Search

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.

The sandwiched membrane which consists of the sulfonated holey graphene oxide paper with the deposition of the sulfonated poly(ether ether ketone) (SPEEK/SHGO/SPEEK) membrane on its both sides has been prepared. This membrane is reported to have higher proton conductivity (155.6 ± 1.6 mS cm −1 ), but lower methanol permeability (7.05 ± 0.21 × 10 −6 cm 2 s −1 ) than Nafion ® 112 at 80 °C, whose respective values are 138.6 ± 1.4 mS cm −1 and 15.40 ± 0.46 × 10 −6 cm 2 s −1 , respectively. The specific structure of the SHGO comprising the sulfonated and holey graphitic plane plays an important role in the high performance of the SPEEK/SHGO/SPEEK membrane. First, the sulfonated structure could increase the overall density of the sulfonic acid groups in the membranes, which increases the number of proton exchange groups participating in the proton transport. Second, the holey structure of the SHGO provides an additional path for the proton transport, which well avoids the blockage of the proton transport by the high aspect ratio graphitic planes. Third, the sulfonated and holey structure could also increase the interlayer spacing of the graphitic planes in the SHGO paper, which would promote the proton transport as well. Finally, the presence of the SHGO paper with the layer-by-layer stacked graphitic plane would effectively retard the diffusion of methanol through the membrane. When evaluated in the semi-passive direct methanol fuel cell (DMFC), the cell with the SPEEK/SHGO/SPEEK membrane shows higher stability and exhibits a maximum power density 61.1% higher than with Nafion ® 112, which strongly suggests that the SPEEK/SHGO/SPEEK membrane could be used as the proton exchange membrane for DMFCs.

Herein, an environmentally-benign, facile, efficient, low-cost, scalable fabrication process of achieving flexible graphene paper electrode at ambient conditions is reported. By means of high-shear exfoliation of graphite in aqueous polyvinyl alcohol (PVA), the graphene/PVA dispersion is prepared. Various characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, etc.) confirm that the resulting dispersion is with the presence of high-quality, single to few-layered graphene sheets with thickness up to 1.68 nm, lateral size of 0.5–2 μm, and low defect density (ID/IG = 0.09). Further, the applicability of the in-situ exfoliated graphene/PVA dispersion is demonstrated for the fabrication of flexible conductive paper electrodes through a simple intermittent soaking-drying approach. The graphene paper electrode possesses an electrical sheet resistance of 15 Ω sq−1, without any additional annealing treatment and conductive additives. Finally, the graphene paper electrode is integrated with ionic-liquid incorporated PVA polymer electrolyte to develop the all-solid-state supercapacitor. It imparts a considerable specific capacitance of 222.96 F g−1 along with ~60% capacitance retention and ~100% coulombic efficiency after 6000 charge–discharge cycles. Meanwhile, the polymer electrolyte exhibits a remarkable ionic conductivity (4.63 × 10−4 S cm−1) together with a wide electrochemical stability window (5.1 V), favorable for device applications. The unique interwoven nanoporous conductive network of PVA-stabilized exfoliated graphene provides fast diffusion pathways to electrolyte ions, thus significantly enhancing the charge-storage performance.

The development of polypyrrole (PPY) flexible supercapacitors has been recognized as one of the most effective strategies for preparing advanced flexible energy storage devices. However, they are still limited by low mass loading and poor areal capacitance during charge-discharge process. Here, freestanding conductive film is designed and prepared by PPY/bacterial cellulose (BC) nanofibers in combination with graphene (RGO) through a simple in situ polymerization and filtering method. The porous and flexible BC nanofiber is used as a substrate and template for successive polymerization of PPY, which is responsible for such a large areal mass of 13.5 mg cm −2 . Thus, the high areal capacitance of 3.66 F cm −2 at 1 mA cm −2 and 2.59 F cm −2 at 50 mA cm −2 are achieved. The assembled symmetric supercapacitor by coupling of two freestanding electrodes delivers high areal capacitance of 1.67 F cm −2 , high areal energy density of 0.23 mWh cm −2 and a maximum power density of 23.5 mW cm −2 . Therefore, it is believed that this strategy holds great promise for design of freestanding conductive polymer electrodes on high performance flexible supercapacitors.

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.

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).

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.

In this article, a flexible free-standing MoS2 based paper-electrode for lithium-ion batteries (LIBs) was assembled according to a solution-based papermaking process and subsequent in situ carbonization. The ultrathin MoS2 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 MoS2 hybrid films. The MoS2 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 MoS2 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 MoS2/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.

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.

Developing efficient bifunctional electrocatalysts and gaining fundamental understanding of reaction mechanisms are crucial for practical water splitting. Herein, a bifunctional NiSe2 nanoparticles/carbon fiber paper (NSN/CFP) electrode is fabricated by the pyrolysis of Ni(NO3)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 RuO2. Detailed compositional and morphological studies reveal that the NiSe2 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.

In this study, a self-supported CFP@PANI@Fe3O4 cathode with three-layer structure was fabricated using a two-step synthetic route and characterized to reveal the morphology, composition and electrochemical performance of the novel electrode. The as-prepared CFP@PANI@Fe3O4 electrode showed enhanced electrocatalytic performance for p-nitrophenol degradation in electro-Fenton (EF) process with boron-doped diamond (BDD) electrode as anode. The results showed that for CFP@PANI@Fe3O4 cathode, 20 mg L−1 of p-nitrophenol was almost degraded in 60 min and the removal efficiency of total organic carbon (TOC) was 51.2% under the condition of applied current density 5 mA cm−2 and initial pH 3.0, which accompanied with more effective mineralization current efficiency (MCE) and less energy consumption (EC) compared with CFP and CFP@PANI electrodes. This enhancement was due to the increased electrocatalytic ability of in suit grown Fe3O4 on the surface of conductive substrates. Further investigation indicated that the fabricated electrode retained a high level of stability after consecutive runs. The reasonable reaction mechanism of p-nitrophenol was finally proposed according to the analysis of radical trapping experiments and fluorescence spectra, in which the hydroxyl radical (·OH) was deemed to the primary active oxidants. This work demonstrates the enormous potential of establishing an EF system with an efficient self-supported cathode based on in suit Fe3O4 immobilization for environmental remediation.

Ultra-thin, flexible supercapacitors for portable energy storage devices and intermittent electronic applications are closer to reality. This study developed a kind of thin flexible nanofibers paper electrodes (only about 12 μm in thickness) for all-solid-state supercapacitors, which combines the features of three-dimensional porous structure from bacterial cellulose (BC) and the advantages of highly ordered conductive polymer chains from polyethylenedioxythiophene (PEDOT). The capacity and conductivity of the conductive polymer PEDOT, which was coated evenly on the surface of BC nanofibers, were exploited sufficiently. And the flexible symmetric supercapacitors device assembled with the paper electrodes demonstrated an attractive electrochemical performance (a specific volumetric capacitance of 106.3 F cm-3 at a current density of 0.83 A cm−3) and an excellent cyclic stability. The electrical and mechanical properties of the devices still keep stable under various flexible conditions. So this material maybe a new choice for flexible energy-storage devices.

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.

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.

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.

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/AgClsat 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.

Molybdenum disulfide (MoS2) is considered as a promising candidate to Pt-based catalysts. Literatures report the active centers of MoS2 locate at its edges, while the perfect in-plane domains are not active. In this study, a simple Co Mo S precursor decomposition approach is used to synthesize Co-doped MoS2 in-situ grown graphite paper (GP) substrate. Electrochemical analyses reveal the Co-doped MoS2 possesses excellent electrocatalytic activity comparable to Pt. Density functional theory (DFT) calculations indicate the inert in-plane S atoms neighboring the doped Co atoms become active towards triiodide reduction, as revealed by the adsorption energies (Ead) of iodine atom decreasing from 0.36 eV to −0.52 eV, identical with value obtained from Pt (−0.52 eV). Due to increased active sites, highly conductive of GP, and excellent electrical connection between Co-doped MoS2 and GP substrate, the dye-sensitized solar cell fabricated using Co-doped MoS2/GP as counter electrode (CE) shows higher photoelectric conversion efficiency (7.26%) than those based on MoS2/GP CE (6.57%) and platinized F-doped tin oxide (Pt/FTO) electrode (6.87%).

The rapid growth of environment pressures and fast depletion of fossil fuels compel public to pay more attention on developing affordable and efficient catalysts for renewable energy production. Metal (Co, Fe, Ni, etc.) phosphide nanoparticles uniformly encapsulated in porous N,P-codoped nanofibrous carbon coated on carbon paper (MeP@NPC/CP) are prepared through one-pot carbonization-phosphorization strategy, which are potential for effective electrocatalytic water reduction/oxidation reactions. The well-designed self-supported structure and the abundant accessible active centers together contribute to the high electrocatalytic performance for hydrogen and oxygen evolution. Remarkably, an alkaline electrolyzer assembled from CoP@NPC/CP as cathode and anode can afford the current density of 10 mA cm−2 at the voltage of 1.67 V for overall water splitting in alkaline media with excellent stability. The easily prepared route with suitable structural and textural properties endows this self-supported materials with versatile function as abundant metal catalysts for realistic energy conversion and storage systems.

Transition metal phosphates with hollow structure have attracted substantial attentions as high-performance electrocatalyst for oxygen evolution reaction (OER). However, these electrocatalytic materials need conductive carrier to realize efficient charge transfer and further improve the OER activity. In this work, ZIF-67 derived hollow NiCo phosphate nanocages supported by waste paper-based carbon aerogel (NCP@WPCA) was prepared as high-efficiency and stable electrocatalyst. Benefited from the enhanced electrochemical active surface area and fast gas emission, the NCP@WPCA catalyst exhibits superior OER activity with low overpotential of 351 mV at current density of 10 mA cm−2, along with good stability in alkaline solution. Additionally, the waste paper-based carbon aerogel as the carrier for electrocatalysts achieves low-cost waste reuse.

Graphitic layer of carbon has been deposited on the surface of cellulose paper by simple pencil drawing approach. The edges of exfoliated multilayer graphene sheets formed during pencil drawing on the rough paper surface causes the enhancement of electrochemical capacitance. One step chemical polymerization technique has been adopted to fabricate polyaniline nanofibers on hydrophobic pencil drawn graphitic layer on the cellulose paper. These polyaniline coated pencil drawn paper electrodes were used to fabricate all-solid-state symmetric supercpapcitors with superior performance in comparison to similar pencil drawn paper electrodes without polyaniline. All-solid-state symmetric supercapacitor with paper based multilayer graphene-polyaniline nanofiber electrodes exhibits specific capacitance of 28.37 F g−1, areal capacitance of 93.64 mF cm−2, energy density of 8.32 µW h cm−2, and power density of 39.97 µW cm−2. It also shows excellent cyclic stability with initial increment to a maximum value and then decrease to 91.5 % of the maximum value after 5000 cycles. It is interesting to note that it retains 134.28 % of initial areal capacitance after 5000 cycles.

Herein, a series of three-dimensional Ni2Fe-SDS-LDH/CFP non-precious metal electrocatalysts in a simple hydrothermal route using sodium dodecyl sulfonate (SDS) as an interlayer spacer agent, and carbon fiber paper (CFP) as a conductive substrate was tailored. The electrocatalytic performance towards oxygen evolution reaction (OER) in alkaline medium was investigated. The results demonstrate that the OER activity improvement is mainly related to the increased interlayer distance from 0.76 nm to 2.49 nm depending on the intercalated amount of SDS in Ni2Fe-LDH, and resulting in the enhanced superior surface characteristics (e.g., larger specific surface area, bigger pore size and pore volume). Among all the samples, the Ni2Fe-SDS-LDH/CFP (molar ratio SDS/Fe = 1.5) showed the best OER performance (η@10 mA cm−2 = 289 mV, Tafel slope = 39 mV dec−1) comparable with the commercial IrO2 catalyst, which corresponded to the largest interlayer space of 2.49 nm.

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.

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.

In this paper, we synthesize a new type of Ni-Co selenides (Ni 0.34 Co 0.66 Se 2 nanorod) on carbon fiber paper (CFP) as flexible electrode for supercapacitor. Comparing with NiCo 2 O 4 and NiCo 2 S 4 , the Ni 0.34 Co 0.66 Se 2 exhibits superior capacitive performance including high areal capacitance (2.61 F cm −2 at 4 mA cm −2 ), good rate capability (75% of retention from 4 to 20 mA cm −2 ) and excellent long-term cycling stability (only 7.4% of loss after 6000 cycles). When assembled into a symmetric supercapacitor, the as-obtained, Ni 0.34 Co 0.66 Se 2 based device possesses a volumetric capacitance of 14.55 F cm −3 at 1 mA cm −2 , and a volumetric energy density of 0.47 mWh cm −3 at 10 mA cm −2 , which are superior to most of the symmetric supercapacitors reported previously. Then we explore the energy storage mechanism of Ni 0.34 Co 0.66 Se 2 by monitoring the changes in component, morphology, electroactive surface area (ESA) and electron transport characteristics. It is found that the Ni 0.34 Co 0.66 Se 2 species suffer from serious Se loss and transform into Ni x Co 1-x O gradully during charge/discharge cycles, but the ESA increases significantly in this process. In addition, the Ni 0.34 Co 0.66 Se 2 electrode possesses lower internal resistance, indicating its good electron transfer properties. Both these factors will compensate the performance degradation from Se loss, resulted in better rate capability and cycling stability for Ni 0.34 Co 0.66 Se 2 electrode. Therefore, it is believed that the proposed 3D Ni 0.34 Co 0.66 Se 2 nanorod array modified CFP with optimizational component and structual design opens a new horizen in the development of high-performance flexible supercapacitor electrode with new charge storage mechanism.

Natural cellulose fibres are proposed as promising components for bioderived photoanodes and polymer electrolytes in dye-sensitized solar cells (DSSCs). In particular, TiO2-laden paper foils, prepared by simple papermaking, can be applied to several substrates (conductive glass or plastics) instead of the high-temperature sintered traditional commercial pastes. In addition, nanoscale microfibrillated cellulose is used as reinforcing filler in acrylate/methacrylate-based thermo-set polymer electrolyte membranes prepared by means of fast, low-cost and green UV-induced free-radical photopolymerization. The laboratory-scale quasi-solid state paper-DSSCs assembled with cellulose-based electrodes and electrolytes guarantee sunlight conversion efficiencies as high as 3.55 and 5.20% at simulated light intensities of 1 and 0.2 sun, respectively, along with an excellent efficiency retention of 96% after 1000 h of accelerated aging test. The simple, low cost and green approach here specifically developed opens up intriguing prospects in the design of bio-inspired energy conversion devices showing high performance, outstanding durability and truly sustainable characteristics.

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.

A novel polyprrole (PPy)-decorated hierarchical NiCo2O4 nanoneedles was grown on highly conductive carbon fiber paper (CFP) for high performance asymmetric supercapacitor applications. The PPy-decorated hierarchical NiCo2O4 nanoneedle on CFP (PPy-NiCo2O4@CPF) was grown by two steps. At first, NiCo2O4 nanoneedle was grown by hydrothermal process and followed by the deposition of PPy through electrochemical method. The fabricated PPy-NiCo2O4@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-NiCo2O4@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-NiCo2O4@CFPs can be a promising electrode material for supercapacitor applications.

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 (CoSe2) nanosheets (NS) on carbon paper (CP) substrate (CoSe2 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 CoSe2. 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 H2SO4 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 CoSe2 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.

A low-cost and efficient MoS 2 /graphite paper (GP) counter electrode for dye-sensitized solar cells (DSSCs) is first fabricated by a simple and effective solution processed route. Photo-electric conversion efficiency of 6.48% is obtained for the DSSC adopting MoS 2 /GP, better than the device (6.22%) employing platinized F-doped tin oxide (Pt/FTO) electrode. Because highly conductive GP is performed as a substrate, and the mechanical adhesion and electrical connection between the MoS 2 film and the GP substrate are strong, the series resistance of MoS 2 /GP is much smaller than that of Pt/FTO. A comparable charge transfer resistance of MoS 2 /GP to Pt/FTO is found to be another factor for the better performance. Due to the MoS 2 prepared here possessing relatively high crystallinity and firmly being anchored on the GP substrate, MoS 2 /GP as well exhibits high stability. Hence, excellent electrochemical activity, high stability, facile preparation and low material cost of the MoS 2 /GP electrode offer it a promising potential for large-scale production.

Self-pumping fuel cells supported on filter papers are constructed by using hydrazine monohydrate as a fuel and potassium permanganate as the oxidant. Cost effective catalysts, namely, Cu nanoparticles (NPs), functionalized multiwalled carbon nanotubes (f-MWCNTs) and Cu-NPs@f-MWCNTs composite are synthesized and loaded onto carbon cloths, which are employed as the electrodes. The cells are operated at room temperature. The Cu-NPs@f-MWCNTs composite contained 75% and 25% of Cu-NPs and f-MWCNTs, respectively. The morphology of the composite comprises of Cu-NPs flanked to the tubular structures of f-MWCNTs, which resulted in improved electrocatalytic activity, compared to pristine Cu-NPs (which tend to aggregate severely) and pristine f-MWCNTs. The electrocatalytic activities of Cu-NPs@f-MWCNTs and Cu-NPs are comparable and superior to f-MWCNTs for hydrazine oxidation. Multiple cells with different catalyst combinations at the anode and cathode are electrochemically characterized. The cell with Cu-NPs@f-MWCNTs composite at the anode and with f-MWCNTs at the cathode produced the highest power density of 3.57 mW/cm2 at 0.89 V. For this catalyst combination, the cell retained an open circuit voltage between 1.85 V - 1.74 V for more than ten minutes of operation. Although the cell current density declined over time, it could be recovered to its original value by replenishing the cell with fresh anolyte and catholyte streams.

Dealloyed ternary Cu@Pt-Ru core-shell electrocatalysts supported on carbon paper (CP) are fabricated by cyclic-co-electrodeposition and selective copper dealloying (CCED-SCuD). The physical properties of this catalyst such as surface and bulk compositions, electronic structure modification, phase structure, crystallite size, compressive lattice strain, and morphology were characterized by X-ray photoemission (XPS), inductive-coupling plasma atomic spectroscopy (ICP-AES), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscope, and transmission electron microscope (TEM). The best catalyst is Cu@Pt-Ru/CP, having core-shell structure with a Cu rich core and a Pt-Ru rich shell with grain size around 100 nm. Cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) reveal that ternary Cu@Pt-Ru/CP gives significantly low onset potential and high activity towards methanol electrooxidation reaction (MOR), achieving specific peak current at 265 mA.mg Pt −1 , which is significantly higher than that of dealloyed binary Cu@Pt/CP (211 mA.mg Pt −1 ) and pure Pt/CP (170 mA.mg Pt −1 ). The highest current stability is found for the ternary Cu@Pt-Ru/CP with decay rate at 2.3 × 10 −3 mA.mg Pt −1 .s −1 . The enhancements of both activity and stability of the Cu@Pt-Ru/CP from the higher electrochemical surface area (ECSA) are major reason, which originates from the higher exposed surface of Pt, while the higher compressive lattice strain, electronic structure modification, and bi-functional mechanism are minor reason. However, the lower current density (J P ) of the ternary Cu@Pt-Ru/CP suggests lower intrinsic reactivity.

In this study, paper supported flexible electrodes for supercapacitors are prepared by paper-making process with the hardwood fiber (HWF), multi-walled carbon nanotube (MWCNT) and NiCo2S4 powder. Compared with previous reported cellulose nanofiber (CNF), nickel foam and carbon cloth supported electrodes, the HWF supported paper electrodes demonstrate its advantages of low-cost, mass production, low-thickness and superior flexibility. It can achieve a high specific capacitance of 1725 F g−1 at 1 A g−1, a remarkable rate retention of 79.3 % from 1 A g−1 to 10 A g−1, an ultrahigh volumetric specific capacitance of 246.4 F cm−3 at 1 mA cm−2 and an excellent cycling stability at 20 A g−1 after 5000 cycles. The as-fabricated HWF supported flexible asymmetric supercapacitors (ASCs) have achieved excellent volumetric specific capacitance of 10.25 F cm−3 and energy density of 10.1 mWh cm−3 with power density of 93.9 mW cm−3. All results suggest that the paper-making method and the HWF supported paper electrodes provide great opportunity for developing high-performance flexible energy-storage electrodes with the feasibility of mass production.

Visualization of latent fingermarks has ever been realized through electrochromism (EC) on stainless steel used as an electrode of electrochromic device (ECD). However, enhancement of fingermarks on paper using EC remains unresolved. Considering the hydrophobicity differences between the protruding and the concave parts of sebum-containing fingermarks, we attempt to devise ECDs capable of visualizing latent fingermarks on copperplate paper. It is demonstrated that the sulfonated viologen, 1,1′-bis(3-sulfonatopropyl) viologen can be used as an excellent chromophore for latent fingermarks enhancement on copperplate paper using EC, with either 1,1′-ferrocenedimethanol, or vitamin C or potassium ferrocyanide/potassium ferricyanide as the electron mediator. The as-fabricated ECDs can display the characteristic second level details of latent fingermarks left on copperplate paper under a voltage of -1.2 V. This work opens a new avenue for visualizing latent fingermarks on copperplate paper, which is a frequently-used potential physical evidence in office and daily life that may be useful for forensics.

To enhance Pd electro-catalysts in their electro-catalytic activity for C-C bond breaking and tolerance stability, Pd was electrodeposited on high-porosity 3D reduced graphene oxide (rGO) aerogel paper. For comparison, the Pd was also coated on other three different carbon material surfaces: bare carbon fiber paper (CFP), and CFP modified with either 2D graphene oxide (GO) and 2D rGO nanosheets. The Pd/3D rGO aerogel paper exhibits higher catalytic activity toward the electro-oxidation of ethylene glycol in alkaline media and higher excellent tolerance stability than other electrodes due to ultra-high porosity of the 3D rGO support leading to high active electrochemical surface area of the as-fabricated Pd catalyst electrode. In addition, the hydrodynamic diffusion of ethylene glycol to the cayalyst surface investigated in this work plays a major role to the catalytic activity of the as-prepared electrocatalyst. The Pd/3D rGO aerogel rotating disk electrode exhibits a high anodic current density of 267.8 mA cm −2 at 3000 rpm. This high-performance Pd/3D rGO aerogel may be practically used as the high-efficiency anode of direct ethylene glycol and other related alcohol fuel cells.

In this work, a sensitive and reliable electrochemical platform was developed for catechol (CC) and hydroquinone (HQ) individual and sensitive simultaneous detection. Due to the outstanding advantages of low cost, excellent flexibility, large surface area, and good conductivity, an exfoliated graphite paper (EGP) was used as a supported electrode for gold nanoparticles (AuNPs) electrodeposition to fabricate a sensor (AuNPs/EGP). Scanning electron microscope and cyclic voltammetry results revealed that AuNPs/EGP was successfully prepared with multi-layered structure and enhanced electron transfer ability. Under the optimized conditions, the sensor showed wide linear range for CC and HQ detection of 5.0 × 10 −7 - 1.0 × 10 −4 mol/L and 7.0 × 10 −8 - 1.0 × 10 −4 mol/L with limitation of detection (S/N = 3) of 4.13 × 10 −8 mol/L and 2.73 × 10 −8 mol/L, respectively. And the proposed sensing platform was successfully applied to the simultaneous determination of CC and HQ in real samples of three kinds of water with reliable recovery. The low cost, facile preparation, and attractive electrochemical performances made the graphite paper based sensor promise perspectives in the field of electroanalysis.

We present a novel approach for the synthesis of silver nanoparticles capped with oleylamine (AgNPs/OLA) and its application in conductive ink for electroanalytical application. The synthesized OLA capped AgNPs was characterized with TEM, UV-Vis, EDX, FTIR and TGA to confirm the size, composition and surface modification of NPs. In this paper, we report conductive ink printing using a pen to achieve a best conductivity value of 0.11 × 105 Scm−1. A 10 wt% AgNPs nano-ink solution was used for printing conductive electrodes (counter, reference and working) on-to photo paper and sintered at 150 °C for 1 h to achieve metallization. We demonstrated successful application of printed conductive electrodes in cyclic voltammetry (CV) measurement. To ensure the continuity of conductive pattern, we demonstrated the lighting of LED when conductive track was connected to a 9 V battery. This report shows that paper-based flexible electrodes are user-friendly, cost effective and useful for multiple analyses in CV compared to other printed electrodes.

Ethanol co-laminar flow fuel cells operating at room temperature have rarely been reported, primarily due to problems associated with the kinetics of ethanol oxidation. In this work, we present a study of the effect of ethanol concentration, pH of anodic and cathodic streams, and nature of the oxidant on the performances of an acrylic cell and a paper-based, membraneless co-laminar flow fuel cell (LFFC), with total cell volumes of 14.29 cm3 and 0.62 cm3, respectively. Additionally, this work reports the synthesis of a Pd-NiO anodic nanocatalyst by a simple, fast, and environmentally friendly method in order to match the clean, easy-to-use, and simple fabrication methods of these ethanol co-laminar flow fuel cells. The synthesized Pd-NiO exhibited a crystallite size of 8.1 nm and an average particle size of 8.7 nm for Pd-NiO/C. The highest performances were obtained by combining an alkaline anodic stream with an acidic cathodic stream, increasing the cell voltage, and decreasing cathodic limitations caused by the simultaneous occurrence of oxygen reduction as well as hydrogen reduction reactions. With these improvements, power densities of 108 and 85.5 mW cm−2 were obtained for the acrylic and the paper-based co-laminar flow fuel cell, respectively, which are the highest values reported to date for ethanol LFFCs at room temperature.

A free-standing oxygen-deficient hydrogenated TiO2 nanorod arrays decorated carbon paper (CP) electrode (TiO2-x NRAs/CP) is fabricated by a facile thermal reduction approach and developed as a robust anode for microbial fuel cells (MFCs). The oriented 3D nanostructure provides a fast electron transportation pathway for the electron transfer and large accessible areas for bacterial colonization. Also, the introduction of oxygen defects into TiO2 can further enhance its bio- and electrochemical activity as well as biocompatibility. Consequently, the MFCs with TiO2-x NRAs/CP as anode delivers a maximum power density of 2576.3±33 mW m−2, which is much larger than the MFCs with pristine TiO2 NRAs/CP and CP anode. This work demonstrates the first use of oxygen-deficient TiO2 NRAs/CP as an advanced anode for MFCs and provides a new path for performance improvement for metallic oxide anode MFCs.

Highly efficient and durable anode electrocatalysts are the key to boost the performance of direct organic-molecule fuel cells (DOMFCs), yet there are still many challenges need to be solved. The PdPt alloy nanocrystals have been regarded as the most promising anode catalysts of DOMFCs, and the further improvement of their catalytic performance has attracted much attention. The effective routes includes tailoring the surface structure and optimizing the alloy composition of PdPt nanocatalysts. The high-index faceted structures possess high density of terraces and atomic steps which are efficient for electrooxidation reactions of small organic-molecule fuels, such as formic acid and ethanol. In particular, electrochemically-controlled synthesis methods present unique advantages in achieving such high-index faceted nanostructures. The current paper reports a direct electrodeposition of PdPt concave nanocubes on carbon paper (denoted as PdPt-CNC/CP). The prepared PdPt-CNC/CP has high-index faceted surface structures varying from {610} to {830}. When served as electrocatalysts, the PdPt-CNC/CP brings in outstanding mass specific activity and durability towards both formic acid oxidation reaction (FAOR) and ethanol oxidation reaction (EOR). More importantly, the selectivity of complete oxidation pathway through the cleavage of C-C bond on PdPt-CNC/CP during EOR in alkaline solution has been confirmed through NMR analysis. Based on the convenient method of direct electrodeposition of PdPt concave nanocubes on carbon paper and their excellent catalytic activity and durability, the PdPt-CNC/CP catalysts have potential advantages in being used as catalyst layers directly for membrane electrode assembly (MEA) in fuel cells, due to the reduced catalyst loading and simplified assembly process in comparison with traditional preparation procedure.

The composite of manganese dioxide (MnO2) with high theoretical capacity (1230 mAh g−1) and carbon nanofiber paper with high electrical conductivity is attracting attention as a next-generation battery anode material. This study proposes a facile route for coating mesoporous MnO2 on the carbon fiber by low-temperature reduction of KMnO4 and intercalating graphene into the carbon paper through vacuum filtration. The MnO2 coated carbon nanofiber (MOCNF) is synthesized in the form of paper, while maintaining the flexibility and strength with graphene intercalated between MOCNF papers. The resulting paper is applied for the lithium ion battery anode without any current collector, binder and conductor. This free-standing electrode has a discharge capacity of 945 mAh g−1 at 100 mA g−1 and shows a high discharge capacity of 545 mAh g−1 at 1000 mA g−1 even after 1000 cycles. This stable cycle performance originates from the mesoporosity of MnO2 and the intercalation of graphene, which accelerates the kinetics of redox reaction and mitigates the electrochemical isolation of MnO2 from the carbon nanofibers. This paper-type material can be a next-generation battery anode with considerable flexibility and capacity. Furthermore, the facile method of MnO2 coating and graphene intercalation can be applied to the other electrode synthesis.

Amorphous MoS2 Nanoflakes are grown on the outer and inner surfaces of N-doped carbon microtubes prepared by the carbonization of the biomass of willow catkins to fabricate N doped carbon microtubes@amorphous MoS2 (NCMTs@A-MoS2) and subsequently the as-prepared NCMTs@A-MoS2 and 2D reduced graphite oxide cross link to form 3D NCMTs@A-MoS2/RGO composite paper by a simple vacuum filtration. This novel three dimensional nano/micro hierarchical structure has the superior advantages of nano and micro materials, such as decreasing the diffusion lengths of lithium ions and preventing the agglomeration of amorphous MoS2 and maintaining the whole structural stability, by building nanosized amorphous MoS2 coated on carbon microtubes, so as to obtain an anode material with excellent lithium ion battery (LIBs) performances. More importantly, the amorphous MoS2 provides percolation pathways through the opening of active diffusion channels, expediting the diffusion rate of lithium ions. Furthermore, the composite paper as a whole is favorable for increasing the overall conductivity and energy density of the anode material without binders. As a result, when used as anode materials for half and full cell LIBs, N-doped carbon microtubes@amorphous MoS2 delivers an ultra-long cycling life, high reversible capacities and superior rate performances.

Sodium-ion batteries (SIBs) have attracted intense scientific attention as the most promising next generation energy storage device. However, the large-scale practical application of SIBs has been limited by exploring a low-cost and high performance anode material. Herein, hard carbon microfibers are successfully synthesized from renewable paper via simply carbonization procedure and proposed as anode materials for SIBs. The optimized carbonization at 1400 °C endows hard carbon microfibers high reversible charge capacity of 319.6 mAh g−1, good rate capability as well as excellent cycle life with capacity retention of 99.3% after 100 cycles. The sodium storage mechanism is further investigated by virtue of various technologies, indicating that sodium ions are stored in inter- and intra-layers. Remarkably, a full cell with the as-prepared anode and a Na3V2(PO4)3 cathode shows a favorable capacity of 243.8 mAh g−1 and stable cyclability of 218.9 mAh g−1 after 100 cycles. This study provides an opportunity for a cost-effective and renewable anode material for SIBs.

The self-standing electrode materials with large surface area and high electronic conductivity have attracted intensive attention in energy storage devices. Herein, the expanded graphite paper (EGP) is fabricated via a controlled cathodic expansion in acetonitrile with tetrabutylammonium bromide at 10 V. The as-prepared EGP exhibits a three-dimensional porous structure with large specific surface area and high electronic conductivity, which is a favorable support for in situ growing nickel cobalt carbonate hydroxide (NiCo-CH) nanowires via a simple hydrothermal method. The as-prepared NiCo-CH@EGP composite achieves high areal capacity of 2.55 C cm−2 at 0.5 mA cm−2, and still remains 1.38 C cm−2 even at 60 mA cm−2. The assembled NiCo-CH@EGP//activated carbon asymmetric supercapacitor exhibits the maximum energy density of 0.30 mWh cm−2 at a power density of 0.92 mW cm−2, and a suitable cyclic stability with the capacity retention of 78.1 % after 10,000 cycles at 20 mA cm−2. The results indicate that the self-standing NiCo-CH@EGP is a potential electrode material for energy storage devices.

Hollow nickel hydroxide microspheres built of nanosheets could be obtained by hydrothermal synthesis in the presence of glycine. After heating to 400 °C in air, the hexagonal β-Ni(OH)2 was converted into cubic NiO which showed better electrical conductivity and greater surface area compared with other annealing temperatures. The surface morphology remained almost unchanged, while the Ni(OH)2 nanosheets with solid interior were changed into NiO nanosheets composed of interconnected nanoparticles and mesopores after annealing at 400 °C. The sulfur-filled hollow mesoporous NiO microspheres obtained after annealing at 400 °C was loaded into the carbon paper as cathode (NiO/S) for lithium-sulfur batteries. The NiO/S cathode could deliver a large specific capacity of 1300 mAh g−1 at 0.2C (335 mA g−1), much greater than bare sulfur loaded into the carbon paper (1000 mAh g−1). Moreover, the NiO/S cathode showed superior capacity recovery after C-rate test and coulombic efficiency during cycling test than S cathode. The improved performance for NiO/S could be attributed to the conductive NiO microspheres with mesoporous nanosheets that provided intimate electrical contact for boosting the charge-transfer reaction between lithium ions and sulfur materials, limited the polysulfide shuttle, and buffered volumetric expansion/contraction during charging and discharging.

An in-situ and controllable redox deposition method has been applied to prepare binder-free MnO2 nanosheet array-decorated carbon paper as negative electrode for vanadium redox flow batteries (VRFB). Electrochemical performance of electrode depends on amount and uniform distribution of MnO2 on carbon paper, which were controlled by solution pH, KMnO4 concentration, and deposition time. Modified carbon paper (CPA-05-30) with a uniform MnO2 nanosheet coating layer was obtained in 0.05 M KMnO4 + 0.5 M H2SO4 solution for 30 min. CPA-05-30 presents the most excellent electrocatalytic performance for V3+/V2+ redox reaction. On CPA-05-30, charge transfer and diffusion processes for V3+/V2+ redox reaction are accelerated as a result of MnO2 nanosheet with high catalytic activity and excellent hydrophilcity. Therefore, loading MnO2 on carbon paper improves electrochemical activity V3+/V2+ redox reaction. Moreover, in charge-discharge test, the cell using CPA-05-30 as negative electrode shows higher discharge capacity and better capacity retention at 50 mA cm−2 for 50 cycles in comparison with pristine cell. It indicates that MnO2 nanosheet can efficiently increase electrolyte utilization. At 100 mA cm−2, energy efficiency of the cell using CPA-05-30 is 66.4%, which is 6.0% higher than that of pristine cell. MnO2 nanosheet decorated carbon paper shows excellent electrochemical properties for energy storage application, which evidences its potential application in VRFB.

Tetrathiafulvalene (TTF) based charge-transfer compounds are ideal as a transducer layer for a solid-contact ion-selective electrode (SC-ISE), because of their excellent ionic conductivity and high capacitance. Since nanomaterials with tailored geometries exhibit unique shape-dependent properties and subsequent utilization of them for the fabrication of electrochemical devices is of significant interest. Gold-TTF (Au-TTF) with different morphologies such as flower-like, sheet-like, long wire and tubular with different length, were synthesized by microfluidics-dictated synthesis in a fast, simple and continuous procedure. The electrochemical performance of synthesized Au-TTF hybrid crystals was characterized by cyclic voltammetric, electrochemical impedance and constant-current chronopotentiometric measurement. The results demonstrate that long-tubular-like Au-TTF crystal is best suitable for ISE due to its great stability, high capacitance and co-existence of TTF/TTF+ providing a stable interphase potential. Then paper-based potentiometric potassium sensors were fabricated based on flower-like and long-tubular-like Au-TTF hybrid crystal as transducer layer of ISE and reference electrode. Compared to paper-based sensor with flower-like Au-TTF as transducer layer, paper-based sensor with long-tubular-like Au-TTF as transducer layer exhibits a much better Nernstian response with a slop of 57.64 ± 0.09 mV/dec and a lower detection limit of 2.75 × 10−6 M. Furthermore, the fabricated potentiometric sensor requires only 5 μL samples to test and displays little water-layer, good anti-interference, and great reproducibility and selectivity.

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 VO2+/VO2+ and V2+/V3+ 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.

The exploration of high-performance and low-cost electrocatalysts for catalyzing both hydrogen and oxygen evolution reaction (HER and OER) at high current density is of vital significance for the commercialization of water splitting. Herein, amorphous NiFe phosphides are electrodeposited on 3D nanoarray-structured nitrogen-doped carbon paper (NCP) for direct use as a hybrid electrode toward overall water splitting. The as-prepared NiFe-P/NCP electrode requires only an overpotential of 0.226 and 0.125 V at 50 mA cm–2 for OER and HER, respectively. In addition, NiFe-P/NCP electrodes are further measured as a catalytic cathode and anode couple (NiFe-P/NCP||NiFe-P/NCP) for overall water splitting, exhibiting a low cell voltage of 1.547 to reach 10 mA cm–2 as well as a long-term durability. Our work reveals the significance of introducing well-designed substrate and bimetallic active species for enhanced electrochemical performance towards overall water splitting.

Plasmas techniques are novel routes for the preparation of complex nanostructured materials for catalysis and clean hydrogen energy such as fuel cells. CBPLD technique allows enhanced interaction between the catalyst and the support and improved catalytic properties. Herein, a highly active and durable vertically aligned nanostructured shrub-like bimetallic PtxRh100-x alloys with atomic ratios close to nominal values are grown on carbon paper substrate. The tolerance to CO poisoning and ethanol electrooxidation reactions are studied over these new types of shrub-like bimetallic PtxRh100-x/CP catalysts, demonstrating that such structures effectively facilitate both processes and very low long-term poisoning rates. Such high catalytic activity accounts for two mechanisms: Rh a highly oxophilic transition metal activates water dissociation at lower potentials than Pt (bifunctional mechanism), and the ligand effect where Rh alters the electronic structure of the neighboring Pt suggesting a faster supply in OHads.

Tin oxide/Multi Walled Carbon nano tube nanocomposite (SnO 2 /MWCNT) is synthesized using ethylene glycol mediated industrially viable simple process. Binder free, self-supporting and flexible SnO 2 /MWCNT nanocomposite paper has been prepared by employing the vacuum filtration technique. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy (RS), and thermal gravimetric analysis (TGA) to evaluate the structure of anode and tested for its performance in a Lithium rechargeable cell. Electrochemical measurements demonstrate that the SnO 2 /MWCNT composite paper anode with 30% of SnO 2 by weight delivers a specific discharge capacity of ∼420 mAh g −1 up to the investigated 50 cycles at a current density of 100 mA g −1 which is ∼200 % increase in capacity as compared to pristine MWCNT anode tested under similar conditions. The application of the developed anode is demonstrated by fabricating a lithium ion pouch cell.