Electrochemical Activity Research Articles

Influence of electrolytes on the potentiodynamic kinetics, photocurrents, and charge kinetics of (Fe) metal–organic-framework nanostructures synthesized via microwave-assisted technique

The influence of synthesis methods on Materials Institute Lavoisier (MIL) nanostructures and their photoelectrochemical activities was examined under light-ON/OFF states. Additionally, the impacts of various electrolytes on the performance of the MIL electrodes and kinetic activities of the anodes were investigated. Compared with the samples prepared using the hydrothermal technique (MFH samples), the samples synthesized using the microwave-assisted technique (MFM samples) exhibited significantly higher electrochemical activities. In the ON state, the MFM sample in a 0.1 M NaOH electrolyte showed the lowest charge-movement resistance of 154.28 Ω, which was much lower than that of the MFH sample. The MFM sample generated a significantly higher photocurrent density in the NaOH electrolyte owing to its increased number of active sites, low resistance, and reduced Tafel slopes. Thus, MFM electrodes with robust and stable nanostructures are suitable for electrochemical applications.

Donor-acceptor-donor type AIEgens based on thieno[3.4-c]pyrrole-4,6-dione: Synthesis, electropolymerization, and electrochromism.

Photoelectric functional materials with electrochemical reversible activity and fluorescence intensities have attracted significant interest due to their wide range of applications in optoelectronic devices. In this work, a series of photoresponsive and electroactive monomers based on thieno[3.4-c]pyrrole-4,6-dione (TPD) are synthesized and characterized. They possess planar geometry with smaller dihedral angles owing to the existence of a noncovalent conformation lock coming from the S atoms and the O atoms. Crystallographic, spectroscopic, and computational results reveal that the introduction of the TPD unit can endow the monomers with aggregation-induced emission (AIE), reduced energy levels, and increased electrochemical activity. The monomers were successfully polymerized through the electrochemical method, and the corresponding polymers displayed reversible electrochemical activity and stability. Moreover, polymer films based on 3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (ProE)-TPD have electrochromic properties in the near-infrared field with a high value of optical contrast ratio (∆T) of 27.1% at 1000 nm.

Facile enrichment of sulfur-modified copper nanograin boundaries for efficient CO2 electroreduction and Zn-CO2 battery

Generating formic acid/formate (HCOOH/HCOO−) through renewable electricity-powered carbon dioxide reduction reaction (CO2RR) presents an appealing prospect for realizing a carbon-neutral energy cycle. Among various catalysts, sulfur-modified copper (S-Cu) stands out as potential catalysts due to their favorable attributes of high activity and especially earth abundance. However, the development of facile and energy-efficient methods for preparing S-Cu catalysts remains a great challenge. Additionally, there is still a lack of effective strategies to optimize their performance toward CO2RR. Herein, we present a facile and energy-saving method to fabricate a novel S-Cu precursor. After electrochemical activation, the precursor is converted into an S-Cu nanostructured catalyst, featuring a substantial abundance of nanograin boundary sites. This characteristic contributes to an outstanding CO2RR performance toward HCOO−, surpassing most recently reported counterparts. In situ characterizations together with control experiments disclose that the nanograin boundaries of S-Cu catalysts favor the formation of the *OCHO intermediates, while suppressing hydrogen evolution, ultimately boosting HCOO− production. Thus, the enhanced activity stems from the enrichment of nanograin boundary sites which are expected to be a common feature of advanced catalysts to achieve high HCOO− production. Moreover, when the as-prepared S-Cu catalyst is assembled as the cathode in a Zn-CO2 battery, a power density of 1.10 mW cm−2 is achieved, along with an impressive stability exceeding 250 h. This work presents a facile approach for preparing outstanding catalysts and also sheds a new light on optimizing the performance for CO2 electroreduction to HCOO−.

Aptasensor based on gold nanostructure-decorated 2D Cu metal-organic framework nanosheets for highly sensitive and specific electrochemical lipopolysaccharide detection.

Detecting lipopolysaccharide (LPS) using electrochemical methods is significant because of theirexceptional sensitivity, simplicity, and user-friendliness. Two-dimensional metal-organic framework (2D-MOF) that merges the benefits of MOF and 2D nanostructure has exhibited remarkable performance in constructing electrochemical sensors, notably surpassing traditional 3D-MOFs. In this study, Cu[tetrakis(4-carboxylphenyl)porphyrin] (Cu-TCPP) and Cu(tetrahydroxyquinone) (Cu-THQ) 2D nanosheets were synthesized and applied on a glassy carbon electrode (GCE). The 2D-MOF nanosheets, which serve as supporting layers, exhibit improved electron transfer and electronic conductivity characteristics. Subsequently, the modified electrode was subjected to electrodeposition with Au nanostructures, resulting in the formation of Au/Cu-TCPP/GCE and Au/Cu-THQ/GCE. Notably, the Au/Cu-THQ/GCE demonstrated superior electrochemical activity because of the 2D morphology, redox ligand, dense Cu sites, and improved deposition of flower-like Au nanostructure based on Cu-THQ. The electron transfer specific surface area was increased by the improved deposition of Au nanostructures, which facilitates enriched binding of LPS aptamer and significantly improved thedetection performance of Apt/Au/Cu-THQ/GCE electrochemical aptasensor. The limit of detection for LPS reached 0.15fg/mL with a linear range of 1fg/mL - 100pg/mL. Theproposed aptasensor demonstrated the ability to detect LPS in serum samples with satisfactory accuracy, indicating significant potential for clinical diagnosis.

Electrochemistry and DFT study of galvanic interaction on the surface of monoclinic pyrrhotite (0 0 1) and galena (1 0 0)

The electrochemical interaction between galena and monoclinic pyrrhotite was investigated to examine its impact on the physical and chemical properties of the mineral micro-surface. This investigation employed techniques such as electrochemistry, metal ion stripping, X-ray photoelectron spectroscopy, and quantum chemistry. The electrochemical test results demonstrate that the galena surface in the electro-couple system exhibits a lower electrostatic potential and higher electrochemical activity compared to the monoclinic pyrrhotite surface, rendering it more susceptible to oxidation dissolution. Monoclinic pyrrhotite significantly amplifies the corrosion rate of the galena surface. Mulliken charge population calculations indicate that electrons are consistently transferred from galena to monoclinic pyrrhotite, with the number of electron transfers on the mineral surface increasing as the interaction distance decreases. The analysis of state density revealed a shift in the surface state density of galena towards lower energy levels, resulting in decreased reactivity and increased difficulty for the reagent to adsorb onto the mineral surface. Conversely, monoclinic pyrrhotite exhibited an opposite trend. The XPS test results indicate that galvanic interaction leads to the formation of hydrophilic substances, PbSxOy and Pb(OH)2, on the surface of galena. Additionally, the surface of monoclinic pyrrhotite not only adsorbs Pb2+ but also undergoes S0 formation, thereby augmenting its hydrophobic nature.

Nb-MXene as promising material for electrocatalysis in energy conversion (OER/ORR) and storage

Low-cost non-noble metal electrocatalysts are currently the focus of research and development for energy conversion and storage devices. MXenes, the newest class of two-dimensional materials, have high surface area, nanometer layer thickness, hydrophilicity and high electrical conductivity that favor their performance for electrocatalytic reactions. Herein, niobium carbide MXene (Nb-MXene) was obtained from its MAX phase by chemical synthesis and characterized regarding its morphology, structure and electrochemical activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) as well as for charge storage in different electrolytic media. The results demonstrate the good performance of Nb-MXene for storing charge (104 F g−1 at 5 mV s−1) that increased remarkably with continuous cycling in an acidic medium. Current density for oxygen evolution of ∼32.5 mA cm−2 was reached in alkaline medium. The oxygen reduction reaction in the same media was observed to proceed via 2e− mechanism with a Tafel slope of 114 mV dec−1. Therefore, Nb-MXene presents characteristics and performance of a promising material for electrocatalytic reactions.

Influence of 3D printed porous aluminum anode structure on electrochemical performance

Aluminium-air (Al-air) batteries have been considered as one of the most promising next-generation energy storage devices. In this study, we investigated the effect of structural changes in the main body of porous aluminium anode on the electrochemical performance under the constraints of the 3D printing process using both simulation and experimental methods. By analysing the simulation results under the constraint of 3D printing process, we found that the variation of the base fillet radius affects the dimensional deviation of the porous aluminium anode. As the radius of the fillet increases, the degree of warpage deformation gradually decreases. For this reason, we experimentally verified the self-corrosion rate, electrochemical and discharge properties of aluminium anodes under the same process parameters. The test results are consistent with the simulation analysis. With the increase of fillet radius, the self-corrosion rate of anode gradually decreases and the electrochemical activity gradually increases. Meanwhile, the discharge voltage was as low as 1.55 V in the periphery without rounded corners, and increased by 1.3 % and 3.2 % when the periphery radius was 1 mm and 2 mm, respectively. This research result provides a new method for other researchers to further improve the overall performance of aluminium-air batteries.

Spontaneous heterophase atomic structure engineering of NiMo(S)/NiMoP for enhanced overall electrochemical water splitting in neutral media

Hydrogen/oxygen evolution reactions catalyzed by transition metals have sluggish kinetics during prolonged water electrolysis in neutral media. Covering the surface with an amorphous protecting layer can improve the reactivity and stability of these catalysts; however, the rational design of crystalline–amorphous electrocatalysts for efficient and stable water electrolysis in neutral media has been challenging. Here, we present a unique and facile strategy for the in situ synthesis of the heterophase-structured cNiMo(S)/aNiMoP catalyst with a crystalline–amorphous phase boundary. The high-density active sites present on the surface and at the interface of the heterophase is responsible for the excellent electrochemical activity and operational stability of water electrolysis in neutral media. For the overall water splitting reaction, the cNiMo(S)/aNiMoP || cNiMo(S)/aNiMoP system displays a low cell voltage of 1.67 V to achieve a current density of 100 mA cm−2. Moreover, negligible performance degradation was observed during a continuous long-term stability test for 100 h.

Bio-Based Materials for Electrochemical Detection of Bisphenol A

Bisphenol A is a widely used endocrine disruptor known for its toxicity and prevalence in the environment. It contaminates drinking water, especially when plastic bottles are exposed to Sunlight. Rapid, on-site detection of BPA in drinking water is crucial for protecting human health and the environment. Herein, we developed an electrochemical sensor for detecting and monitoring bisphenol A in water bodies utilizing biobased materials. The device uses a biopolymeric membrane with agarose and gelified green tea tannins (GT/Agar). A sensitive part was made using this natural composite due to its high ability to attach bisphenol A to tannin monomers. Green tea tannins were purified and characterized through HPLC, FTIR, SEM, and AFM. The electrochemical activity of the GT-Agar/Au sensor is also evaluated by electrochemical impedance spectroscopy, cyclic voltammetry, square wave voltammetry and scan rate. Based on its redox signal under the optimal experimental conditions, this sensor has a detection range of 10−16 M to 10−4 M, a limit of detection of 1.52 to 10−17 M and very high selectivity. The proposed sensor successfully determined BPA levels from ultra-trace concentrations in bottled water samples, achieving satisfactory recovery rates. Compared to the results obtained using HPLC, it demonstrates high reliability.

Alginate-graft-polyacrylic acid electro-responsive hydrogels: Impact of the conducting polymer and application as hydrogen peroxide sensor

Aiming to advance in the field of soft bioelectronics interfaces, hydrogels obtained from synthetic polyacrilic acid (PAA) grafted to alginate (Alg), Alg-g-PAA, have been rendered electro-responsive by incorporating semi-interpenetrated conducting polymer (CP) chains. The three CPs considered, poly(hydroxymethyl-3,4-ethylenedioxythiophene) (PHMeEDOT), polypyrrole (PPy) and polyaniline (PAni), were incorporated either after the formation of the Alg-g-PAA hydrogel (PHMeEDOT and PAni), or in situ during its preparation (PPy). After chemical and physical characterization, the electrochemical response and cytocompatibility of Alg-g-PAA/PHMeEDOT, Alg-g-PAA/PPy and Alg-g-PAA/PAni hydrogels were evaluated by cyclic voltammetry and the MTT assay, respectively. While the transport of ions in Alg-g-PAA produces some electrochemical activity, hydrogels semi-interpenetrated with CPs exhibited a significant enhancement of the electrochemical response on account of the electronic contribution of the CP. The conducting hydrogel with the highest cytocompatibility was found to be Alg-g-PAA/PHMeEDOT, the PPy and PAni semi-intercalated hydrogels displayed some cytotoxicity due to unreacted reagents employed for the preparation of the CP component (i.e. monomer and/or oxidizing agent). Finally, the potential application of the semi-interpenetrated conducting hydrogels as biosensors for the electrochemical detection of hydrogen peroxide was explored. Alg-g-PAA/PHMeEDOT, which was more sensitive to the presence of hydrogen peroxide than the other two CP-containing hydrogels, exhibited a sensitivity of 71.9 mA/(cm2·mM) and a detection limit of 0.9 mM.

Exfoliated 2D Nanosheet-Based Conjugated Polymer Composites with P-N Heterojunction Interfaces for Highly Efficient Electrocatalytic Hydrogen Evolution.

We have achieved a significant breakthrough in the preparation and development of two-dimensional nanocomposites with P-N heterojunction interfaces as efficient cathode catalysts for electrochemical hydrogen evolution reaction (HER) and iodide oxidation reaction (IOR). P-type acid-doped polyaniline (PANI) and N-type exfoliated molybdenum disulfide (MoS2) nanosheets can form structurally stable composites due to formation of P-N heterojunction structures at their interfaces. These P-N heterojunctions facilitate charge transfer from PANI to MoS2 structures and thus significantly enhance the catalytic efficiency of MoS2 in the HER and IOR. Herein, by combining efficient sodium-functionalized chitosan-assisted MoS2 exfoliation, electropolymerization of PANI on nickel foam (NF) substrate, and electrochemical activation, controllable and scalable Na-Chitosan/MoS2/PANI/NF electrodes are successfully constructed as non-noble metal-based electrochemical catalysts. Compared to a commercial platinum/carbon (Pt/C) catalyst, the Na-Chitosan/MoS2/PANI/NF electrode exhibits significantly lower resistance and overpotential, a similar Tafel slope, and excellent catalytic stability at high current densities, demonstrating excellent catalytic performance in the HER under acidic conditions. More importantly, results obtained from proton exchange membrane fuel cell devices confirm the Na-Chitosan/MoS2/PANI/NF electrode exhibits a low turn-on voltage, high current density, and stable operation at 2 V. Thus, this system holds potential as a replacement for Pt/C with feasibility for applications in energy-related fields.

A Redox‐Active Phenothiazine‐based Pd2L4‐Type Coordination Cage and Its Isolable Crystalline Polyradical Cations

AbstractPolyradical cages are of great interest because they show very fascinating physical and chemical properties, but many challenges remain, especially for their synthesis and characterization. Herein, we present the synthesis of a polyradical cation cage 14⋅+ through post‐synthetic oxidation of a redox‐active phenothiazine‐based Pd2L4‐type coordination cage 1. It′s worth noting that 1 exhibits excellent reversible electrochemical and chemical redox activity due to the introduction of a bulky 3,5‐di‐tert‐butyl‐4‐methoxyphenyl substituent. The generation of 14⋅+ through reversible electrochemical oxidation is investigated by in situ UV/Vis‐NIR and EPR spectroelectrochemistry. Meanwhile, chemical oxidation of 1 can also produce 14⋅+ which can be reversibly reduced back to the original cage 1, and the process is monitored by EPR and NMR spectroscopies. Eventually, we succeed in the isolation and single crystal X‐ray diffraction analysis of 14⋅+, whose electronic structure and conformation are distinct to original 1. The magnetic susceptibility measurements indicate the predominantly antiferromagnetic interactions between the four phenothiazine radical cations in 14⋅+. We believe that our study including the facile synthesis methodology and in situ spectroelectrochemistry will shed some light on the synthesis and characterization of novel polyradical systems, opening more perspectives for developing functional supramolecular cages.

A Redox-Active Phenothiazine-based Pd2L4-Type Coordination Cage and Its Isolable Crystalline Polyradical Cations.

Polyradical cages are of great interest because they show very fascinating physical and chemical properties, but many challenges remain, especially for their synthesis and characterization. Herein, we present the synthesis of a polyradical cation cage 14⋅+ through post-synthetic oxidation of a redox-active phenothiazine-based Pd2L4-type coordination cage 1. It's worth noting that 1 exhibits excellent reversible electrochemical and chemical redox activity due to the introduction of a bulky 3,5-di-tert-butyl-4-methoxyphenyl substituent. The generation of 14⋅+ through reversible electrochemical oxidation is investigated by in situ UV/Vis-NIR and EPR spectroelectrochemistry. Meanwhile, chemical oxidation of 1 can also produce 14⋅+ which can be reversibly reduced back to the original cage 1, and the process is monitored by EPR and NMR spectroscopies. Eventually, we succeed in the isolation and single crystal X-ray diffraction analysis of 14⋅+, whose electronic structure and conformation are distinct to original 1. The magnetic susceptibility measurements indicate the predominantly antiferromagnetic interactions between the four phenothiazine radical cations in 14⋅+. We believe that our study including the facile synthesis methodology and in situ spectroelectrochemistry will shed some light on the synthesis and characterization of novel polyradical systems, opening more perspectives for developing functional supramolecular cages.

Hollow Octahedral Pr6O11‐Mn2O3 Heterostructures for High‐Performance Aqueous Zn‐Ion Batteries

AbstractMn‐based oxides are broadly prospected cathode materials for aqueous Zn‐ion batteries (AZIBs) due to their rich abundance, low cost, and plentiful valence states. However, the further development of Mn‐based oxides is severely restricted by the dissolution of active materials and poor structural stability. Herein, hollow octahedral Pr6O11‐Mn2O3 (denoted as PrO‐MnO) heterostructures are developed through a facile metal–organic framework‐engaged templating approach, which realizes boosted Zn ion storage performance. Pr6O11 can not only effectively suppress the dissolution of Mn to stabilize Mn2O3 but also induce interfacial charge rearrangement and promote electron/ion transfer, contributing to the improved electrochemical activity and stability of PrO‐MnO. Moreover, the rationally designed hollow nanostructure offers sufficient active sites and facilitates the reaction kinetics. As expected, the PrO‐MnO cathode exhibits excellent rate and cycling performance with a high reversible capacity of 140.8 mAh g−1 after 2000 cycles at 1 A g−1, outperforming the Mn2O3 cathode.

Regulating the zinc ion transport kinetics of Mn3O4 through copper doping towards high-capacity aqueous Zn-ion battery

High working voltage, large theoretical capacity and cheapness render Mn3O4 promising cathode candidate for aqueous zinc ion batteries (AZIBs). Unfortunately, poor electrochemical activity and bad structural stability lead to low capacity and unsatisfactory cycling performance. Herein, Mn3O4 material was fabricated through a facile precipitation reaction and divalent copper ions were introduced into the crystal framework, and ultra-small Cu-doped Mn3O4 nanocrystalline cathode materials with mixed valence states of Mn2+, Mn3+ and Mn4+ were obtained via post-calcination. The presence of Cu acts as structural stabilizer by partial substitution of Mn, as well as enhance the conductivity and reactivity of Mn3O4. Significantly, based on electrochemical investigations and ex-situ XPS characterization, a synergistic effect between copper and manganese was revealed in the Cu-doped Mn3O4, in which divalent Cu2+ can catalyze the transformation of Mn3+ and Mn4+ to divalent Mn2+, accompanied by the translation of Cu2+ to Cu0 and Cu+. Benefitting from the above advantages, the Mn3O4 cathode doped with moderate copper (abbreviated as CMO-2) delivers large discharge capacity of 352.9 mAh g−1 at 100 mA g−1, which is significantly better than Mn3O4 (only 247.8 mAh g−1). In addition, CMO-2 holds 203.3 mAh g−1 discharge capacity after 1000 cycles at 1 A g−1 with 98.6 % retention, and after 1000 cycles at 5 A g−1, it still performs decent discharge capacity of 104.2 mAh g−1. This work provides new ideas and approaches for constructing manganese-based AZIBs with long lifespan and high capacity.

Improving rate performance of FeC2O4/rGO composites on lithium storage via single-polymerization‐induced electrostatic self‐assembly

Based on the wide interlayer distance for ions diffusion, iron (II) oxalate exhibits excellent lithium storage ability. However, the local deposition of metallic nanoparticles of Fe0 leads to low electrochemical reactivity, which hinders the actual application of FeC2O4 in large current regions (>5C). To solve this problem, a strong cationic polymeric electrolyte, polyelectrolyte diallyl dimethyl ammonium (PDDA), was introduced to construct a [FeC2O4(PDDA)]+ ligand. By single-polymerization‐induced electrostatic self-assembly, the [FeC2O4(PDDA)]+ ligand was combined with the surface-charged rGO to produce a FeC2O4/rGO material. It is proved that the rGO carrier improves the interparticle conductivity, electrochemical activity and structure stability of the iron (II) oxalate particles, ensuring the stability of Li || FeC2O4/rGO battery at a rapid charging rate of 20C (8 A g−1) for more than 500 cycles (with the special capacity of 713 mAh g−1). Compared with FeC2O4 electrode, owning to high reactivity of rGO and continuously activating on the nanoscale Fe metal generated at ∼0.75 V, FeC2O4/rGO shows higher electrochemical activity of conversion reaction in the first 50 cycles and better reversibility in the rate charge–discharge test (the capacity rapidly increased to 1158.8 mAh g−1 after 20C cycles). This work reveals how the structural design of conducting and supporting the carrier can achieve fast charging for iron (II) oxalate lithium-ion batteries.

Cocos nucifera mediated green synthesis and characterization of BiOCl-Fe2O3 nanocomposite for photocatalytic dye degradation and electrochemical sensing of dopamine

In this study, BiOCl-Fe2O3 nanocomposite was synthesized by mixing 1:1 ratio of pre-prepared BiOCl and Fe2O3 in 100 mL of H2O using Cocos nucifera (coconut milk) as a green fuel through the microwave irradiation method. X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM) with, Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy(UV–vis), and photoluminescence (PL) spectroscopy analysis were used to determine the structure, morphology, and optical features of synthesised nanocomposites. The characterized composites were used to dye degradation and electrochemical activity. Synthesized BiOCl-Fe2O3were degraded methylene blue (MB) 96.2 % in 105 min irradiation of visible light. The BiOCl-Fe2O3exhibits significant catalytic activity towards dopamine(DA) under optimal conditions. Cyclic Voltammetry(CV) and Linear sweep voltammetry (LSV) with different concentrations of DA was studied. These results indicate that this BiOCl-Fe2O3 is an effective approach for the precise and reliable identification of DA signals in biological samples.

Restrained interfacial resistance Co5.47N@C derived from metal-organic frameworks for advanced Li–CO2 batteries cathodes

Lithium–carbon dioxide (Li–CO2) batteries are novel high energy density energy storage devices that can simultaneously enrich and convert CO2, but their widespread implementation is hindered by the continuous accumulation of lithium carbonate at the cathode. Herein, we developed non-precious metal cobalt-based nitride matrix composite Co[Formula: see text]N@C based on metal-organic frameworks precursor for the catalytic cathode of advanced Li–CO2 batteries. The highly stable Co[Formula: see text]N achieves favorable adsorption and catalysis of CO2 molecules by virtue of the excellent electronic structure on the surface, while the nanoscale high dispersion also effectively promotes interfacial electron transfer. As expected, the assembled Li–CO2 battery exhibits excellent electrochemical performance in the discharge capacity of 10,000 mAh g[Formula: see text] and a cycling capability of about 400 h. Further density functional theory (DFT) calculations explored the relationship between electronic structure and electrochemical activity. This work promotes the development of catalytic materials for Li–CO2 batteries cathode.

P-doped MoS2 nanosheets embedded in 3D porous carbon for electrocatalytic hydrogen evolution reaction

Due to its inherent electrochemical catalytic activity, molybdenum sulfide (MoS2) is a potential electrocatalyst for hydrogen evolution reaction (HER). However, the limited exposure of its active sites resulting from the easy stacking of nanosheets and inert basal plane hampered its optimal catalytic activity. Herein, we developed a novel facile hydrothermal method to prepare phosphorus-doped MoS2 nanosheets anchored on agar-derived 3D nitrogen-doped porous carbon (P-MoS2/NC). The synthesized P-MoS2/NC electrocatalyst possesses high HER catalytic activity with a low overpotential of 167 mV at 10 mA cm−2 and a small Tafel slope of 45 mV dec−1. The excellent performance is attributed to the unique 3D network carbon structure, which avoids the stacking of the MoS2 sheets resulting in more exposed active sites. Additionally, the P atom introduced on the surface of MoS2 sheets successfully activated the in-plane inertness. This work provides an efficient strategy for designing and preparing high-quality catalysts with enhanced electrocatalytic HER activity.

Room-temperature synthesis of VO(OH)2 as a high capacity cathode material for aqueous zinc ion batteries

The development of satisfactory cathodes plays a key role in the widespread utilization of aqueous zinc ion batteries. Cathode materials with high specific capacity and long cycling life are still urgently needed for aqueous zinc ion batteries. Herein, a new cathode material VO(OH)2 is synthesized by a facile room-temperature precipitation approach, and its electrochemical characteristics and structural evolution process are investigated. Benefiting from its intrinsic electrochemical activity, the VO(OH)2 cathode exhibits a remarkable specific capacity of 488 mAh g−1 at 0.1 A g−1, retains a high capacity of 219.1 mAh g−1 at the increased current density of 10 A g−1, and provides a maximum energy density of 439.2 Wh kg−1. In addition, when subjected to a 12,000 cycles charge/discharge test at 10 A g−1, the cathode retains a capacity of 185.8 mAh g−1, highlighting durable cycling performance. The structural evolution analysis reveals that of VO(OH)2 cathode may be in-situ transformed to an amorphous vanadium oxide V2O5-x in the first charging process, which could reversibly intercalate/deintercalate zinc ions. This research supplies a promising cathode material for aqueous zinc ion batteries and enhances understanding of vanadium oxyhydroxide in metal ion storage.