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• Carbon paper electrode shows poor mechanical stability, affecting the AORFB performance. • The mechanical robustness of carbon cloth electrode contributes to a reliable and durable AORFB performance. • Carbon cloth electrode showed high stability when used on quinone oxidation–reduction cycles. • Electrochemical active sites on the carbon cloth increase current densities and AORFB power density. • Carbon cloth electrode provides higher AORFB power density at high electrolyte flow rate. Aqueous organic redox flow batteries (AORFBs) are emerging as promising candidates for efficient energy storage in grid-scale applications. In this study, we present a comprehensive analysis comparing the performance of thermally treated carbon paper and chemically oxidized carbon cloth electrodes, which have been extensively examined for their potential suitability in AORFBs. Results indicate that carbon cloth electrodes exhibit a higher concentration of oxygenated functional groups, contributing to enhanced electrochemical kinetics and improved electrochemical stability. These attributes translate to an AORFB with 62 times higher power density when compared to paper-based electrodes used. Through repeated charge-discharge cycles utilizing the BQDS║AQS model as a representative AORFB prototype, superior performance in the carbon cloth electrodes is consistently observed. Our findings even suggest the potential for optimizing the flow rate of the electrolyte to further enhance performance. [ABSTRACT FROM AUTHOR]

Since 2020, human pharmaceuticals were included in the list of emerging contaminants from the UNESCO and their detection and elimination were incorporated in the 2030 Agenda for Sustainable Development Goal Targets. Among these, analgesic and antipyretic drugs are the most widely used drugs worldwide and, despite their advantages, unused or expired pharmaceuticals are a potential source of water pollution. Paracetamol is one of the most common drugs used for analgesic and antipyretic purposes and has been found to have a much higher concentration in water streams in many European countries. Considering that, an all-in-one paper-based 2 dimensional (2D) fluidic configuration, able to detect paracetamol, was developed in order to deal with environmental matrices without complex/expensive analytical procedures. An ad-hoc paper-based testing area, coupled with a channel was designed and wax-printed onto a porous filter paper. Successively three electrodes were screen-printed, and the whole system was applied for the detection of paracetamol in wastewaters (prior and after the filtration system) without pretreating the sample. In order to detect paracetamol with the easiest approach, the configuration of the paper-based device was optimized in terms of type of substrate used for printing, microfluidic paper strip length/width and combination of them in an integrated architecture, capable to detect paracetamol in the matrices tested in few seconds with a detection limit down to micromolar range, ca. 1 μM. The integrated device shown great promise for simple, fast, sensitive, and sustainable detection of paracetamol in its role of emerging contaminant, especially in the environmental matrices. [ABSTRACT FROM AUTHOR]

Triple-negative breast cancer (TNBC) is one of the most aggressive and lethal types of BC, affecting mostly young women and its diagnosis is difficult and requires invasive methods, such as tissue biopsy which is painful and expensive. However, nowadays liquid biopsy is emerging as a great tool for determining blood-circulating species associated to cancer and to its early diagnosis and prognosis. Among the species, the relevance of microRNAs (miRNAs) has been highlighted as promising biomarker, and miRNA-652 has been associated with TNBC as it promotes the growth and migration of cancer cells. In this work we designed and characterized a paper-based electrochemical device capable of recognizing and quantifying miRNA-652, as future tool for liquid biopsy in TNBC. The device consists of an AuNP-modified office paper-based screen-printed electrode customized with an anti-miRNA probe for the selective recognition of miRNA-652. All the experimental parameters have been carefully evaluated, and the platform allowed to detect miRNA-652 in standard solution and human serum down to 0.4 nM, with a satisfactory repeatability of about 6 and 3 % respectively. The selectivity presence of other miRNA sequences was satisfactory demonstrated. In addition, we demonstrated the effectiveness of pre-concentration of miRNA by coupling the office paper-based electrode with an external disk made by chromatographic paper: the detection limit has been improved of 10-fold without the use of complex/expensive procedures. The presented manuscript represents an important step towards the development of a non-invasive, sensitive and TNBC-specific diagnostic platform that could improve patients' prognosis and quality of life, ulteriorly improved with pre-concentering properties of frugal supports as the external chromatographic paper-based ones. [Display omitted] [ABSTRACT FROM AUTHOR]

• A distributed constant type equivalent circuit model for paper-based lactate biofuel cells was proposed. • Parameter values using electrochemical impedance spectroscopy (EIS) were estimated. • Local EIS measurement was performed to demonstrate the validity of the equivalent circuit model. In this study, a distributed constant-type equivalent circuit model for paper-based lactate biofuel cells (PBFCs) where the anode and cathode are formed on the same plane was constructed, and a method of determining parameter values in the equivalent circuit model was proposed. When PBFC were prepared and the electrochemical impedance of the entire cell was measured, the Nyquist diagram produced a spectrum due to the current line distribution. Parameters, such as charge transfer and solution resistances, were calculated from the obtained spectrum using theoretical impedance equations derived from the proposed equivalent circuit model proposed. In addition, the behavior of the current distribution in the battery was evaluated in detail by moving the reference electrode on and performing local electrochemical impedance spectroscopy at multiple points on the electrode. The models and methods proposed in this study are good for evaluating systems affected by distributed current lines, such as flat batteries, and for determining cell design, electrode areas, and arrangements. [Display omitted] [ABSTRACT FROM AUTHOR]

Synthesis of affordable electrocatalysts with high efficiency at low cost is crucial for large-scale water splitting. Molybdenum carbide (Mo 2 C) has been suggested to be a promising alternative to noble metal based electrocatalysts for water splitting. In this paper, we fabricated a nanotextured coating of wrinkled Ni-doped Mo 2 C on carbon fiber paper (CFP) from Ni, Mo and carbon black (CB) via a molten salt method. Such a novel electrocatalyst, denoted as Ni-Mo 2 C CB /CFP, shows an overpotential of 121.4, 209.3 and 426.4 mV to achieve a current density of 10, 20 and 50 mA cm−2 respectively in acidic medium. The hydrogen evolution reaction (HER) performance of other as-prepared CFP based electrodes (bare CFP, Mo 2 C/CFP, Mo 2 C CB /CFP, Ni-Mo 2 C/CFP and NiC x /CFP) also tested. We found that the addition of carbon black and the doping of Ni could significantly improve the electrocatalytic performance of Mo 2 C/CFP in terms of overpotential, Tafel slope and exchange current density. This work demonstrates a facile and scalable route using molten salt method for the synthesis of high-performance electrocatalysts from non-precious compounds on carbon materials. Image 1 • Carbon fiber paper (CFP) was employed as a carbon source and substrate of Mo 2 C. • The addition of carbon black (CB) contributes to the refinement of Mo 2 C particles. • Ni-Mo 2 C/CFP composite was prepared from Ni, Mo, CFP and CB by a molten salt method. • The Ni-Mo 2 C/CFP electrocatalyst exhibits excellent catalytic performance for HER. [ABSTRACT FROM AUTHOR]

Cellulose is an attractive reagent for the elaboration of C-containing materials, but here, we also considered it as an O-provider for preparing macro, micro and nano-fibrous Nb 2 O 5 /C composites by a new mineralization with Nb 2 Cl 10 in anhydrous conditions. Our study highlights differences of reactivity between filter paper, microfibrillated or bacterial cellulose in connection with the crystallinity and the accessibility of the hydroxyl groups. The Nb 2 O 5 /C ratio was found to be adjustable (55–75% of Nb oxide) depending on the cellulosic precursor. Our composites were tested as electrodes that could be used as negative electrode in hybrid lithium-capacitor. Electrochemical characterizations of Nb 2 O 5 /C composites are reported and it was demonstrated that characteristics of the starting cellulosic reagents that influence physico-chemical properties of composites thus impact electrodes performances. Very interestingly, for 1C charging/discharging rates, capacities as good as thus of literature (150 mAh g−1) were obtained using our new sustainable synthesis protocol. [ABSTRACT FROM AUTHOR]

A novel and facile method by sewing low-cost fiber electrodes on paper is proposed to fabricate electrochemical paper-based analytical devices (ePADs). Prussian Blue (PB) and Ag/AgCl were deposited on carbon fibers to prepare the working and reference electrodes. The hydrophilic carbon fiber was employed as the counter electrode. All electrodes were sewed on the paper substrate. The linear voltammetry scanning (LSV) and physical characterization results showed that the physico-chemical characteristics of the prepared electrode were maintained after sewing. As a proof of concept, the ePAD fabricating by sewing was used to detect hydrogen peroxide (H 2 O 2). The limit of detection (LOD) achieved 0.9 µM and the ePAD possessed high anti-interference ability to a variety of common ions and biological molecules. Additionally, the robustness of the ePADs against bending (error 6.2 %) manifested that the ePAD had excellent practical applicability. The good reproducibility (3.65 %) displayed by the current responses confirmed that this strategy can be profitably adopted to easily assemble ePADs in a highly flexible manner. In addition, a user-friendly reagent-free ePAD was proposed to determine the content of H 2 O 2 in real water sample without treatment. The good recovery percentage (95.7–99.7 %) demonstrated the high feasibility of the reagent-free ePAD with facile carbon fiber-sewed electrodes in the detection of H 2 O 2 from complex water samples. These results confirm that the sewing method is feasible and promising. This work provides a new insight into fabrication of highly sensitive and highly selective ePADs with fiber electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

• First use of graphite and polycaprolactone composite electrode for electrochemical study of NBOHs;. • Proposal of a mechanism for the oxidation of 25H-NBOH and 25B-NBOH using cyclic voltammetry. • Quantification of 25H-NBOH and 25B-NBOH in synthetic urine and blotting paper without the need for complex sample preparation. The dramatic escalation in the quantity of new synthetic drugs in recent years has prompted the pursuit of novel methods for identifying and quantifying these substances. Notably among them are the substituted phenethylamines known as NBOHs and NBOMes. Electrochemical study and quantification of new psychoactive substances (NPS) 25H-NBOH and 25B-NBOH in synthetic urine and synthetic blotting papers are presented using differential pulse voltammetry (DPV) on a composite electrode (CE) made of graphite and polycaprolactone (PCL). Based on the cyclic voltammetry (CV) results, we propose that the drug oxidation mechanism comprises two main steps. Initially, it involves the oxidation of the secondary amine, necessitating the removal of one electron from the amino-nitrogen atom, leading to dealkylation. Subsequently, bromine or methoxy substitution takes place. Under the optimized experimental conditions for the differential pulse voltammetry (DPV) studies, analytical curves were obtained in the range of 100 to 800 ng mL−1 for 25H-NBOH and 100 to 700 ng mL−1 for 25B-NBOH (r² = 0.999), with detection limits of 19 ng mL−1 and 23 ng mL−1, respectively, and quantification limits of 64 ng mL−1 and 76 ng mL−1. The proposed method was employed for quantification of the drugs in synthetic urine and synthetic blotting papers, with recovery values between 95 % and 106 %, demonstrating no interference from the matrices. [Display omitted] [ABSTRACT FROM AUTHOR]

Most of the newer forms of carbon materials being demonstrated as potential anodes for lithium-ion batteries suffer a serious drawback in terms of their commercial perspectives due to their failure in the retention of a flat plateau in the charging/discharging profile. Here we present a facile and low-cost approach for the fabrication of solvent-free, binder-free anode material for the practical usage. A filter paper was coated with graphite using a pencil lead followed by pyrolysis (PyPF) and tested for its electrochemical performance. Galvanostatic charge/discharge experiments as carried out in half-cell configuration exhibited a specific capacity of 342 mAhg−1 with a constant plateau at 156 mAg−1 with 98% coulombic efficiency. This clearly shows the potential and competency of the material to be an inexpensive commercial anode. The role of graphite coating on filter paper was clearly manifested in the comparative studies with only pyrolyzed filter paper. Furthermore, full cell studies were performed using PyPF as anode and carbon coated LiFePO 4 as a cathode. A specific capacity of 120 mAhg−1 at C/5 rate with 141 WhKg−1 energy density with the retention of constant plateau and minimal polarization further emphasize the proficiency of PyPF as an anode for a commercial lithium-ion battery. Image 1 • An eco-friendly, binder-free and freestanding anode is developed for practical lithium ion battery. • Favorable plateau in the charge/discharge profile with minimal polarization is obtained. • A small quantity of graphitic carbon derived from pencil lead remarkably engender excellent charge/discharge profile. • Full cell study puts that this anode in scope of commercial lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract With the legalization of recreational cannabis use, there is a need to develop a rapid and accurate roadside test that can be used to analyze human saliva samples for Δ9-tetrahydrocannabinol (THC), the main psychoactive ingredient in cannabis. Here we demonstrate a novel drug detection method where THC is infused into carbon paper electrodes followed by electrochemical detection in a pH 10 aqueous solution. This method produces a linear, sensitive (down to ∼ 1 pmol), dose-dependent change in the oxidation peak current that varies with THC surface densities. These results, as well as the peak charge per real carbon surface area and linear current/scan-rate dependence, support a model for the distribution of THC on the carbon surface in a thin-layer configuration, facilitating the oxidation of the deposited drug. We also demonstrate electro-oxidation of the two major metabolites of THC, the psychoactive 11-hydroxy-tetrahydrocannabinol (OH-THC), and the non-psychoactive 11-nor-9-carboxy-tetrahydrocannabinol (COOH-THC), that also produce linear, dose-dependent changes in peak charge. However, COOH-THC exhibits a much lower Faradaic efficiency than OH-THC and THC, suggesting that variations in the THC functional groups affect the electro-oxidation of the cannabinoids. Overall, this work illustrates a novel, reproducible, and sensitive method for the analysis of THC and oxidation properties of its common metabolites that could be adapted for use with human saliva samples in future work. [ABSTRACT FROM AUTHOR]

Abstract Developing efficient bifunctional electrocatalysts and gaining fundamental understanding of reaction mechanisms are crucial for practical water splitting. Herein, a bifunctional NiSe 2 nanoparticles/carbon fiber paper (NSN/CFP) electrode is fabricated by the pyrolysis of Ni(NO 3) 2 on CFP, followed by a selenization step. The as-prepared electrocatalysts exhibit superior overall water splitting behavior in 1 M KOH with low overpotentials of 145 mV and 280 mV at current densities of 10 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) respectively, comparable to the performance of 20% Pt/C and RuO 2. Detailed compositional and morphological studies reveal that the NiSe 2 gradually transforms into an amorphous Ni(OH) 2 /NiOOH heterojunction during both HER and OER in alkaline medium. Based on these experimental results, an oxidation-induced self-reconstruction mechanism is proposed. Owing to the highly-oxidized Ni(OH) 2 /NiOOH active species, the self-reconstructed structure enhances the water splitting under fixed potentials for a prolonged time of 96 h with negligible current degradation. This work not only provides a facile route to fabricate efficient and stable electrocatalysts for large-scale water splitting but also reveals an underlying structural evolution mechanism, which guides the rational design of heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Abstract In this paper, carbon paper (CP) was modified by three-dimensional reduced graphene oxide (3DrGO/CP) and binders. Based on physical (field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy) and electrochemical tests (cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charging/discharging curves), the physical and chemical properties of 3GrGO/CP electrode were investigated. The physical characterization and electrochemical performance analysis indicated that the different binders significantly influenced the hydrophilicity and the wet surface area of electrode. Nitrogen doping three-dimensional reduced graphene oxide facilitates the electron transfer on electrode/electrolyte interface for both oxidation and reduction processes of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-HO-TEMPO), provides more reaction area and reduces concentration polarization. Therefore, the modified carbon paper electrode exhibits better electrochemical activity and reversibility compared with the pristine carbon paper electrode in a methyl viologen (MV)/4-HO-TEMPO redox flow battery (RFB). Graphical abstract Image 1 Highlights • N doping 3DrGO facilitates the electron transfer on electrode/electrolyte interface for 4-HO-TEMPO redox reactions. • The different binders significantly influenced the hydrophilicity and the wet surface area of electrode. • This simple modification method can effectively improve the performance of the RFB. [ABSTRACT FROM AUTHOR]

• Surface engineering of paper electrode through simple voltametric scanning and pre-anodization techniques. • Role of functional groups and influence on hydrogen evolution reaction. • Low-potential HER in 0.5 M H 2 SO 4 with two Tafel slope, 34.2 and 49.88 mV/ dec−1. Hydrogen evolution reaction (HER) is considered the most promising way to produce clean and sustainable hydrogen energy. Carbon-based materials have been discovered to be efficient for catalyzing HER reactions in addition to conventional noble metal-based electrodes. Surface engineering of electrodes through simple methods are important to enhance the electrochemical properties and to keep the cost economical. Herein, we tried to understand the influence of simple electrochemical pre-treatment methods on Paper electrode (PPE) surface towards electrocatalytical activity. The pretreatment methods involving simple voltametric scanning and pre-anodization has been carried out under various electrolytic conditions and investigated for their role on electrochemical activities. The pretreated electrodes were thoroughly characterized with surface morphological and electrochemical techniques. The pre-anodized disposable paper electrode (PA-PPE- H 2 SO 4) modified with pyrene butyric acid (PA-PPE- H 2 SO 4 -PBA) was found to show excellent electrochemical properties and exhibited a low-potential HER (Onset potential, E onset = -0.1 V Vs. RHE) in 0.5 M H 2 SO 4 with a Tafel slopes, 34.2 and 49.88 mV/ dec−1. The obtained results are substantially better than that of reported carbon-based electrodes, where the benefit of Platinum leaching out from the counter electrodes are speculated. The formation of edge-plane sites/defects, and functional groups on electrode surfaces and modification effect by PBA are the reason behind the increased the electrochemical response. Since paper has been used as a substrate for fabrication of the electrodes, possibility to use the same in future as a flexible current collector for self-powering wearable devices/sensors are anticipated. [Display omitted] [ABSTRACT FROM AUTHOR]

Analysis of neurotransmitters such as dopamine (DA) is essential to better understand brain-related mechanisms. In this context, paper-based electroanalytical devices are promising alternatives to the current techniques for affordable, user-friendly molecular quantitation. Conductive carbon-based and polymer-based inks such as carbon nanotubes (CNT) and polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) have shown several advantageous properties, such as resistance to the DA fouling occurring during the electrochemical detection. Here, the electrical and electrochemical properties of paper devices prepared from mixtures of the inks were investigated, as well as their DA detection performance (limit of detection and fouling resistance). The properties of these paper electrodes were found to be directly impacted by the choice of ink. CNT-based electrodes are more resistive than the PEDOT:PSS based ones, which are more capacitive. Also, electrodes with undercoats of CNT and overcoats of PEDOT:PSS, doped with organic solvents, better resist DA fouling and have lower limits of detection. The combination of carbon-based and polymer-baser inks allowed for optimizing DA detection, and highlights the versatility and adaptability of paper-based electrode fabrication. [ABSTRACT FROM AUTHOR]

• The 1D/2D MnO 2 /MXene heterostructures generate built-in electric fields that greatly accelerating the ionic and electronic diffusion/transport kinetics. • The synergistic mechanism generated by 1D/2D heterostructures achieve the balance between high energy storage activity and high active substance proportion of MnO 2 /MXene flexible electrode. • The quasi-solid-state FZIBs with MnO 2 /MXene paper-like film provide high total specific capacity and stability in flexible applications. Paper-like flexible electrode plays a critical importance role in booming the development of flexible energy storage devices. One-dimensional manganese dioxide (1D MnO 2) shows immense advantage in flexible zinc-ion batteries (FZIBs) on account of renowned tunnel crystal structure and high operating voltage. However, inherent inferior electrical conductivity and sluggish reaction kinetics seriously hinder the practical application of FZIBs, resulting in unsatisfactory rate capability and cycle performance. Herein, 1D/2D MnO 2 /MXene-5 heterostructure materials were constructed by electrostatic self-assembly, which were then prepared into paper-like membrane with high energy storage active substance ratio (95.2 %) towards high capacity and ultrastable FZIBs. The built-in electric field induced by the heterostructure accelerates the electron transfer, reduces the charge transfer resistance and promotes ion diffusion, enabling the 1D/2D phase collaboration to improve the zinc ion storage of the paper-like electrode. The design achieves a high total specific capacity (based on the total cathode mass) of 314.7 mAh g−1 at 0.1 A g−1 and ultrastable of 8000 cycles at 5 A g−1 with a retention of 81.1 %. Remarkably, quasi-solid-state FZIBs with MnO 2 /MXene-5 membrane can deliver an outstanding reversible capacity of 273.5 mAh g−1 at 0.1 A g−1 and maintain 500 cycles at 1 A g−1 across various bending angles without decay, demonstrating excellent stability. This work provides a novel approach for the targeted design of self-standing flexible electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

• The interconnected petal-like morphology of Co-MOFs on a flexible stainless steel substrate (FSS) was synthesized by using a cost-effective Reaction Diffusion Framework method. • The electrochemical properties of Co-MOFs/FSS were examined in different aqueous electrolytes. • The performance of supercapacitors using Co-MOFs/FSS was evaluated under varying concentrations of LiOH electrolyte. • A high-performance symmetric paper-soaked Co-MOFs/FSS//Co-MOFs/FSS device was designed and fabricated for supercapacitor applications. The electrolyte is a crucial component in supercapacitors (SCs), along with the electrode material, which can affect the electrochemical parameters, such as specific capacitances (C s), energy density (ED), cyclic stability, and potential window. Therefore, the present work explores the effect of different electrolytes on the performance of Co-MOFs/FSS electrodes for SCs. The Co-MOFs/FSS electrode was synthesized on a flexible stainless-steel (FSS) substrate using the reaction-diffusion framework method, and its structural, morphological, and compositional characteristics were analyzed. The SCs performance of Co-MOF/FSS was examined across multiple electrolytes (1M KOH, 1M LiOH, and 1M NaOH). The SCs performance of Co-MOFs/FSS increased in the following sequence: 1M LiOH > 1M NaOH > 1M KOH. Furthermore, the dependence of concentration variation of LiOH electrolyte on Co-MOFs/FSS for SCs was studied. In 2M LiOH electrolyte, the Co-MOFs/FSS demonstrated a maximum C s of 650 F g − 1 and specific capacity (C sp) of 262 C g − 1 at 5 mV s − 1. Furthermore, it exhibited a favourable retention rate of 71 % over 5000 GCD cycles at 10 mA cm−2. It also possessed higher ED and Power Density (PD) of 14.10 Wh kg−1 and 666 W kg−1 at 1 mA cm−2 respectively. Further, a flexible symmetric paper-soaked Co-MOFs/FSS//Co-MOFs/FSS device was fabricated, and its electrochemical performance was assessed. The fabricated device exhibited a higher C s of 122 F g − 1 and C sp of 171 C g − 1 at 10 mV s − 1. Additionally, it showed good retentivity of 46 % after the 3000th cycle at 15 mA; and exhibited higher ED of 6.78 Wh kg−1 and PD of 1500 W kg−1 at 6 mA. This study highlights the importance of selecting the appropriate electrolyte for enhancing the electrochemical performance of Co-MOFs/FSS electrode material. [Display omitted] [ABSTRACT FROM AUTHOR]

Al-air batteries are generally fabricated by rigid and heavyweight materials such as metal or plastic, meanwhile a bulky electrolyte solution either in static or circulation is requisite to ensure their steady operation. Therefore, they are less suitable for powering flexible and portable devices with lower power demand, such as wearable electronics, point-of-care test assays, RFID tags, etc. This work develops a flexible and lightweight Al-air battery with much less electrolyte storage, which is totally fabricated on a cellulose paper. The Al foil anode is embedded inside the paper substrate during paper-making process, while the air-breathing cathode is deposited onto the paper surface using an oxygen reduction ink. Despite its simple structure and low cost, this flexible Al-air battery can deliver a satisfactory power density of 19 mW cm−2 with alkaline electrolyte, and its operation lifespan is as long as 58 h with only 25 mg Al when saline electrolyte is employed. The corresponding Al specific capacity is as high as 2338 mA h g−1. In addition, this battery exhibits an excellent flexibility when facing different bending angles from 60 to 180° and multiple bending times greater than 1000. Furthermore, a flexible current or voltage output can be easily obtained by scaling up or stacking the present flexible Al-air battery, respectively, and the corresponding stacking efficiency is as high as 94%. In the future, non-metal oxygen catalyst will be employed to improve its environmental friendliness, and hot-pressing will be adopted to further increase its robustness to external deformation. • A flexible Al-air battery is developed for powering flexible and portable devices. • Al anode is embedded inside the paper, while ink cathode is deposited on the paper. • Peak power density of 19 mW cm−2 and specific capacity of 2338 mA h g−1 is obtained. • Battery performance is very stable even it is bended to 180° and by 1000 times. • Battery scaling-up and stacking is very convenient and highly-efficient (94%). [ABSTRACT FROM AUTHOR]

In this work, electrodes based on laser-scribed reduced graphene oxide were fabricated using filter paper as the substrate. To fabricate the electrodes, a water suspension of graphene oxide was filtered to produce a continuous and uniform film of graphene oxide on the filter paper surface. Subsequently, a CO 2 laser was used to "write" the working, counter and reference eelctroes by reducing graphene oxide in specific areas to define complete sensors. Referecnce electrodes were then coated with a commercial Ag/AgCl conductive paste to produce a quasi Ag/AgCl reference. As fabricated devices were employed as electrochemical sensors for detection of phosphate ions in water by employing the molybdenum blue method. This method exploits the reaction between molybdate and phosphate ions in acidic media leading to a Keggin-type complex (P M o 12 O 40 3 − ) which, being electrochemically active, enables the indiret detection of phosphate ions. Sensors exhibited high selectivity and sensitive detection of phosphate ions in a wide linear range, from 1 to 20 µM; with a limit of detection of 0.4 µM. To demonstrate that sensors could be utilized for in-situ phosphate ion detection, paper substrate was first pre-loaded with sulphuric acid and molybdate ions. During analysis, these chemicals were then desorbed directly into the test sample eliminating the need for any kind of external manipulation or reagent addition. Thus, this paper presents the fabrication of a portable, easy-to-use, biodegradable and fast phosphate ions sensor for in situ and real-time monitoring of water quality. [ABSTRACT FROM AUTHOR]

Water splitting associated with the conversion and storage of renewable energy is considered to be the most significant strategy to create hydrogen. Herein, an efficient self-supported electrode was developed by in-situ growth of interlayer expanded lamellar cobalt diselenide (CoSe 2 ) nanosheets (NS) on carbon paper (CP) substrate (CoSe 2 NS@CP). The analyses of TEM, SEM and XRD confirmed that the CP is homogeneously coated by few stacking layers of interlayer expanded lamellar structured CoSe 2 . This rationally designed nanostructure can provide more active sites for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The bifunctional electrode exhibits high electrocatalytic performance with −128 mV vs. RHE onset potential for the HER in 0.5 mol dm −3 H 2 SO 4 and +1521 mV vs. RHE for the OER in 1.0 mol dm −3 KOH. Besides, small electrolysis potentials of −201.1 mV vs. RHE and +1636 mV vs. RHE are needed to drive the HER and OER at current density of 100 mA cm −2 . Finally, a small overall cell voltage ( ca. +1.75 V) was used to drive the water splitting reaction in 1.0 mol dm −3 KOH. The CoSe 2 NS@CP electrode showed both excellent catalytic activity with overall current density of 100 mA cm −2 at 2.13 V and tremendous durability with negligible decrease in potential at a constant current of 20 mA cm −2 for more than 30 hours. Thus this rationally designed electrode material can be readily applied for large-scale water splitting process. [ABSTRACT FROM AUTHOR]

This study analyzed theoretically the effects of a carbon paper (CP)-based electrode on the performance of a vanadium redox flow battery (VRFB). Compared to conventional carbon felt-based electrode materials, the CP-based electrode showed superior characteristics in facilitating the redox reactions of VO 2+ / VO 2 + and V 2+ / V 3+ couples, such as better electrochemical activity and higher electronic conductivity. A three-dimensional, non-isothermal VRFB model developed in a previous study was applied to a range of single cell structures equipped with CP-based electrodes and flow channels in the current collectors. The model was then validated using the experimental data measured under the CP- and channel-based VRFB geometries. The model successfully captured the experimental trend that showed a higher discharging performance with increasing number of CP layers used for each electrode. The simulation results clearly showed that the activation overpotentials in the electrodes were reduced significantly using more CP layers, which dominated over the effects of increased mass transport limitation of vanadium ions due to the thicker electrode. [ABSTRACT FROM AUTHOR]

Abstract In this article, a flexible free-standing MoS 2 based paper-electrode for lithium-ion batteries (LIBs) was assembled according to a solution-based papermaking process and subsequent in situ carbonization. The ultrathin MoS 2 nanosheets as active materials were efficiently exfoliated from bulk counterparts using TEMPO-oxidized cellulose nanofibrils (CNF) as assistant agents. Meanwhile, the oxidized CNF was utilized both as biobased binder and fibrous skeletons for the fabrication of hierarchical MoS 2 hybrid films. The MoS 2 based nanoarchitectures were finally achieved with carbon nanotubes (CNTs) as conductive fillers and further in situ carbonized under argon atmospheres. The in situ carbonization improved the electrical conductivity and specific surface area dramatically. The flexible paper-electrode assembled with ultrathin MoS 2 nanosheets, carbonized CNF (C-CNF) and CNTs exhibited enhanced performance with a high specific capacity, nice rate capability, and long time cycling stability. The carbonized MoS 2 /CNF/CNTs hybrid film can directly act as an ideal paper-electrode for LIBs without using traditional metallic current collector makes it appropriate for the next-generation flexible/wearable electronics in future. Graphical abstract Carbonized MoS 2 nanosheets/cellulose nanofibrils hybrid films with enhanced conductivity can be directly used as ideal paper-electrode for LIBs without metallic current collectors. Image 1 [ABSTRACT FROM AUTHOR]

Porous 3-D current collectors have been shown to be the primary choice in replacing classical 2D aluminum foil in applicable developments, especially those using carbon-based current collectors. In this study, we investigated the impact of using a non-woven carbon (NWC) based current collector for sulfur electrodes, in terms of performance and practical use in a commercial battery, keeping in mind the simplicity of electrode preparation method. The benefits of using NWC as a 3D current collector include high sulfur utilization for even highly loaded electrodes, lower polarization, and the provision of an efficient electrolyte reservoir. High discharge capacities up to ∼1200 mAh g −1 can be obtained at moderate C-rates, with relatively good capacity retention (<1% loss per cycle) and practical loadings as high as 8 mAh cm −2 . [ABSTRACT FROM AUTHOR]

Abstract The structural design and synthesis of sulfur-carbon composite materials with high performance is still a major challenge for rechargeable lithium-sulfur batteries. Interconnected three-dimensional frameworks comprising multi-walled carbon nanotubes, graphene, or carbon particles offer a combination of constituent advantages and can thus be used to achieve superior energy conversion and storage properties. Herein, we designed and prepared free-standing three-dimensional sulfur papers containing interconnected highly conductive carbon materials, which enable to be flexible binder-free cathodes for Li-S batteries. The resultant sulfur-carbon composite paper cathode exhibited high reversible specific capacity of 1386 mAhg−1, good rate capability up to 5C, and excellent cycling performance (a capacity retention 68% after 400 cycles), all of which are significantly improved from those of bare sulfur cathode or sulfur-GO composite only. Rational design of cathode composition, structure, and a simple fabrication process can give insight into the development of various advanced cathode materials for high-performance Li-S batteries. Graphical abstract Image 1 Highlights • The composition of in-situ formed sulfur particles on the surface of GO with conductive carbons was designed and prepared. • Highly flexible and conductive S-GO/SP and S-GO/MWCNT papers were used the cathode for Li-S battery. • The use of composite papers allowed high reversible capacity and stable cycling performance. • The use of S-GO/MWCNT composite papers improved the rate capability. • The interconnected 3D framework was able to suppress the migration of polysulfides and irreversible agglomeration/deposition. [ABSTRACT FROM AUTHOR]

Abstract An in-situ electrochemical activation method was developed to activate the carbon fiber paper (CFP) for the highly efficient concentrated HNO 3 reduction. The defects and heteroatoms were introduced onto the surface of carbon fiber resulting in a significant improvement in the reactivity. Furthermore, the surface wettability of electrode was adjusted to enhance the accessibility of the active surface. Owing to these advantages, the activated-CFP electrode exhibits a higher current density (464.1 mA cm−2) for the electroreduction of 4 M HNO 3 compared to the conventional Pt electrodes (75.39 mA cm−2). Based on scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and contact angle analysis, the HNO 3 reduction mechanism on the activated CFP electrode was discussed. High activity as well as excellent electrochemical and chemical stability in the concentrated HNO 3 make the activated-CFP as an effective alternative for noble-metal electrode in the future industrial applications. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

• Enzymatic bioelectrode characterized for energy generation and biosensing purposes. • Bilirubin oxidase immobilized on carbon paper using PBSE as bifunctional crosslinker. • Biobattery successfully applied in powering a digital watch for over 2 h. • Biosensor revealed high sensitivity (606 μA mM−1 cm−2) and low LOD (1.3 μM) for O 2. • Response maintained (88%) for 34 days through constant bioelectrode reutilization. Biological systems can be envisaged as energy-sustainable solutions for both microenergy production to power small electronics and sensing purposes. In the present work, an enzymatic bioelectrode was characterized as biocathode in the fabrication of a biobattery and as biosensor for dioxygen detection. Carbon fibre paper was selected as transducer given its unique tailoring and electrocatalytic characteristics, being modified with carbon nanotubes for subsequent attachment of bilirubin oxidase enzyme. The immobilization process was based on a simple but effective method using the crosslinker 1-pyrenebutanoic acid N-hydroxysuccinimide ester, which creates stable bonds by maintaining a good response (88%) for over 34 days. The biobattery, that consisted of a zinc anode coupled with the developed biocathode, produced an open circuit potential of 1.69 V and maximum power of 40 μW, being capable of powering a digital watch for over 2 h. When applied as a dioxygen biosensor, the biocathode revealed high sensitivity of 606 ± 22 μA mM−1 cm−2 and low limit of detection of 1.3 ± 0.2 μM in chronoamperometric measurements at +0.4 V. The application of bilirubin oxidase in the fabrication of biobatteries is scarcely studied even given its advantages over other dioxygen reduction enzymes. Likewise, the use of the remarkable features of CP in dioxygen biosensing is yet to be explored. Therefore, this work stands as an interesting opportunity in the development of relatively simple and affordable bioelectrodes viably intended for energy and biosensing applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• 1T-MoS 2 was applied as a flexible and functional "spacer" to hybridize with Ti 3 C 2 T X MXene, forming flexible capacitive freestanding films. • The insertion of electrically neutral pseudocapacitive could mitigate the restacking of Ti 3 C 2 T X MXene layers and improves the capacity of the composite paper. • The supercapacitor fabricated with acidic gel electrolyte and composite electrode with randomly stacked MXene and 1T-MoS 2 in a mass ratio of 6:1 demonstrated optimal performance. In the case of increasing shortage of non-renewable resources, developing high-efficiency and high-capacity energy storage devices is critical. Supercapacitors have the potential of high-efficiency and high-capacity. MXene and 1T-MoS 2 are two kinds of high performance pseudocapacitive materials. However, the stacking and aggregation of MXene nanosheets greatly reduce its capacity. The poor conductivity of 1T-MoS 2 also limits the full expression of its excellent pseudocapacitive performance. A flexible MXene/1T-MoS 2 composite paper electrode is designed and prepared in this work where the restacking of MXene can be relieved and the whole electrode maintains the conductivity. The interior stacking structure of MXene and 1T-MoS 2 in the composite paper, as well as the gel electrolyte type are explored. The device constructed with the electrode composed of randomly stacked MXene and 1T-MoS 2 (mass ratio 6:1) and acidic electrolyte (PVA/H 2 SO 4 gel electrolyte) demonstrates the optimal performance. The specific areal and volumetric capacitances reach 561.2 mF cm−2 and 1268.17 F cm−3 at the current density of 0.8 mA cm−2 respectively, outperforming most of the previously reported values for MXene based supercapacitors tested in gel electrolyte. The supercapacitor has excellent deformation durability and long cycle stability, demonstrating promising prospect in future flexible electronics. [Display omitted] [ABSTRACT FROM AUTHOR]

• Self-supporting x Ni-WC@CFP catalysts with fold-like structure were prepared through one-step molten salt method. • 4M Ni-WC@CFP showed excellent HER activity in 0.5 M H 2 SO 4 (overpotential of 73 mV at 10 mA cm−2 and Tafel slope of 66.4 mV dec−1). • The increasing concentration of Ni(NO 3) 2 promoted first and then inhibited the catalytic performance of x Ni-WC@CFP electrocatalysts, resulting from the synergistic effect of Ni and W on hydrogen adsorption energy. Exploring high-performance and inexpensive electrocatalysts for hydrogen evolution reaction to substitute Pt-based compounds is important to sustain hydrogen production. Herein, WC based self-supported catalysts doped with different concentration of nickel nitrate solution (Ni(NO 3) 2) were synthesized on carbon fiber paper (CFP) by one-step molten salt method (abbreviated as x Ni-WC@CFP). With the increasing of Ni(NO 3) 2 concentration, fold-like structures were formed on the catalysts, which was conducive to active sites exposure. As Ni(NO 3) 2 concentration increased from 1M to 5M, the catalytic performance of the electrocatalyst showed a trend of increasing first and then decreasing. The optimal 4M Ni-WC@CFP showed comparable catalytic ability in 0.5M H 2 SO 4 with a low overpotential of 73 mV at 10 mA cm−2 and Tafel slope of 66.4 mV dec−1. However, excessive nickel doping would inhibit HER performance. The density functional theory calculation further verified the experimental results. The adsorption energy of hydrogen showed a decreasing trend with the rising amount of Ni doped in, while the W-H binding energy would change in an opposite direction as over doped Ni. This work provided an insight for the preparation of high-efficiency self-supported W-based electrocatalysts and expounded the influence trend of Ni doping concentration on the performance of electrocatalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Pd nanostructured catalysts were electrodeposited by surface-limited redox replacement reactions using the electrochemical atomic layer deposition technique. Carbon paper and Ni foam were used as substrates for the electrodeposition of the metal. Supported nanostructured Pd electrodes were characterized using electrochemical methods and scanning electron microscopy. Carbon paper and Ni foam produced good quality deposits with some agglomeration on Ni foam. The EDX profiles confirmed the presence of Pd particles. Cyclic voltammograms of the electrodeposited Pd on substrates showed features characteristic of polycrystalline Pd electrodes. In the acidic electrolyte a very weak oxygen reduction reaction (ORR) activity was observed on Pd/Carbon paper electrode when compared to Pd/Ni foam electrode. The Pd/Ni foam electrode showed improved ORR activity in alkaline medium. [Copyright &y& Elsevier]

Abstract Paper-based microfluidic fuel cells emerge as a promising clean energy sources for small-scale electronic devices, while their broad-based applications require a comprehensive understanding of their structure-performance relationships. Here in this work, we made attempt to identify the key structural parameters that impact the overall performance of paper-based microfluidic fuel cells. The influences of fuel crossover, cell resistance, limitations from both anode and cathode, and in particular microfluidic paper channel properties have been systemically investigated and optimized towards the best practices. Among various structural parameters, we unravel for the first time that the overall performance of these paper-based microfluidic fuel cells is largely dependent on the textural properties of microfluidic paper channels. By correlating the fuel cell performance with the unambiguously determined flow rate of electrolyte within different paper channels, we found that a greater flow rate which was achieved by using paper with larger mean pore diameter, could result in higher peak power density and open circuit voltage. This performance enhancement would benefit from minimized reactant depletion near electrode surfaces and suppressed fuel crossover. Technically, an open circuit voltage of 0.86 V and a maximum power density of 7.10 mW/cm2 can be achieved on a single cell (fuel: 4 M KCOOH; oxidant: air; electrolyte: 1 M KOH; catalyst: 0.2 mg/cm2 Pd/C on 0.15 cm2 graphite foil), and the maximum power output can be sustained for at least 1 h. The fuel cell power can also be easily increased proportionally when connecting two or more cells in series, which makes theses paper-based microfluidic fuel cells capable to power various electronic devices with different power requirements. [ABSTRACT FROM AUTHOR]

Abstract In this study, cathodic electrodeposition of manganese oxide onto reduced graphene oxide paper is carried out to prepare flexible and binder-free electrodes for electrochemical capacitors. Effects of electrodeposition potential and the amount of deposited mass on the electrochemical performance are examined. Hausmannite phase manganese oxide coated electrodes exhibit promising performance in charge-discharge and cyclic voltammetry measurements with specific capacitance of 546 F g−1 at current density of 0.5 A g−1 and 308 F g−1 at scan rate of 1 mV s−1, respectively. During potential cycling, phase transformation of Mn 3 O 4 to mixed-valent MnO x is observed. Consequently, MnO x nanostructures on self-standing reduced graphene oxide electrodes have 154% capacitance retention at 10000 cycles of cyclic voltammetry. Graphical abstract Image [ABSTRACT FROM AUTHOR]

An overview of the last trends in lab-on-chip technology highlights the continuous development of biosensing approaches in terms of simplicity, low-cost, and quick response, with a higher sensitivity and selectivity. In this context, electrochemical sensors arrived to overcome the need to develop small, accurate, portable and compact sensing devices, compatible with routine use in loco analysis, especially in point-of-care (POC) assessment. Herein, we have presented the first paper-based electrochemical sensor towards the detection of 3-nitrotyrosine (3-NT), a relevant oxidative stress biomarker. This innovative sensor was designed by, first, modifying paper to become a hydrophobic support and, second applying carbon and silver conductive inks to generate a three electrode-system on a small spot. An intensive voltammetric investigation of the paper-based screen-printed electrodes (SPEs), including the study of different redox-probes, scan-rate values, probe concentrations and supporting electrolyte solutions, confirmed their suitable and reliable electrochemical performance. Square wave voltammetry (SWV) was employed to assess the sensitivity of the proposed sensor at various concentrations of 3-NT, ranging from 500 nM to 1 mM, enabling a low detection limit (LOD) of 49.2 nM. The interference of co-existing species was also tested and good selectivity against 3-NT was accomplished. Overall, this flexible paper-based platform constitutes a promising sensor material towards a quick, sensitive, cost-effective, sustainable and reproducible detection of 3-NT biomarker. [ABSTRACT FROM AUTHOR]

This work describes the use of a capillary quasi-steady flow to improve the power and current output of a paper-based enzymatic glucose/O2 fuel cell. Anode and cathode of the fuel cell are made with screen-printed carbon electrodes properly functionalized with enzyme-based inks. The electrodes have been placed at both sides of a paper strip. The strip is connected to a paper-based microfluidic system that allows establishing capillary flow. Quasi-steady flows with different flow rates have been generated by modifying the paper materials that constitute the adsorbent pad of the system. The polarization curves of the fuel cell at physiological glucose concentration (5 mM, pH 7.4) show that convective mass transport generated by the capillary flow allows mitigating cathode current limitations and improves the overall fuel cell performance. Four different flow rates ranging from 0.22 ± 0.01 μL/s to 2.68 ± 0.30 μL/s were investigated obtaining an increase in the fuel cell power output up to 56%. [ABSTRACT FROM AUTHOR]

Due to highly conducting and extraordinary stable nature, carbon based materials expand the arms of energy storage devices in terms of supercapacitor. Hence, emphasis has been made to use flexible and free-standing multi-walled carbon nanotubes (MWCNTs) bucky paper synthesized by chemical vapor deposition for electrochemical supercapacitive electrode. The high specific capacitance of 270 F/g (2 mV/s) with superb stable behavior (88% at 10000 cycles) of bucky paper has promised as decent electrode in energy storage application. Aqueous symmetric supercapacitor (ASSC) device developed through bucky paper exhibits voltage frame of 1.6 V yielding specific capacitance of 91 F/g along with specific energy of 32 Wh/kg at a current density of 1 mA/cm 2 with trustworthy stability of 107% at 6000 cycles. The hands-on practicability to light up a red LED offers its promising approach in energy storage domain. [ABSTRACT FROM AUTHOR]

Herein we reported a novel routine to easily access graphene/polyaniline paper (GPp) as supercapacitor electrodes through controlled in-situ polymerization followed by roll coating. According to this routine, the load fraction of PANI can be easily controlled by feed ratio of aniline to GO. In the resulting GPp, PANI nanoarrays anchored graphene nanosheets and PANI nanofibers throughout the bulk coexist, and the former construct a three-dimensional network. As a result, the GPp as a freestanding electrode exhibits excellent electrochemical properties. It can deliver a high capacitance up to 838 F/g at a current density of 1 A/g, while keeps high retention of 93.7% at 10 A/g over 5000 cycles. Kinetics analysis shows that the GPp stores both surface capacitance and diffusion capacitance, but the former dominates the latter. [ABSTRACT FROM AUTHOR]

A novel polyprrole (PPy)-decorated hierarchical NiCo 2 O 4 nanoneedles was grown on highly conductive carbon fiber paper (CFP) for high performance asymmetric supercapacitor applications. The PPy-decorated hierarchical NiCo 2 O 4 nanoneedle on CFP (PPy-NiCo 2 O 4 @CPF) was grown by two steps. At first, NiCo 2 O 4 nanoneedle was grown by hydrothermal process and followed by the deposition of PPy through electrochemical method. The fabricated PPy-NiCo 2 O 4 @CPF electrode displayed the higher electrochemical performance. The specific capacitance was ∼910 F g-1 at a current density of 1 A g −1 and cyclic stability was ∼88% after 10,000 cycles. To explore real performance of the electrode, we have fabricated solid state asymmetric supercapacitor using PPy-NiCo 2 O 4 @CFP as positive and nitrogen doped reduced graphene oxide (N-rGO) as negative electrodes. The fabricated asymmetric device delivered a specific capacitance of 118.6 F g-1 at a current density of 1.0 A g −1 with a maximum energy density of 40.81 Wh Kg −1 (at a power density of 738.27 W Kg −1 ) and maximum power density of 3746.77 W Kg −1 (at an energy density of 13.53 Wh Kg −1 ). The impressive results suggest that flexible PPy-NiCo 2 O 4 @CFPs can be a promising electrode material for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Abstract The increasing demand for high-specific-energy batteries drives researchers to revisit Li metal anode. However, the formation and growth of Li-dendrite possibly leads to short-circuit of the battery, causing safety hazard of Li metal batteries. Therefore, it is quite necessary to regulate the plating/stripping behaviors of Li metal anodes to address this long-standing issue. Herein, we report the regulation of Li plating/striping behavior via manipulating the ratio of oxygen containing groups on reduced graphene oxide papers. It has been revealed that the electrochemical properties are highly dependent on the amount of carbonyl C O groups, which could associate Li+ and serve as a uniform nucleation site to guide Li plating. Furthermore, a high lithium ion diffusion coefficient of ∼2.09 × 10−14 m2 s−1 was enabled, around one magnitude higher than that of the Li lattice self-diffusivity (∼2 × 10−15 m2 s−1). As a result, stable dendrite-free Li metal anode is realized on the reduced graphene oxide paper with high C O group content (8.4%), which exhibits a low and stable overpotential of 50 mV for a long lifetime of 400 h. Our studies provide a fresh insight into the Li ion diffusion and its critical role in the regulation of the Li plating/stripping behaviors. [ABSTRACT FROM AUTHOR]

Abstract The preparation of coatings of manganese oxide and graphene nanoplatelets onto graphite paper by aqueous electrophoretic deposition is studied. This method is a fast and environmental friendly procedure for the manufacture of electrodes with enhanced specific capacitance for supercapacitors. The electrodes are prepared either sequentially, depositing consecutively the suspension of each material or simultaneously, from suspensions of mixtures of the two materials. Some of the electrodes show specific capacitances as high as 422 F g−1. The effects of (i) the electrophoretic deposition route chosen and (ii) the composition and load of the active electrode material deposited on the supercapacitor performance are studied. The symmetric supercapacitor cells show specific energy up to 9.2 W h kg−1 and specific power up to 1.8 kW kg−1 for 0.1 and 10 A g−1, respectively. The highest specific energy values are obtained in cells built with electrodes prepared by depositing first a layer of graphene nanoplatelets and then, manganese oxide. Highlights • Diverse effects founded depending on the electrophoretic deposition route chosen and the load of the active materials. • Deposition of the manganese oxide on the previously deposited graphene enhances the specific capacitance of the MnO 2. • High specific energy for industrial application. [ABSTRACT FROM AUTHOR]

The vanadium redox flow battery (VRFB) has emerged as a promising technology for large-scale storage of intermittent power generated from renewable energy sources due to its advantages such as scalability, high energy efficiency and low cost. In the current study, a three-dimensional(3D) Lattice Boltzmann model is developed to simulate the transport mechanisms of electrolyte flow, species and charge in the vanadium redox flow battery at the micro pore scale. An electrochemical model using the Butler-Volmer equation is used to provide species and charge coupling at the surface of active electrode. The detailed structure of the carbon paper electrode is obtained using X-ray Computed Tomography(CT). The new model developed in the paper is able to predict the local concentration of different species, over-potential and current density profiles under charge/discharge conditions. The simulated capillary pressure as a function of electrolyte volume fraction for electrolyte wetting process in carbon paper electrode is presented. Different wet surface area of carbon paper electrode correspond to different electrolyte volume fraction in pore space of electrode. The model is then used to investigate the effect of wetting area in carbon paper electrode on the performance of vanadium redox flow battery. It is found that the electrochemical performance of positive half cell is reduced with air bubbles trapped inside the electrode. [ABSTRACT FROM AUTHOR]

Nickel is one of the most common allergens found in cosmetics: a high exposure to nickel can cause serious effects on human health, as contact dermatitis or eczema. Considering the spread of this type of allergy among the population and the predominant use of cosmetic products, use portable and easy-to-use devices, which allow a quick and accurate assessment of nickel above the permitted limits, could represent a valid and alternative tool for the protection of human health. In this study, we developed a hybrid paper-polyester printed strip for fast, simple, and low-cost determination of nickel at concentrations consistent with the allowable limits in cosmetics, exploiting the differential pulse adsorptive stripping voltammetry in the presence of dimethylglyoxime as Ni-complexing agent. We report a novel configuration to produce an integrated fully-printed electrochemical device, in which the screen-printed electrode, printed on polyester, is successfully combined with a wax-printed filter paper disk in order to allow the investigation in treatment of complex matrices such as cosmetics ones. In addition, the use of filter paper allows to store all the reagents necessary for carrying out the determination. The method developed has allowed to work with small amount of sample (microliters level), obtaining a detection limit equal to 2 µM in standard solution and 5 µM in the two chosen matrices, namely cream and a synthetic gel. In order to evaluate the applicability, the device was also tested for the analysis of two commercial products, obtaining satisfactory results in terms of sensitivity and repeatability. The accuracy has been also evaluated by inductively coupled plasma-mass spectrometry (ICP-MS) measurements, with high correlation between the two approaches. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Gas diffusion layers (GDLs) were fabricated using non-woven carbon paper substrates with various thicknesses developed by Hollingsworth & Vose Co. Highly consistent carbon slurry containing Pureblack carbon and vapor grown carbon fiber (3:1 ratio) with 25wt.% Teflon was prepared by using a dispersion agent, Novec-7300 in isopropyl alcohol. Micro-porous layer was coated by using a fully automated Coatema coating tool with a uniform carbon loading of 2.6–3mgcm−2 using carbon slurry. The surface morphology, contact angle and pore size distribution of the GDLs were examined using SEM, Goniometer and Hg Porosimeter, respectively. Various cathode GDLs assembled into MEAs were evaluated in a single cell PEMFC under various operating relative humidity (RH) conditions using H2/O2 and H2/air as reactants. The peak power density of the single cell using the optimum carbon paper substrate thickness was about 1400 and 700mWcm−2 with H2/O2 and H2/air at 60% RH, respectively. It was found that the pore diameter as well as the corresponding pore volumes of the GDLs played a key role in exhibiting the optimum fuel cell performance. [Copyright &y& Elsevier]

The voltammetric behavior of the Ce(III)/(IV) half-cell reaction in various electrolytes containing 0.6 M Ce was investigated on both pristine and metal-modified carbon paper (CP) electrodes at three different temperatures (25, 40 and 55 °C) in order to find the most favorable electrochemical conditions. The pristine CP displayed robust electrochemical performance for up to 200 repetitive CV cycles while the Pt loaded electrode’s performance was stable for only 70 cycles, even though the latter exhibited a more reversible behavior, moving from a quasi-reversible to a reversible system ( D ox. = 4.0 × 10 −6 cm 2 s −1 and D red. = 2.5 × 10 −6 cm 2 s −1 ). The In and La metal modified electrodes did not show any improvement with regard to the kinetics or reversibility of the reaction. The addition of 1 M H 2 SO 4 to the base electrolyte enhanced the cerium reduction reaction by a factor of 3, ( −7.2 × 10 −3 A cm −2 ). The highest exchange current densities (j o ) were achieved at 40 °C for the CP-Pt (1 × 10 −3 A cm −2 ) attributable to the presence of the catalytic Pt. Elevated temperatures (40 and 55 °C) improved D and ΔE p. while also the mass transport parameters a) dynamic viscosity (∼1.5 mPa·s) and b) electrolytic conductivity (∼265 mS cm −1 ) of the Ce(III)/(IV) half-cell reaction. Overall, pristine CP and to a lesser extent CP-Pt demonstrated good stability with prolonged cycling and kinetics comparable with the ones of Pt and Pt based electrodes. [ABSTRACT FROM AUTHOR]

Flexible and robust amino-functionalized glass fiber filter paper/polyaniline (A-GFFP/PANI) composite films were fabricated as free-standing tensile-tolerant electrodes for high performance supercapacitors, by facile in-situ chemical oxidative polymerization of aniline on the surface of glass fiber filter paper (GFFP) in sulfuric acid solution, after surface modification. The results showed that the surface modification of GFFP with (3-aminopropyl)triethoxysilane played a role as bridge for connecting the polyaniline and glass fiber, resulting to unique polyaniline (PANI) coating and subsequently better electrochemical properties. The specific capacitance and electrical conductivity of the A-GFFP/PANI-1 electrode, which was fabricated via the conventional chemical oxidative polymerization of aniline with concentration of 0.18 mol/L, were 391.3 F/g and 2.78 S/cm, while the A-GFFP/PANI-2 electrode, prepared via rapid-mixing chemical oxidative polymerization under the same preparation condition, possessed the specific capacitance and electrical conductivity of 490.6 F/g and 1.83 S/cm. The capacitance retention of the A-GFFP/PANI-2 electrode (106. 8%) was also better than that of the A-GFFP/PANI-1 electrode (98.0%) after 2000 CV cycles at a scan rate of 100 mV/s, also owing to the bridging function of the functional silane. The A-GFFP/PANI-2 electrode retained 72.6% of its initial specific capacitance under the stress of 0.70 MPa for 1 h, indicating its good tolerance to tensile. [ABSTRACT FROM AUTHOR]

Here we developed a free-standing reduced graphene oxide (rGO)-polypyrrole (PPy) hybrid paper via electropolymerization on a paper-like graphene gel. This flexible hybrid paper displayed a uniform layered structure with PPy coated onto the graphene layers. A high areal mass of 2.7 mg cm −2 could be obtained. It delivered a greatly enhanced areal capacitance of 440 mF cm −2 at 0.5 A g −1 , in contrast to that 151∼198.5 mF cm −2 previously reported for graphene paper or polypyrrole-graphene paper. It can retain ∼81% of the initial capacitance at a high current density of 6 A g −1 . The combined high flexibility with outstanding electrochemical performance, makes such novel hybrid paper a promising electrode for flexible supercapacitors. [ABSTRACT FROM AUTHOR]

Paper-based working electrodes were modified by the addition of nanomaterials (carbon nanofibers, gold nanoparticles, graphene and hybrids of them), with the aim to increase the conductivity and to obtain an electroactive platform with improved analytical behaviour. The effect of the nanostructures was evaluated by using cyclic voltammetry and dopamine as electrochemical probe. The modifications with in-situ generated nanomaterials such as gold nanoparticles (AuNPs) or others requiring treatment like graphene oxide (GO), were optimized by factorial design. The characterization of the cellulose based electrodes by scanning electron microscopy (SEM) showed the distribution of carbon nanofibers and the presence of AuNPs around the cellulose fibers. The partial modification made by the carbon ink was also monitored by attenuated total reflection (ATR) spectrometry. Electrodes modified with rGO and AuNPs exhibited higher intensity peaks with more reversibility and reproducibility than unmodified paper. The highest intensities and lowest limits of detection were achieved with paper electrodes modified with hybrid nanostructures composed by both CNFs and AuNPs. [ABSTRACT FROM AUTHOR]

Cellulose paper-based energy storage devices have spurred significantly intrinsic advantages compared with the traditional batteries due to environmental benignity, recyclability and easy processing. In this work, the binary functional materials, which contains linear N-doped carbon nanotube (N-CNT, one-dimensional) and spherical C-coated MoS 2 (MoS 2 @C, zero-dimensional), are embedded into the porous recycled paper (RP, two-dimensional) derived from wastepaper via a facile and low-cost vacuum filtration method, and then the N-CNT/MoS 2 @C/RP film (N-M-RP film) featuring a unique compacted “point-line-plane” structure is obtained. In favor of the synergistic effect of high-conductive N-CNT, high-capacity MoS 2 @C and porous RP network, the prepared freestanding N-M-RP film presents a high strength of 35.2 MPa and a comparably low sheet resistance of 127.39 Ω sq −1 , and as an anode material for LIBs, the N-M-R film delivers a high reversible capacity, good cycling performance, superior rate capability and excellent electrochemical kinetics. Besides, the synergistic effect of “point-line-plane” structure on the improved electrochemical performances is also investigated. All the results indicate that the N-M-RP film comprised of 0D-1D-2D materials could be a potential candidate as a freestanding anode for LIBs. [ABSTRACT FROM AUTHOR]

A simple and inexpensive procedure of paper-based electrode (PE) fabrication using A4 size conventional paper, nail polish and carbon powder is reported. The device was prepared by spreading the carbon conductive ink directly onto the paper substrate using a paint-brush. The best composition of the conductive ink was 80:20% (m:m) carbon powder: nail polish and the best device was obtained with 100 mg (2.5 mg cm −2 ) of carbon conductive ink spread on the paper piece. The proposed device showed satisfactory stability in acidic, neutral and alkaline medium in presence of ferrocyanide ion used as electrochemical probe. Dopamine was selected as a target compound to evaluate the possibility of using the proposed device for electroanalytical purposes. Differential pulse voltammetry was used in these studies and dopamine detection was achieved at +0.13 V vs. Ag/AgCl sat in phosphate buffer solution pH = 7 with a detection limit of 5.2 μmol L −1 . The proposed device represents an interesting advance in the field of PE construction since it combines satisfactory electrochemical stability and electroanalytical performance with simplicity and widely available low-cost materials. Moreover, chemical modifiers can be easily added to the conductive ink. Therefore, this versatile device brings exciting possibilities for future electroanalytical applications mainly for those that require small and/or flexible devices, such as the amperometric detection in microfluidic systems. [ABSTRACT FROM AUTHOR]

Free-standing graphene composite papers exhibit very high flexibility and stability. Therefore, these materials are preferred as modular electrodes for some electrochemical applications, e.g. electrochemical sensors, supercapacitors, and batteries. Graphene composite papers are usually doped with different substances to improve their electrical conductivity, electrochemical performance, and stability. This work describes the fabrication of flexible and free-standing reduced graphene oxide (rGO) papers doped with phenazine, phenothiazine, phenoxazine, xanthene, acridine, and thiazole class of dye molecules. Fabrication procedure was applied by two basic steps: vacuum filtration of a dispersion containing GO sheets and dye molecule through a membrane and reduction of free-standing GO/dye paper to rGO/dye paper by treatment with hydriodic acid. Characterization of these rGO/dye papers were achieved by using scanning electron microscopy, scanning tunneling microscopy, energy dispersive X-ray analysis, powder X-ray diffraction spectroscopy, Raman spectroscopy, fourier transform infrared spectroscopy, UV–vis. absorption spectroscopy, four-point probe conductivity measurement and cyclic voltammetry techniques. Electrical conductivity and electrochemical performance studies indicated that acriflavine (Acr) doped rGO paper electrode exhibited the best performance for electrocatalytical oxidation of nitrite. When rGO/dye paper was applied as amperometric sensor for nitrite, the sensor was very stable, flexible, and reproducible. rGO/Acr paper demonstrated good quality parameters with sensitivity of 0.40 μAμM −1 cm −2 , detection limit of 0.12 μM, and linear range of 0.40–3600 μM. [ABSTRACT FROM AUTHOR]

MnO 2 was self-grown on carbon fiber paper (CFP) via a facile redox reaction, which is constructed by interconnected ultrathin nanosheets array. The CFP acts as both a supporting scaffold and a reducing agent for MnO 2 growth. The obtained MnO 2 /CFP composite was directly used as electrodes for supercapacitors, delivering a high specific capacitance of 713.7 F/g (0.5 A/g). Cyclic stability testing of the MnO 2 /CFP electrode reveals 86.8% retention in specific capacitance after 1200 cycles at 5.0 A/g. The nanosheet morphology of the MnO 2 on CFP brings about more efficient electroactive sites and facilitates the electrolyte penetration, allowing greater access for ions to active reaction sites. Hence, the attractive electrochemical performances exhibited by this MnO 2 /CFP electrode endow them potentially promising candidates for supercapacitors. [ABSTRACT FROM AUTHOR]

• Fibers and binder in the carbon paper have different oxidative stability. • Spatially-resolved VO2+ oxidation was tracked by Raman spectroelectrochemisrty. • Vanadium dimers formed preferentially at the oxygen-functionalized fiber surface. The elucidation of redox reaction mechanisms utilized in vanadium flow battery opens broad opportunities for targeted improvement of performance in specific power and energy efficiency. However, there is no unified agreement with regard to the catholyte reaction mechanism as common electrochemical methods such as cyclic voltammetry show general current-voltage response without distinguishing the various vanadium reaction intermediates involved in the redox reaction process. The literature describes several mechanisms that vary from electrode carbon composition, surface functionality, and electrolyte composition. Still, all proposed reaction pathways were derived from indirect models, and thus the introduction of an additional method for monitoring the speciation of vanadium moieties and for spatially resolving redox processes at the electrode/electrolyte interface is required for reliable validation of the reaction mechanism. Herein, we introduce a new spectroelectrochemical technique, which combines Raman spectroscopy with cyclic voltammetry as a powerful tool for deducing complex redox mechanisms at carbon paper electrodes. In particular, the vanadyl oxidation reaction mechanism was investigated on heated carbon paper with the help of in situ Raman Spectroelectrochemistry. Significant differences in the reactivity of carbon paper was found for electrodes activated at different temperatures and show that the fibers are more susceptible to oxidation, while the binder burns, which leads to a decrease in electrochemical active surface area. The monitoring of vanadyl oxidation showed two different reaction mechanisms on the fiber surface and the alternative one for the binder phase. Thus, this new spectroelectrochemical technique is an effective tool to track species transformation during redox reaction not only for catholyte in Vanadium Flow batteries but also for other systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Metal oxide nanoparticles as the electrochemically active second phase were incorporated into the paper-like flexible graphene-based hybrid electrodes. Its size and dispersion are crucial factors for determining the rate capability and cycling stability of the flexible hybrid paper electrode. Herein, we employ in-situ formed ultrafine monodisperse TiO 2 quantum dots (QDs, ∼4.0 nm) as the electrochemically active second phase, which are uniformly incorporated into the flexible hybrid paper via a simple mixed solvothermal reaction together with a vacuum filtration, aiming at achieving a high-rate and long-cycle flexible TiO 2 -based anode in lithium ion batteries (LIBs). By combining the advantages of both ultrafine TiO 2 -QDs and three-dimensional (3D) conductive networks, the as-fabricated TiO 2 -QDs-reduced graphene oxide (TiO 2 -QDs-RGO) hybrid paper electrode shows high reversible capacity of 201 mA h g −1 after 100 cycles at 0.1 A g −1 and superior rate capability as well as long cycle life of 1500 cycles with ∼80.6% capacity retention at 2.0 A g −1 . Detailed electrochemical analysis shows that the improved capability and cyclability of the hybrid paper electrode results from the integrated intercalation-based and interfacial lithium storage behaviors as well as the 3D fast electron/ion transfer of materials, which is ascribed to the ultra-small size of TiO 2 -QDs and the 3D self-standing conductive networks of the hybrid paper electrode. The results demonstrate the distinct advantages of our material design strategy, and also might pave the way for further studies of other flexible metal oxide/graphene hybrid paper electrodes for fast and long-life flexible anodes in LIBs. [ABSTRACT FROM AUTHOR]