Large Potential Window Research Articles

Engineering single-atomic Ni sites stabilized with adjacent spinel nanoparticles to boost CO2 electroreduction

Single-atom catalysts show great potential in the electrochemical CO2 reduction reaction (CO2RR), but face significant challenges in accelerating reaction kinetics. Herein, we develop a three-dimensional heterostructured MgAl2O4/Ni-N-C catalyst via a facile pyrolysis strategy, featuring abundant atomically dispersed Ni sites and ∼14 nm MgAl2O4 nanoparticles. The MgAl2O4 with rich oxygen vacancies is crucial for stabilizing Ni atoms and promoting CO2 activation, thereby contributing to an excellent selectivity of nearly 100 % and good stability for CO production. The CO Faraday efficiency remains > 90 % within a large potential window (−0.57 to −0.97 V vs. RHE), and achieves the maximum of 98.7 % at −0.82 V. Theoretical calculations reveal that MgAl2O4 introduction can modulate the electron structure of Ni atoms, and accelerate the formation of *COOH intermediate, thus boosting CO2RR performance. This research provides a novel approach for the design of high-efficiency single-atom catalysts for CO2 conversion.

Unexpected bell-shaped double layer capacitance promoted by nitrate anions at a-CNx / aqueous electrolyte interface and simulated with the lattice-gas model

Amorphous carbon nitride thin fims, a-CNx, are potentially low cost candidates for electrochemical nitrate treatment by comparison to boron doped diamond electrodes. In aqueous media, a-CNx electrodes are characterized by a large potential window and, in acidic pH solutions, no surface charge capacitive contribution. In perchloric acid at pH 1, nitrate reduction occurs at the negative limit of a potential domain without any significant redox reaction over almost 1 Volt. In this domain, in the presence of a nitrate salt, a bell-shaped behaviour was observed for the interfacial capacitance. Differences were evidenced according to the solvation state of the cations (Na+, K+, Li+, Cs+, (CH3)4N+, (C2H5)4N+), depending on the cation size. Experimental capacitance data were simulated by using the phenomenological theory developed by Kornyshev in the case of ionic liquids. A good agreement was obtained assuming a compact layer in series with the highly structured diffuse layer and taking into account the short-range ion-ion interactions. Thus, at the a-CNx/aqueous electrolyte interface, nitrate anions are engaged into strong anion-cation interactions (ion pairing) especially with small sized cations, leading to nitrate anion trapping in the multilayered interfacial region with a possible negative effect on the nitrate ions electroreduction.

Effect of Functionalized Carbon Nanotubes and Graphene Oxide Nanoribbons on the Supercapacitive Behavior of Zr-Based Metal-Organic Frameworks in Acid Media

Metal-organic frameworks (MOFs) as a kind of crystalline porous materials have attracted much attention due to their high surface area and high electrochemical performance as electrode materials in supercapacitors 1. Recently, there has been a lot of interest in functionalized multiwalled carbon nanotubes (F-MWCNTs) based materials and especially graphene oxide nanoribbons (GONRs), which have unusual characteristics of ultrathin two-dimensional structures and, as promising materials for supercapacitors and other electrochemical energy storage devices. The F-MWCNTs and GONRs' high electrical conductivity, highly changeable surface area, strong chemical stability, excellent mechanical behavior, and capacity to modify attributes for the desired application are behind the reasons for choosing to make a composite of these materials with Zr-MOF 2.In this work, Zr-MOF was synthesized using the solvothermal method 3, MWCNTs were functionalized using acid washing (3 M H2SO4: 1 M HNO3), and GONRs were fabricated using the oxidative unzipping method 4. The Zr-MOF/F-MWCNTs and Zr-MOF/GONRs composites were prepared through physical mixing. The physical and chemical structures of the synthesized Zr-MOF, F-MWCNTs, and GONRs were evaluated using XRD, SEM, TEM, FT-IR, Raman spectroscopy, and XPS. The supercapactive behavior of the prepared composites was evaluated in comparison to their components (Zr-MOF, F-MWCNTs, and GONRs) in 1M H2SO4 utilizing various evaluation systems (three and two-electrode systems). Zr-MOFs showed a high specific capacitance (248 F/g at 1 A/g), making it a promising supercapacitor electrode material. That performance is dramatically improved by the addition of the nanocarbon materials (F-MWCNTs and GONRs). Zr-MOF-GONRs showed the highest specific capacitance (448 F/g at 1 A/g), with a large potential window (1.7 V) in the three-electrode system extended to (2V) in the two-electrode system, and good stability over 10,000 cycles at a high current density of 10 A/g. Reference: (1) Tan, Y.; Zhang, W.; Gao, Y.; Wu, J.; Tang, B. Facile Synthesis and Supercapacitive Properties of Zr-Metal Organic Frameworks (UiO-66). RSC Adv. 2015, 5 (23), 17601–17605. https://doi.org/10.1039/c4ra11896k.(2) Shrivastav, V.; Sundriyal, S.; Tiwari, U. K.; Kim, K. H.; Deep, A. Metal-Organic Framework Derived Zirconium Oxide/Carbon Composite as an Improved Supercapacitor Electrode. Energy 2021, 235, 121351. https://doi.org/10.1016/j.energy.2021.121351.(3) Abdelhamid, H. N. UiO-66 as a Catalyst for Hydrogen Production: Via the Hydrolysis of Sodium Borohydride. Dalton Trans. 2020, 49 (31), 10851–10857. https://doi.org/10.1039/d0dt01688h.(4) Kosynkin, D. V.; Higginbotham, A. L.; Sinitskii, A.; Lomeda, J. R.; Dimiev, A.; Price, B. K.; Tour, J. M. Longitudinal Unzipping of Carbon Nanotubes to Form Graphene Nanoribbons. Nature 2009, 458 (7240), 872–876. https://doi.org/10.1038/nature07872.

Investigation of the Activity and Stability of Manganese-Based Electrocatalysts for the Electrochemical Oxidation of Water and Small Organic Molecules in Acidic Electrolyte

Water electrolysis is a crucial process for hydrogen production, providing a clean and sustainable method for H2 production. Iridium-based catalysts are particularly effective in promoting the oxygen evolution reaction (OER) that takes place at the anode of electrolyzers. The unique properties of iridium make it well-suited for this purpose, but its high cost becomes a bottleneck in making water electrolysis economically viable on a large scale. Manganese-based electrocatalysts have emerged as promising candidates for the OER, mainly due to their earth abundance, low toxicity, and activity. It has been shown that manganese oxide can operate stably in acid, in a restricted potential window, where the formation of permanganate ions is avoided. Thus, for practical application, the stability must be improved, so a larger potential window can be employed. To address this challenge, some approaches have emerged from combining a catalytically active, but instable oxide, with the one that is stable, but inactive for the OER. In the presentation, we will show the results of activity, stability, and faradaic efficiency (FE) for O2 formation for water electro-oxidation on manganese oxide, and on manganese oxide combined with antimony, tin, titanium, niobium, and silicon oxide. The faradaic efficiencies, determined via EC-MS (Electrochemistry coupled to mass spectrometry) measurements revealed that manganese antimonate and pure manganese oxide have the highest values for O2 formation, with the former presenting higher stability at high overpotentials. We will discuss the obtained trends in stability and FEs for the other synthesized oxides. Additionally, for these two most efficient electrocatalysts, EC-MS measurements were conducted for the electrochemical oxidation of some small organic molecules, such as formic acid, methanol, ethanol, and ethylene glycol (electrochemical reforming for H2 production). The results showed that the selectivity for the electro-oxidation of water and/or of the organic molecule (monitoring the formation of CO2) strongly depends on the catalyst composition and on the number of carbon atoms of the molecule. We will further discuss, in the presentation, the factors that govern the selectivity and stability for each case. The obtained results of this study may be helpful for developing more efficient, selective and, mainly, more stable earth-abundant electrocatalysts for electrolyzers.

(Invited) Electrochemistry of CdSe Quantum Dots in Organic Solvents. from Stochastic Electrochemistry to Film Behavior

We present our electrochemistry results of CdSe quantum dots in two organic solvents: neat methanol and acetonitrile. In MeOH, the quantum dots (QDs) can be detected through stochastic collisions; that is, as agglomerates of QDs collide with an electrode surface, the photocurrent changes as a result of the CdSe entities that collide with the electrode surface.1 The experiment presented here uses Pt ultramicroelectrodes (UME), that is, electrodes with a diameter of 25 μm or less. Our results show that the CdSe can accumulate on the surface of the electrode, and the technique provides a high degree of control. By controlling the time the electrode collects QDs, one can control the amount of CdSe that accumulates at the electrode surface. After collecting CdSe on the surface, we perform cyclic voltammetry experiments to confirm that the electrode surface has changed. In acetonitrile (MeCN), we can perform CVs over large potential windows to study the electrochemistry of the deposited CdSe. The electrochemical response of the deposited CdSe resembles that of a film, although the surface has sub-monolayer coverages, as will be discussed from the images of scanning electron microscopy (SEM).Figure 1 shows an example of a LSV in a region of interest where the current due to the CdSe significantly deviates from the background current. The LSV was run in the dark, so the current in the figure is a function of the density of states in the CdSe structures. It is also a function of the reversibility of the CV, i.e., mainly of the scan rate of the experiment. After the CV experiments, the Pt UME can be imaged in the SEM to correlate the electrochemical results with the CdSe deposited on the electrode surface. We will discuss our findings in terms of the results in the literature on CdSe electrochemistry (e.g., refs 2-5). References. (1) Subedi, P.; Parajuli, S.; Alpuche-Aviles, M. A., "Single Entity Behavior of CdSe Quantum Dot Aggregates During Photoelectrochemical Detection", Frontiers in Chemistry 9 (2021) DOI: 10.3389/fchem.2021.733642(2) Kohl, P. A.; Bard, A. J., "Semiconductor electrodes. 13. Characterization and behavior of n-type zinc oxide, cadmium sulfide, and gallium phosphide electrodes in acetonitrile solutions", Journal of the American Chemical Society 99, 7531-7539 (1977) DOI: 10.1021/ja00465a023(3) Hines, M. A.; Guyot-Sionnest, P., "Synthesis and characterization of strongly luminescing ZnS-capped CdSe nanocrystals", The Journal of Physical Chemistry 100, 468-471 (1996) DOI: 10.1021/jp9530562(4) Zhang, J. Z., "Interfacial Charge Carrier Dynamics of Colloidal Semiconductor Nanoparticles", The Journal of Physical Chemistry B 104, 7239-7253 (2000) DOI: 10.1021/jp000594s(5) Myung, N.; Ding, Z.; Bard, A. J., "Electrogenerated chemiluminescence of CdSe nanocrystals", Nano Letters 2, 1315-1319 (2002) Figure 1

Photoelectrochemical conversion for ion-selective electrodes based on CdS semiconductor film

BackgroundThis study presents a novel photoelectrochemical (PEC) conversion method for ion-selective electrodes (ISEs) based on CdS semiconductor film. The motivation stems from the need to enhance the sensitivity and precision of ISEs for various analytical applications. ResultsWe synthesized CdS film on FTO conductive glass via a hydrothermal method and utilized this electrode as the working electrode. Under visible light irradiation, CdS generated photocurrent that is proportional to its applied voltage within a large potential window of ∼0.80 V. Ascorbic acid (AA) effectively inhibited electron-hole complexation, enhancing photocurrent stability. Potential modulation from ISEs acting as the reference electrode further regulated photocurrent generation, demonstrating excellent sensitivity and linearity for a wide range of ion concentrations. The method was validated by detecting serum calcium levels, showing agreement with traditional ISEs potentiometry and ICP-OES methods. SignificanceThis photoelectrochemical conversion strategy offers a promising approach for sensitive and accurate ion detection, with potential applications in clinical diagnostics and environmental monitoring.

High-performance positive electrode material of MXene/FeNi2S4 nanocomposite for flexible supercapacitor with large potential window

Developing heterostructured nanomaterials with abundant active sites and excellent electronic conductivity is essential to enhance the electrochemical activity of supercapacitors. Herein, MXene/FeNi2S4 composites, as a high-performance electrode material for the flexible supercapacitor, were fabricated using a simple probe sonication method. The formation of a 3D architecture can create abundant electrochemical active sites, promoting the charge transfer as well as the redox reactions. Accordingly, a supercapacitor electrode based on MXene/FeNi2S4 exhibited excellent electrochemical performances, with a high specific capacitance of 673 F/g at 1 A/g. When MXene/FeNi2S4 was used as the electrode material of an asymmetric supercapacitor, the device showed an outstanding specific capacitance of 141 F/g at 1 A/g in a large potential window of 1.8 V. Up to 90 % of this high specific capacitance was retained after 2000 charge–discharge cycles. Furthermore, the device displayed high values of both energy density (63.37 Wh/kg) and power density (900.98 W/kg). The device also exhibited stable electrochemical performances under high flex at the bending angle of 135°. The exceptional electrochemical performances of MXene/FeNi2S4 highlight its great potential as an excellent electrode material for the next generation of flexible energy storage devices.

Single-step, in-situ fabrication of flower-like NiCuMn hybrid oxyhydroxide electrodes for enhanced supercapacitor performance

The rational design of highly active and low-cost electrode material is very promising for energy storage applications. The development of supercapacitors with high energy/power density is an imperative and challenging research objective. Herein, we report a highly facile synthesis approach for developing unique nano-porous hybrid NiCuMn oxyhydroxide architecture with remarkable electrochemical energy storage characteristics. The process involves dealloying of Ni15Cu15Mn70 alloy in an oxygen rich environment, resulting in a uniform 3-dimensional flower like morphology. The dealloyed electrode demonstrates ultra-high specific capacitance of 4110 F cm−3 at a high current density of 20 mA cm−2. A symmetric device exhibits a high volumetric capacitance of 365 F cm−3 at a current density of 10 mA cm−2 with a large potential window of 1.7 V. Even at very high-power density of 850 W l−1, the device exhibits a high energy density of 146 Wh l−1 along with remarkable cyclic stability of 95.4% after 10 000 cycles. The superior performance of nano-porous hybrid NiCuMn oxyhydroxide architecture was attributed to its unique microstructure that provides high surface area, and marginal internal resistance ensuring rapid charge transport.

Boosting electrochemical energy storage properties of SrGd2O4 through Yb3+ and Tm3+ rare earth ion doping

Electrochemical supercapacitors represent advanced energy storage devices that excel in the swift storage and delivery of electrical energy, effectively bridging the gap between conventional capacitors and batteries. The present work, aimed to investigate charge storage properties of SrGd2O4 and rare earth ions Yb3+ and Tm3+ doped in SrGd2O4. Both materials were prepared via simple sol-gel synthesis and characterized by XRD, XPS, and FE-SEM with EDS. Characterization confirmed the presence of Tm3+ and Yb3+ in the SrGd2O4 matrix with a uniform distribution of elements. The charge storage behavior of pure SrGd2O4 and SrGd2O4:Yb4Tm1 in various electrolytes was thoroughly explored. Large electrochemical potential windows were shown by both electrode materials in aqueous 6 M KOH (1.7 V), which is essential for supercapacitors to achieve high specific energy. Furthermore, SrGd2O4:Yb4Tm1 demonstrated a substantially more pronounced charge storage effect in 6 M KOH electrolyte, with almost double times higher specific capacitance values compared with an un-doped SrGd2O4 sample. The main impact on the electrochemical window had matrix SrGd2O4, while the main impact on specific capacitance had rear earth dopants (Yb3+ and Tm3+). Improved charge storage characteristics of SrGd2O4:Yb4Tm1 were also evident through a notable reduction in overall resistance observed in electrochemical impedance spectroscopy experiments. Concerning the two-electrode GCD measurements, the SrGd2O4:Yb4Tm1 electrode in 6 M KOH showed a specific capacitance of 143 F g−1, with the specific energy of 12.5 Wh kg−1 at 0.6 A g−1. These findings demonstrate the potential of rare earth ion doping in enhancing the energy storage properties of SrGd2O4, offering promising avenues for the development of high-performance supercapacitors.

Effect of etchant gases on the structure and properties of carbon nanofibers

The utilization of plasma-enhanced chemical vapor deposition (PECVD) for carbon nanofiber (CNF) growth using NH3 as the etchant gas has been extensively documented. Notably, NH3 serves a dual role by etching excess carbon and providing N heteroatoms. Most studies neglect to address this phenomenon, despite the well-known impact of N-doping on CNF properties. Furthermore, NH3 exhibits specific interactions with C2H2—it not only etches excess carbon, but also suppresses the dissociation of C2H2. The implications of this phenomenon on CNF micro- and macroscale morphology have not been comprehensively investigated. To elucidate the influence of etchant gases on CNF structure and properties, we fabricated two types of CNFs - N-doped CNFs (N-CNF) and undoped CNFs (U-CNF). Both were grown on identical substrates using the same carbon source (C2H2) but different etchants (NH3 and H2). Their microstructure and surface chemistry were analyzed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Electrochemical properties were investigated using cyclic voltammetry (CV). U-CNFs were found to have a larger population density and a more disordered structure than N-CNFs. N-doping was confirmed in N-CNFs using XPS analysis, which also revealed differences in relative amounts of sp2 C and O functional groups. U-CNFs exhibited distinct electrochemical properties, including smaller pseudocapacitance, larger potential window, slower outer sphere redox (OSR) kinetics, and diminished dopamine sensitivity. Electrochemical differences were rationalized based on CNF structure and surface chemistry, which, in turn, were attributed to how different etchant gases influence the PECVD process.

Platinum and Palladium Nanoparticles on Boron-Doped Diamond for the Electrochemical Detection of Hydrogen Peroxide: A Comparison Study

Neurodegenerative diseases such as Alzheimer’s and traumatic brain injury currently lacks a reliable diagnosis and treatment. This is, in part, due to knowledge gaps in the understanding of the mechanisms of brain injury. Hydrogen peroxide (H2O2) and other reactive oxygen and nitrogen species (ROS/RNS) are typical byproducts of oxygen metabolism and part of the inflammatory response cascades. Any disruptions in the uptake of ROS/RNS over an extended period of time can lead to oxidative stress, further adding to the neurodegeneration. While there are several modes of detection for ROS/RNS like H2O2, one of the major drawbacks is the lack of real-time detection. Electrochemical techniques offer real-time detection, are cheap, and easy to miniaturize. Carbon-based electrodes are particularly useful in electrochemical detection due to their ability to be adapted to different measurement systems. For neurochemical detection, carbon-fiber microelectrodes are most common but tend to foul with long-term exposure in a biological environment. Novel materials like boron-doped diamond (BDD) can mitigate this issue due to its general robustness and chemical inertness while also exhibiting small capacitive current, enhanced surface roughness, and a large potential window. As with other carbon-based electrodes, BDD can be modified to increase sensitivity towards a specific analyte like H2O2. In this work, we performed a comprehensive study of BDD electrodes modified with platinum (Pt) and palladium (Pd) nanoparticles for the detection of H2O2. The modification involves a 2-step wet chemical synthesis procedure directly onto the electrode surface. We look to expand the modification process not only to novel electrode materials, but also to metals that have not been used for this purpose previously. We optimized the modification process to find the parameters that yielded the best electrode for H2O2 detection. Several factors were investigated including the double-layer capacitance, electroactive surface area, electron transfer properties, and sensitivity to H2O2, among others. It was found that the modification yielded a 308x increase in sensitivity and a 36x decrease in limit of detection (LOD) and limit of quantification (LOQ) on Pd modified BDD when compared to bare BDD. A 256x increase in sensitivity and a 26x decrease in LOD and LOQ were observed on Pt modified BDD compared to the bare BDD. We found that the BDD modified with 1 mM Pd and electrodeposited to a 5 mC charge yielded an electrode with excellent sensitivity to H2O2 and provided a LOD and LOQ well within biological concentrations. The H2O2 measurements also exhibited excellent repeatability as the relative standard deviation (%RSD) was below 10% for all modifications. The future of this work will consist of two separate steps: 1) miniaturization of these modification methods to the microelectrode scale and 2) implementation of new materials in the modification process for H2O2 detections. In general, not only does this work further exemplify the versatility of diamond electrodes for the detection of biological H2O2, but the ease of this modification process makes the use of these electrodes fairly easy in any application where H2O2 is present.

Synthesis-Driven Computational Discovery of Organic Redoxmers for Non-Aqueous Redox Flow Batteries

Organic non-aqueous redox flow batteries (RFBs) are promising grid-scale energy storage systems for storing intermittent renewable energy in molecules. For practical applications, low-cost and stable redox active molecules (redoxmers) that display a large redox potential window and long electrochemical cycling stability are required to deliver a high-energy-density RFB with a long battery cycle life. To accelerate the discovery of redoxmer molecules, previous studies have utilized machine learning (ML) methods along with first-principles simulations. Although many ML-suggested molecules show promising electrochemical properties, they are generally difficult to synthesize because of their highly complex structure. To address this challenge, in this work, we propose a new synthesis-driven computational approach to discovering less-complex molecules with a large redox potential window that can deliver high-energy-density RFBs. Specifically, we devised an algorithm to generate an engineered molecular search space and applied a Bayesian optimization-based active learning algorithm to discover promising molecules from a large molecular search space while using a limited number of expensive density functional theory (DFT) calculations. To increase the energy density of RFBs, we focus on maximizing the redox potential window of redoxmer molecules (or cell voltage) by minimizing the reduction potential of anolyte molecules. Precisely, we studied the 2,1,3 Benzothiadiazole (BTZ) molecule, a promising anolyte (redoxmer) candidate for RFBs, and with our synthesis-driven approach discovered new BTZ-based molecules that show 15-43% smaller reduction potential than the BTZ and in principle can deliver organic RFBs with a cell voltage ≈ 3 V.

Pillaring effect of nanodiamonds and expanded voltage window of Ti3C2Tx supercapacitors in AlCl3 electrolyte

MXenes have demonstrated excellent performance as constituent materials for supercapacitor electrodes. One of the most outstanding achievements is the capacitance obtained with 2D Ti3C2Tx in H2SO4 electrolyte, which is related to the O/OH titanium surface termination redox process. However, the narrow (under 1 V) potential window of highly acidic electrolytes is a limiting feature for many applications. In this scenario, materials and electrolytes that produce high capacitance and large potential windows are highly sought after. Herein, we used nanodiamonds (NDs) to pillar the Ti3C2Tx structure and obtain superior capacitive storage in AlCl3 electrolytes. The pillaring effect prevents the restacking of MXene layers, reducing diffusion limitations and resulting in a high-rate performance with a capacitance of 235 F/g (561 F/cm3). The use of 3 M AlCl3 provided protons that contributed to the capacitance obtained and allowed an expansion of the potential window to 1.2 V, due to the lowered activity of water in the electrolyte. The results reflect the need for a proper combination of electrode architecture and electrolyte formulation while providing a direction for the exploration of more efficient, safe, and inexpensive supercapacitor devices.

In-situ crosslinking of polysiloxane electrolyte within Al2O3@SiNWs for quasi-solid-state micro-supercapacitors

Developing flexible solid-state micro-supercapacitors with large potential window is crucial for many technologies. The present study focuses on the synthesis and elaboration of quasi-solid-state (QSS) electrolytes with an electrochemical stability greater than 3.0 V based on functionalized polysiloxane. Their electrochemical behavior was studied with silicon nanowires electrodes. The polysiloxane was functionalized with both ammonium and cross-linkable functions. The nanostructured electrodes were impregnated with a mixture of ionic liquid and functionalized polysiloxane. The crosslinking of the polymer electrolyte was then performed by thermal curing directly within the nanostructured electrodes. The quasi-solid system exhibits very high stability upon galvanostatic cycling i.e. during 100 000 cycles with a cell potential of 3.0 V only a capacitance loss of 2.10−5% per cycle was registered. The performance of this QSS with safe electrolyte is remarkable.

Iontronic and electrochemical investigations of 2D tellurene in aqueous electrolytes

AbstractThe remarkable successes of graphene have sparked increasing interest in elemental two‐dimensional (2D) materials, also referred to as Xenes. Due to their chemical simplicity and appealing physiochemical properties, Xenes have shown particular potential for numerous (opto) electronic, iontronic, and energy applications. Among them, layered α‐phase tellurene has demonstrated the most promise, thanks to the recent successes in the chemical synthesis of highly crystalline 2D tellurene. However, the general electronic and electrochemical properties of tellurene in electrolyte systems remain ambiguous, hindering their further development. In this work, we studied the electrostatic gating, electrocatalysis, and electrochemical stability of tellurene in electrolyte systems. Our results show that tellurene obtained from both hydrothermal and chemical vapor deposition methods, two mainstream synthetic approaches for Xenes, demonstrates thickness‐dependent ambipolar transport with high hole mobility and stability in both aqueous electrolytes and ionic liquids. More importantly, the electrochemical properties of tellurene are investigated via the emerging on‐chip electrochemistry. Pristine tellurene demonstrates hydrogen evolution reaction with low Tafel slopes and remarkable electrochemical stability in acidic electrolytes over a large potential window. Our study provides a comprehensive understanding of the iontronic and electrochemical properties of tellurene, paving the way for the broad adoption of Xenes in sensors, synaptic devices, and electrocatalysis.

Pore filled solid electrolytes with high ionic conduction and electrochemical stability for lithium sulfur battery

High lithium (Li)-ion conductive solid electrolytes with mechanical stability are quite important in the development of long-term safe and high-performance solid-state Li-sulfur batteries (LSBs). Accordingly, we prepared a pore-filling solid electrolyte (PFSE) by introducing poly(ethylene glycol) double-grafted (poly(arylene ether sulfone) (PAES-g-2PEG), ionic liquid (IL), and ethylene carbonate (EC) into a porous polypropylene/polyethylene/polypropylene (PP/PE/PP) substrate. While the PP/PE/PP substrate provides the membrane with the mechanical strength, the PAES-g-2PEG filler provides high Li-ion conductivity due to the facile ion conduction pathway formation via percolation in the presence of IL and EC. This synergistic effect allowed the prepared PFSE membranes to exhibit both high mechanical strength of 200 MPa, thermal stability above 150 °C, and high ion conductivity of 0.604 mS cm-1 with a Li-transfer number of 0.41. Moreover, PFSE membranes also achieved a large electrochemical potential window of 4.60 V and high cyclic stability after 500 h of Li-stripping/plating. The LSB cell based on a PFSE membrane showed excellent electrochemical performance with preserving 95% of initial capacity after 200 cycles at a 0.2 C-rate.

Development of Poly(2-Methyl Thioaniline)/Vanadium Pentoxide Hybrid Electrode Material for High Performance Supercapacitor Applications

To satisfy the constantly growing demand for energy, it is crucial to design electrode materials that have high specific capacitance and excellent reversibility to be used in applications such as portable electronics, backup power supplies, smart grids, hybrid vehicles, transportation and wearable electronics fields. This report presents a novel approach to creating such materials through the electrochemical deposition of a poly(2-methyl thioaniline)/vanadium pentoxide (PMTA/V2O5) hybrid material. The hybrid material was tested as a supercapacitor electrode material by means of cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy techniques. The PMTA/V2O5 hybrid demonstrated excellent charge-storage capabilities within a large potential window (–1.0 to 1.0 V), with a specific capacitance of 698 F/g at a current density of 1 A/g for samples that had a 1 mm thickness. This value is higher than the specific capacitance of V2O5 and resulted from the organic-inorganic synergistic effect between PMTA and V2O5. Facilitated charge-transfer between the two components owing to the presence of a strong electron-donating group (-SCH3) in PMTA led to a superior electrochemical performance of the PMTA/V2O5 hybrid. This strategy can be applied to produce thin films based on PMTA/V2O5, which have the potential to serve as active electrode material in supercapacitor devices.

Nickel cobaltite nanowire arrays grown on nitrogen-doped carbon nanotube fiber fabric for high-performance flexible supercapacitors

Flexible supercapacitors have received considerable attention for their potential application in flexible electronics, but usually suffer from relatively low energy density. Developing flexible electrodes with high capacitance and constructing asymmetric supercapacitors with large potential window has been considered as the most effective approach to achieve high energy density. Here, a flexible electrode with nickel cobaltite (NiCo2O4) nanowire arrays on nitrogen (N)-doped carbon nanotube fiber fabric (denoted as CNTFF and NCNTFF, respectively) was designed and fabricated through a facile hydrothermal growth and heat treatment process. The obtained NCNTFF-NiCo2O4 delivered a high capacitance of 2430.5 mF cm−2 at 2 mA cm−2, a good rate capability of 62.1 % capacitance retention even at 100 mA cm−2 and a stable cycling performance of 85.2 % capacitance retention after 10,000 cycles. Moreover, the asymmetric supercapacitor constructed with NCNTFF-NiCo2O4 as positive electrode and activated CNTFF as negative electrode exhibited a combination of high capacitance (883.6 mF cm−2 at 2 mA cm−2), high energy density (241 μW h cm−2) and high power density (80175.1 μW cm−2). This device also had a long cycle life after 10,000 cycles and good mechanical flexibility under bending conditions. Our work provides a new perspective on constructing high-performance flexible supercapacitors for flexible electronics.

Bioderived Ionic Liquids with Alkaline Metal Ions for Transient Ionics.

Choline lactate, an ionic liquid composed of bioderived materials, offers an opportunity to develop biodegradable electrochemical devices. Although ionic liquids possess large potential windows, high conductivity, and are nonvolatile, they do not exhibit electrochemical characteristics such as intercalation pseudocapacitance, redox pseudocapacitance, and electrochromism. Herein, bioderived ionic liquids are developed, including metal ions, Li, Na, and Ca, to yield ionic liquid with electrochemical behavior. Differential scanning calorimetry results reveal that the ionic liquids remained in liquid state from 230.42 to 373.15 K. The conductivities of the ionic liquids with metal are lower than those of the pristine ionic liquid, whereas the capacitance change negligibly. A protocol of the Organization for Economic Co-operation and Development 301C modified MITI test (I) confirms that the pristine ionic liquid and ionic liquids with metal are readily biodegradable. Additionally, an ionic gel comprising the ionic liquid and poly(vinyl alcohol) is biodegradable. An electrochromic device is developed using an ionic liquid containing Li ions. The device successfully changes color at -2.5V, demonstrating the intercalation of Li ions into the WO3 crystal. The results suggest that the electrochemically active ionic liquids have potential for the development of environmentally benign devices, sustainable electronics, and bioresorbable/implantable devices.

Cu/CdCO3 catalysts for efficient electrochemical CO2 reduction over the wide potential window

High efficiency and low-cost catalyst-driven electrocatalytic CO2 reduction to CO production are of great significance for energy storage and development. The severe competitive hydrogen evolution reaction occurs at large negative potential window limits the achievement of the target product from CO2 at high efficiency. Here, we successfully prepared Cux/CdCO3 composite catalyst rich in interfaces, in which achieved high CO Faraday efficiency exceeded 90% in a wide potential window of 700 mV and highest value up to 97.9% at −0.90 V vs. RHE. The excellent performance can be ascribed to the positive contribution of Cux/CdCO3, which maintains a suitable high local pH value during electrochemical reduction, thus inhibiting the competitive hydrogen evolution reaction. Moreover, the compact structure between Cu and CdCO3 ensures fast electron transfer both inside catalysts and interface, thus speeding up the reaction kinetics of CO2 to CO conversion. Theoretically calculations further prove that the combination of Cu and CdCO3 provides the well-defined electronic structure for intermediates adsorption, significantly reducing the reaction barrier for the formation of CO. This work provides new insights into the design of efficient electrochemical CO2 reduction catalysts for inhibiting hydrogen evolution by adjusting the local pH effect.