excellent photo-assisted electrochemical CO2 reduction performance is due to the fast charge-transfer process between Cu2O and β-Bi2O3. This study may provide a new route to directly synthesize the photoactive electrocatalysts with more edge sites and heterojunction for promoting electrochemical CO2 reduction performance with the assistance of light field.

Modulated Connection Modes of Redox Units in Molecular Junction Covalent Organic Frameworks for Artificial Photosynthetic Overall Reaction.

The precise tuning of components, spatial orientations, or connection modes for redox units is vital for gaining deep insight into efficient artificial photosynthetic overall reaction, yet it is still hard achieve for heterojunction photocatalysts. Here, we have developed a series of redox molecular junction covalent organic frameworks (COFs) (M-TTCOF-Zn, M = Bi, Tri, and Tetra) for artificial photosynthetic overall reaction. The covalent connection between TAPP-Zn and multidentate TTF endows various connection modes between water photo-oxidation (multidentate TTF) and CO2 photoreduction (TAPP-Zn) centers that can serve as desired platforms to study the possible interactions between redox centers. Notably, Bi-TTCOF-Zn exhibits a high CO production rate of 11.56 μmol g-1 h-1 (selectivity, ∼100%), which is more than 2 and 6 times higher than those of Tri-TTCOF-Zn and Tetra-TTCOF-Zn, respectively. As revealed by theoretical calculations, Bi-TTCOF-Zn facilitates a more uniform distribution of energy-level orbitals, faster charge transfer, and stronger *OH adsorption/stabilization ability than those of Tri-TTCOF-Zn and Tetra-TTCOF-Zn.

A Plant Dye for Photocatalytic Methane Conversion.

A metal-free natural dye has been developed to selectively convert methane to methyl trifluoroacetate (CH3 TFA) using visible light, probably due to the formation of a chloride-bridged dimer undergoing fast intra-complex charge transfer.

Boosting adsorption and dissociation kinetics of magnesium-chloride ion pair via bismuth/indium-based artificial interface

The formation of passivating interphases on Mg-metal anode is impeding the wide employment of rechargeable Mg-metal batteries with less safety and cost concerns. Despite engineering artificial interlayers offers an efficient solution, it still falls short of expectation because of the compromised Mg plating/stripping performances in conventional electrolyte systems. In this work, a unique bismuth/indium-based artificial interface is introduced, which enables an exceptional reversibility (lowest nucleation overpotential of 189 mV than that (583 mV) of pristine Mg anode), high rate capability (a stable charge and discharge operation at 5.0 mA cm−2 without short circuit) and good temperaturetolerance (being cyclable over 10 °C and 50 °C) for the first time. This bismuth/indium-based artificial interface is constructed by facile displacement reactions between Bi(CF3SO3)3/In(CF3SO3)3 and Mg. The dominant interphases, including Bi, In and BiOx species, can be controllably tailored via adjusting the relative ratio and concentration of Bi(CF3SO3)3/In(CF3SO3)3. Theoretical calculation results accompanied by electrochemical experiments indicate that kinetically favorable adsorption and dissociation processes of Mg-Cl ion pair on this interface, affording good magnesiophilic property and fast charge transfer kinetics, are responsible for the improved Mg-metal anode properties.

Application of superhydrophobic Ti3C2 Mxene-based screen-printed ion-selective electrode for determination of Ca2+ concentration

Ti3C2 Mxene is a remarkable electrochemical material owing to its high conductivity, large specific surface area, and high electrical capacity. It can be applied in all-solid-state ion-selective electrodes to improve the ion-electron conversion efficiency and reduce the resistance. However, Ti3C2 Mxene is hydrophilic, which will form a water layer between the ion-selective membrane and the substrate, resulting in response potential drift. In this study, Ti3C2 Mxene functionalized with octadecyltrichlorosilane was developed as the ion-electron conversion layer (solid contact layer), and a polymer membrane containing N, N, N', N' -Tetracyclohexyl-3-oxapentanediamide was used as the Ca2+ selective membrane on a screen-printed electrode substrate. An all-solid Ca2+-selective electrode (SPE/SH-Ti3C2/Ca-ISM) was prepared. The results from cyclic voltammetry and electrochemical impedance spectroscopy proved the high capacitance and fast charge transfer ability of the Ti3C2 Mxene modified electrode. In addition, it shows good performance in the water layer test and anti-interference test and improves the response speed and stability of potential. The linear response range of this disposable screen-printed electrode to Ca2+ is 10−6∼10−1 M, the detection limit is 10−6.2 M, and the response time is about 15 s. The electrode can accurately and quickly determine the level of Ca2+ in serum samples of dairy cows.

High-Density CuInS2 Quantum Dots for Efficient and Stable CO2 Electroreduction.

Electrochemically converting CO2 back into fuels and chemicals is promising in alleviating the greenhouse effect worldwide. Various high-efficiency catalysts have been achieved, yet the unsatisfied structural stability under CO2 electrolysis conditions restricts their practical application. Herein, a sub-5nm sized CuInS2 quantum dots (CIS-QDs) based electrocatalyst for converting CO2 into CO are developed. Taking advantage of the stable M─Ch (metal-chalcogenide) covalent bonds, and unique p-block metal properties, the as-prepared catalyst exhibits excellent structural stability under large overpotentials and can achieve a high CO Faradaic efficiency (FE) of 86% (total CO2 reduction FE of 89%) at -0.65V versus reversible hydrogen electrode with long-term durability of 40h and outstanding current densities of 10.6mAcm-2 simultaneously. Furthermore, detailed electrochemical analyses revealed that the excellent performance of the as-prepared catalysts shall be attributed to the high-density active sites and fast charge transfer brought by the ultrasmall size of CIS-QDs. This work provides insights into the design of high-density and stablecatalytic sites for developing high-performance electrocatalysts.

Excellent ion storage properties of copper-cobalt composite selenide heterostructure in magnesium/lithium hybrid battery

Rechargeable magnesium batteries (RMBs) have emerged as a promising alternative to lithium-ion batteries (LIBs), given their high abundance and desirable safety characteristics. However, the strong polarization of divalent ions has hindered the satisfactory insertion and dissolution of Mg2+ ions in the cathode, thereby limiting the electrochemical performance of the system. To address this issue, magnesium/lithium hybrid batteries (MLHB) have been developed, using both Mg2+ and Li+ ions as carriers to enhance the electrochemical kinetic performance and maintain safety. In this study, a Cu2Se/CoSe heterostructured cathode is designed to extremely promote the electrochemical performance of MLHB. When it is applied to MLHB, the battery exhibites extremely high initial discharge capacity, reversible capacity and cycling stability. The initial discharge capacity obtains 385 mAh g−1 at 100 mA g−1, and a reversible capacity of 140 mAh g−1 is maintained after 200 cycles. The role of the special heterostructures and the effect of pre-lithiation on cathode materials are discussed in detail, on the basis of which a two-step storage mechanism of hybrid ions in Cu2Se/CoSe is proposed. This work lays the foundation for designing and constructing high-capacity, excellent cycle stability cathodes with fast charge-transfer kinetics.

Ru-Cu Nanoheterostructures for Efficient Hydrogen Evolution Reaction in Alkaline Water Electrolyzers.

Combining multiple species working in tandem for different hydrogen evolution reaction (HER) steps is an effective strategy to design HER electrocatalysts. Here, we engineered a hierarchical electrode for the HER composed of amorphous-TiO2/Cu nanorods (NRs) decorated with cost-effective Ru-Cu nanoheterostructures (Ru mass loading = 52 μg/cm2). Such an electrode exhibits a stable, over 250 h, low overpotential of 74 mV at -200 mA/cm2 for the HER in 1 M NaOH. The high activity of the electrode is attributed, by structural analysis, operando X-ray absorption spectroscopy, and first-principles simulations, to synergistic functionalities: (1) mechanically robust, vertically aligned Cu NRs with high electrical conductivity and porosity provide fast charge and gas transfer channels; (2) the Ru electronic structure, regulated by the size of Cu clusters at the surface, facilitates the water dissociation (Volmer step); (3) the Cu clusters grown atop Ru exhibit a close-to-zero Gibbs free energy of the hydrogen adsorption, promoting fast Heyrovsky/Tafel steps. An alkaline electrolyzer (AEL) coupling the proposed cathode and a stainless-steel anode can stably operate in both continuous (1 A/cm2 for over 200 h) and intermittent modes (accelerated stress tests). A techno-economic analysis predicts the minimal overall hydrogen production cost of US$2.12/kg in a 1 MW AEL plant of 30 year lifetime based on our AEL single cell, hitting the worldwide targets (US$2-2.5/kgH2).

Electrocatalytic and photocatalytic activities of hierarchically structured zinc oxide nanoparticles derived from cellulose paper-precipitated hydrozincite

This study presents a novel method for synthesizing hierarchical porous zinc oxide (ZnO) nanostructures by thermally decomposing green-synthesized hydrozincite. The hydrozincite was prepared at room temperature using zinc acetate dihydrate and calcium carbonate (CaCO3) in cellulose printing papers as the precipitating agent. The resulting ZnO particles exhibit a distinctive flower-like morphology, consisting of porous nanosheets composed of interconnected nanoparticles. The average crystallite size of the hierarchically structured zinc oxide nanoparticles, as determined via X-ray diffraction Rietveld refinement method, was found to be 18.8 nm when calcined at 500 °C. However, with increasing calcination temperature to 600, 700, and 800 °C, the average crystallite size also increased to 24.3, 30.4, and 47.2 nm, respectively. The ZnO synthesized at temperatures of 500 °C, 600 °C, and 700 °C exhibits higher electrocatalytic activity toward the hydrogen evolution reaction (HER) compared to both the ZnO synthesized at 800 °C and commercial ZnO. This enhanced performance can be primarily attributed to the nanosized ZnO particles, which provide a substantial surface area, high accessibility of active sites, and fast charge transfer kinetics. In terms of photocatalytic activity, all the samples show HER improvement under the UV light irradiation, attributed to the generation of photoexcited charge carriers. The ZnO synthesized at 800 °C and the commercial ZnO exhibit greater enhancements in photocatalytic activity compared to the other samples. This implies that larger solid particles with fewer nanopores result in a greater exposed surface area for UV-light absorption. The hierarchically structured ZnO nanoparticles demonstrate promising electrocatalytic and photocatalytic activities, as well as stability, opening up potential applications in various fields, including energy conversion and environmental remediation.

In-situ fabrication of bimetallic FeCo2O4-FeCo2S4 heterostructure for high-efficient alkaline freshwater/seawater electrolysis

Rational construction of bifunctional electrocatalysts with long-term stability and high electrocatalytic activity is of great importance, but it is challenging to obtain highly efficient non-precious metal-based catalysts for overall seawater electrolysis. Herein, a nickel foam (NF) self-supporting CoFe-layered double hydroxide (CoFe-LDH/NF) was directly converted into FeCo2O4-FeCo2S4 heterostructure via hydrothermal method in 50 mM Na2S solution, instead of FeCo2O4@FeCo2S4 core-shell structure. The FeCo2O4-FeCo2S4 heterojunction shows nanosheets structure with rough surface (the thickness of ∼ 198.9 nm), which provides rich oxide/sulfide interfaces, high electrochemical active area, a large number of active sites, as well as fast charge and mass transfer. In 1.0 M KOH solution, 1.0 M KOH + 0.5 M NaCl, and alkaline natural seawater, the FeCo2O4-FeCo2S4 heterojunction exhibits eminently electrocatalytic performance, with overpotentials of η-100 = 225 mV, η-100 = 233 mV, and η-100 = 238 mV for OER, as well as η-100 = 271 mV, η-100 = 273 mV, and η-100 = 277 mV for HER, respectively. Furthermore, self-supporting FeCo2O4-FeCo2S4 electrode (FeCo2O4-FeCo2S4/NF) as the cathode and anode of an electrolyzer exhibits a lower cell voltage of E-100 = 1.75 V in alkaline seawater than those of FeCo2S4/NF (1.77 V), CoFe-LDH/NF (1.87 V), and FeCo2O4/NF (1.91 V). Specifically, FeCo2O4-FeCo2S4 electrolyzer can stably produce hydrogen for over 48 h in alkaline freshwater/seawater electrolyte. These outstanding electrocatalytic performances and corrosion resistance to salty-water can be attributed to the surface reconstruction behavior of the FeCo2O4-FeCo2S4/NF catalyst during OER, which leads to the in-situ formation of metal oxyhydroxides. In particular, the FeCo2O4-FeCo2S4 heterojunction is also very competitive among most state-of-the-art non-noble metal-based catalysts, whether in KOH or alkaline salty-water electrolytes.

Multipath charge transfer in Cu-BTC@CuS@CeO2 double p-n heterojunction hollow octahedrons for enhanced photocatalytic amine oxidation

Hollow heterostructured catalysts have been widely investigated and applied in photocatalytic organic reactions. However, achieving hybrid catalysts with optimized hollow structure and controllable components is still a challenge. Herein, Cu-BTC@CuS@CeO2 ternary heterostructure hollow octahedrons were designed and prepared using a copper-based metal–organic framework (Cu-BTC) as both copper source and template. A thin CeO2 nanolayer was first formed and covered on the prepared Cu-BTC octahedron surface through a hydrothermal process. In the meanwhile, the Cu-BTC octahedrons were controllably etched in this hydrothermal process, leading to the formation of Cu-BTC@CeO2 hollow octahedron. The following sulfidation reaction produced Cu-BTC@CuS@CeO2 double p-n heterojunction hollow octahedrons. Benefiting from the novel hollow octahedron double p-n heterojunctions, excellent visible-near infrared light absorption, and fast charge transfer and separation, the obtained Cu-BTC@CuS@CeO2 hollow octahedron hybrid catalyst exhibited a significantly higher photocatalytic activity toward the oxidative coupling of amines to imines at room temperature under visible-near infrared light irradiation compared to the control single component catalysts (Cu-BTC, CeO2, and CuS) and binary hybrid catalysts (Cu-BTC@CeO2, Cu-BTC@CuS, and CuS@CeO2). The enhanced charge transfer at the double p-n heterojunction was discussed. Meanwhile, the photocatalytic oxidation products and reaction mechanism were investigated by surface-enhanced Raman spectroscopy, gas chromatography-mass spectrometry, and pyridine adsorption FT-IR spectroscopy. This work presents a promising strategy for the design of multi-component hollow heterostructure catalysts.

Encapsulating flower-like MoS2 nanosheets into interlayer of nitrogen-doped graphene for high-performance lithium-ion storage

Layered molybdenum disulfide (MoS2) is a promising anode material for lithium-ion storage and its coupling with graphene can further improve the specific capacity and cycling stability. In this work, a feasible polyacrylamide (PAM)-assisted approach to prepare the flower-like MoS2 nanosheets encapsulated by nitrogen-doped graphene (FL-MoS2/N-G) is proposed. The PAM is taken as the directing agent for the layered assembly of graphene and further confined growth of FL-MoS2 in the interlayers of the graphene. The unique encapsulation construction of MoS2 and N-doped graphene leads to the high loading of active species and stabilized structural integrity after the continuous Li+ ion intercalations. Theoretical simulation results reveal that the MoS2 nanosheets coupled with N-doped graphene can accelerate the charge transfer process and create extra lithiation sites with decreased diffusion resistance of Li+ ions. As the anode material in lithium-ion batteries (LIBs), the target FL-MoS2/N-G composite exhibits a high reversible capacity of about 1202 mAh g−1 at 0.2 A g−1 and it can remain 835 mAh g−1 even at 5 A g−1, highlighting an excellent rate capacity. Additionally, the FL-MoS2/N-G anode is also capable of delivering a long-term cycling performance with a capacity retention of about 78% after 800 cycles. Furthermore, benefiting from the fast charge transfer process of the FL-MoS2/N-G dominated by surface capacitive behavior, the lithium-ion hybrid capacitor with good electrochemical performance was fabricated to brighten its practical application prospect. The current work presents a new insight into the fabrication of high-loading MoS2/N-doped graphene composites with unique nanostructures for high-performance lithium-ion storage.

Preparation of carbon sponge loaded NiPt dual-metal single atom as self-supporting electrode based on inkjet printing technology for efficient hydrogen evolution

Hitherto, Pt-based catalysts still occupy a dominant position in hydrogen evolution reaction (HER), but high cost greatly restricts their applications. Dual metal-atom catalysts (DACs) break the limitation of symmetrical charge distribution at single atomic sites, leading to the synergistic effect to reduce adsorption energies of reaction intermediates by optimized electronic structure. Herein, ZIF-8 derived strategy by inkjet printing is proposed to prepare NiPt dual-metal single atom in situ on porous carbon sponges (NiPt/CMS) as HER self-supporting electrodes. Inkjet printing is helpful to avoid aggregation of nanoparticles, so that resulting in high atomic sites density of the self-supporting electrode. Based on this, the interaction between Ni and Pt atoms of NiPt/CMS catalyst results in faster charge transfer and moderate binding with intermediates, promoting the catalytic activity of HER reaction is improved. As a result, overpotentials of 66 mV in acidic media and 67 mV in alkaline media at the current density of 10 mA cm−2 are reported for NiPt/CMS, highlighting the dual-metal single atom effect. This work provides inspiration for multiple active sites in SACs.

Efficient hybrid capacitive deionization with MnO2/g-C3N4 heterostructure: Enhancing Mn dz2 electron occupancy by interfacial electron bridge for fast charge transfer

While MnO2 has been identified as a potent agent in the desalination process, its efficacy is significantly impeded by its inherent poor electrical conductivity and substantial ion diffusion barriers. By orchestrating an interfacial electron bridge within the MnO2/g-C3N4 heterostructure, reinforced through Npz-Mndz2 orbital hybridization, we have managed to significantly boost both SAC and SAR in the HCDI process. The reinforced Npz-Mndz2 orbital hybridization triggers a substantial electron transition from g-C3N4 to MnO2, culminating in a high Mn dz2 electron occupancy. Further analysis reveals the formation of a MnN chemical bond at the MnO2/g-C3N4 interface, operating as an essential electron transfer bridge from g-C3N4 to MnO2. This process concurrently initiates a rise in the Mn dz2 orbital energy level, equipping the Mn dz2 electron with superior redox activity. With these enhancements, the manufactured MnO2/g-C3N4 exhibits exemplary performance, boasting an improved SAC of 68 mg g−1 and SAR of 3.6 mg g−1 min−1 with a decreased energy consumption of 0.7224 kWh kg−1 at 1.2 V. This innovative work offers an unconventional roadmap for activating electron redox activity and thereby accelerating charge transfer in transition metal oxides.

Defect-engineered composite with ammonium vanadate and 1T-MoS2 for superior aqueous zinc-ion battery applications

Aqueous zinc-ion batteries (AZIBs) are competitive energy-storage systems owing to their high ionic conductivity, safety, low cost, and eco-friendliness. Vanadium-based oxides have gained research interest as cathode materials for AZIBs because of their high capacities derived from their multivalent states and layered structures. However, vanadium-based oxides continue to exhibit poor performance as electrodes owing to critical issues, such as structural collapse, cation trapping, and poor electrical conductivity, which limit their practical application. Defect-engineered composite cathode materials consisting of (NH4)2V6O16·1.5H2O (NVO) nanorods and metallic 1T-MoS2 nanosheets were fabricated using a sonochemical method. NH4+ and H2O were co-intercalated into the NVO interlayer and served as pillars for stabilizing the layered structure. The 1T-MoS2 nanosheets promote fast charge transfer by providing conductive networks to the NVO. Furthermore, the oxygen defects in the NVO lattice weaken the electrostatic attraction between the inserted Zn2+ cations and the lattice oxygen layers, facilitating reversible Zn2+ (de)intercalation during charging–discharging. Consequently, the Od-NVO/Oi-MoS2 electrode exhibited a high capacity of 370.5 mAh/g at a current density of 0.2 A/g. In addition, it exhibited a high capacity of 141 mAh/g and maintained 92.5% of its initial capacity after 2000 cycles at 10 A/g.

Efficient structure tuning over the defective modulated zirconium metal organic framework with active coordinate surface for photocatalyst CO2 reduction

Structure engineering of zirconium-based metal organic frameworks (MOFs) aims to develop efficient catalysts for transforming intermittent renewable energy into value-added chemical fuels. In order to have a deeper understanding of industrial scaling, it is vital to ascertain the favourable operational parameters that are necessary for projecting at the atomic level. The proposed paradigm provides a robust basis for the efficient design of MOFs based heterogeneous photocatalysts. In this study, set of defective MOF (D-NUiO66) was effectively produced using a modular acidic method. Afterwards, the D-NUiO66 was combined with CeO2 to form the D-CeNUiO66 heterojunction for the purpose of carbon dioxide reduction. The morphological aspect of the composite investigation suggested that D-CeNUiO66 had a mesoporous structure with favourable adsorption properties. The optimized D-CeNUiO66 photocatalyst showed the high activity for the reduction of CO2 to CO, with a rate of 38.6 µmolg−1h−1 and demonstrated remarkable repeatability in terms of CO production. The incorporation of defect sites in the D-NUiO66 enhanced the light response to visible light, resulting in reduced band gap of 2.9 eV. The photoelectrochemical tests indicated that the introduction of defects in the UiO66 and coupling CeO2 in the D-CeNUiO66 composite induced fast charge transfer, therefore suppressing the charge recombination rate. This study provides valuable insights into the use of defective engineering and heterojunction approaches to metal–organic frameworks for photocatalytic applications.

Boosted sodium ion storage performance in MnO2: Understanding the bond angle-mediated orbital overlap in MnO6 units for fast charge transfer

Symmetric six oxygen-coordinated Mn structural units (MnO6) in MnO2 with small Mn–O orbital overlap hamper electron transfer rates during energy storage. Herein, we report a novel bond angle modulation strategy to manipulate Mn–O orbital overlap in MnO2 through the construction of Mn vacancies (MnO2-VMn), aiming at expediting electron transfer, and thus enhancing energy storage performance. Both experimental and theoretical results disclose that the amplification of Mn–O–Mn bond angles exclusively augments the Mn (dx2-y2)-O (py) orbital overlap and triggers the electron redistribution in MnO2-VMn, inducing an augmented Mn dx2-y2 electron occupation. This heightened presence of active electrons in the Mn dx2-y2 orbital paves the way for accelerating electron transfer and ion transfer in MnO2-VMn. Notably, MnO2-VMn delivers an improved specific capacitance of 425 F g−1 at 1 A g−1 and a superior rate capacity of 265 F g−1 at 20 A g−1. Furthermore, an asymmetric supercapacitor (MnO2-VMn//AC ASC) was fabricated, exhibiting a high energy density of 64.3 Wh kg−1 at a power density of 1000 W kg−1. Furthermore, theoretical insights uncover the profound implications of metal–oxygen–metal bond angle regulation on interatomic orbital overlap modulation. These revelations illuminate pathways for the design of advanced energy storage materials.

Phosphorus-doped molybdenum disulfide as counter electrode catalyst for efficient bifacial dye-sensitized solar cells

MoS2 is a promising counter electrode material for dye-sensitized solar cell owing to its optical and electrical properties and two-dimensional layered structure. However, it still suffers from minimal conductivity, poor charge transport and less active sites. The present study offers a promising method for enhancing catalytic and fast charge transfer in MoS2 through heteroatom doping of phosphorus. A facile one-step hydrothermal treatment was acquired to do the phosphorus doping. The spin-coated P-doped MoS2 (MSP2) counter electrode (CE) shows a superior power conversion efficiency of 7.93% for front illumination and 5.34% for rear illumination, outperforming Pt-based (7.41% and 5.75%) CE. Thus, phosphorous incorporation increases the number of active sites and improves the catalytic property of the material. The P-doped MoS2 (MSP2) CE film also shows high transmittance, making it a suitable choice for bifacial type of solar cell.

Exploration of Bifunctionality in Mn, Co Codoped CuO Nanoflakes for Overall Water Splitting

Herein, bimetal (Mn, Co) codoping on a CuO host is aimed at enhancing oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activity. Codoping of Mn and Co on CuO to enhance bifunctional action in electrochemical water splitting has not yet been investigated to the best of our knowledge. Literatures are focused on unary Mn-doped CuO or Co-doped CuO nanostructures. Mn, Co codoped CuO through an easy chemical coprecipitation method has been successfully attempted and is more beneficial which is the novelty of the present work. Defect-enriched ample active sites (Mn2+/Mn3+ and Co2+/Co3+) along with Cu2+ in the host CuO achieved high current density (100 mA/cm2) in OER and HER with low overpotential such as 468 mV and 271 mV, respectively. Faster charge transfer and diffusion ability was stimulated by the bimetal codoping CuO. Reasonable Tafel plot values (OER: 199 mV/dec, and HER: 21 mV/dec) with improved water-splitting reaction kinetics were achieved for the Mn, Co codoped CuO nanoflakes. The double-layer capacitance ( C dl ) value of 27.5 mF/cm2 for Mn, Co codoped CuO nanoflakes was achieved. Similarly, the increasing order of an electrochemically active surface area (EASA) was exhibited by the consequent addition of bimetal doping on CuO, denoted as Mn , Co / CuO > Co / CuO > Mn / CuO > CuO . The evidence shows that the codoping strategy could facilitate rapid reaction kinetics to develop overall water splitting. The charge transfer resistances ( R ct ) of 3.6 Ω and 1.2 Ω for the Mn, Co codoped CuO nanostructure corresponding to the OER and HER, respectively, were reported. The long-term stability over 16 h with negligible loss was reported for both the OER and the HER performance. Thus, this work contributes to better insight and analysis of the successful codoping of bimetal elements in earth-abundant electrocatalysts to enhance and make practical the electrocatalytic water-splitting activity.