Porous Electrodes Research Articles

Investigation of the Single-Particle Scale Structure-Activity Relationship Providing New Insights for the Development of High-Performance Batteries.

As electric vehicles, portable electronic devices and tools have increasingly high requirements for battery energy density and power density, constantly improving battery performance has become a research focus. Accurate measurement of the structure-activity relationship of active materials is the key to advancing the research of high-performance batteries. However, the conventional performance tests of active materials are based on the electrochemical measurement of porous composite electrodes containing active materials, polymer binders, and conductive carbon additives, which cannot establish an accurate structure-activity relationship with the physical characterization of microregions. In this review, in order to promote the accurate measurement and understanding of the structure-activity relationship of materials, the electrochemical measurement and physical characterization of energy storage materials at single-particle scale are reviewed. The potential problems and possible improvement schemes of the single particle electrochemical measurement and physical characterization are proposed. Their potential applications in single particle electrochemical simulation and machine learning are prospected. This review aims to promote the further application of single particle electrochemical measurement and physical characterization in energy storage materials, hoping to achieve three-dimensional unified evaluation of physical characterization, electrochemical measurement, and theoretical simulation at the single particle scale to provide new inspiration for the development of high-performance batteries. This article is protected by copyright. All rights reserved.

Surfactant Effects in Porous Electrodes for Microemulsion Redox Flow Batteries

Abstract The effect of surfactant additives on electrochemical behavior in porous electrodes was investigated using vanadium redox flow battery half-cells and the dependence of volumetric kinetics and mass transport on electrolyte, surfactant, and electrode type was explored. Without surfactant added, carbon paper electrodes demonstrated greater kinetics and transport compared to carbon felt, for a given electrolyte. Additionally, posolyte kinetics are greater than negolyte kinetics by one to three orders of magnitude, depending on the electrode type. Addition of surfactant increased electrode wettability and possibly electrochemical surface area. However, this was accompanied by a decrease in volumetric mass transport, due to stronger electrolyte-electrode interactions. The presence of sodium dodecyl sulfate (SDS) influenced posolyte and negolyte kinetics differently. Kinetics showed a dependence on electrode type and surfactant. On carbon felt, volumetric kinetics decreased for both posolyte and negolyte with SDS addition. On carbon paper, SDS decreased volumetric kinetics for the posolyte but increased (>2X) kinetics for the negolyte! This kinetic enhancement depends on surfactant chemistry: cetyltrimethylammonium bromide, a cationic surfactant, failed to increase kinetics. Furthermore, SDS did not increase areal specific resistance. These findings show the superior performance of carbon paper compared to carbon felt and suggest SDS as a possible VRFB negolyte additive

Correlating Electrolyte Infiltration with Accessible Surface Area in Macroporous Electrodes using Neutron Radiography

Abstract Carbon-based porous electrodes are commonly employed in electrochemical technologies as they provide a high surface area for reactions, an open structure for fluid transport, and enable compact reactor architectures. In electrochemical cells that sustain liquid electrolytes (e.g., redox flow batteries, CO2 electrolyzers, capacitive deionization), the nature of the interaction between the three phases - solid, liquid and gas - determines the accessible surface area for reactions, which fundamentally determines device performance. Thus, it is critical to understand the correlation between the electrolyte infiltration in the porous electrode and the resulting accessible surface area in realistic reactor architectures. To tackle this question, here we simultaneously perform neutron radiography with electrochemical measurements to correlate macroscopic electrode saturation/wetting with accessible surface area. We find that for untreated electrodes featuring neutral wettability with water, the electrode area remains underutilized even at elevated flow rates, both for interdigitated and parallel flow fields. Conversely, increasing the electrode hydrophilicity results in an order-of-magnitude increase in accessible surface area at comparable electrode saturation, and is less influenced by the electrolyte flow rate. Ultimately, we reveal useful correlations between reactor architectures and electrode utilization and provide a method that is broadly applicable to flow electrochemical reactors.

Briefing: Selective laser sintering technology to print walnut shell/phenolic resin new biomass-based porous electrode

In this paper, porous carbon electrodes were prepared by using walnut shell and phenolic resin as matrix materials, combined with selective laser sintering (SLS) technology and carbonization process. The effects of different ratios and temperatures on the macroscopic morphology, graphitization degree, electrical conductivity and pore structure of the carbonized parts were investigated. The results show that the lower proportion of walnut shell and the higher carbonization temperature increase the degree of graphitization. High temperature has a significant effect on the conductivity. The conductivity at 1000 °C is 7.5197 S·cm−1, which is 752 % higher than that at 600 °C, while the conductivity at 30 % walnut shell content is only 75.4 % higher than that at 50 %. This study provides a new reference for the preparation of carbon electrodes with complex shape and structure by biomass consumables.

Enhancing power and energy densities of supercapacitors with slit porous carbon electrodes by playing with pore width and ion shapes

The energy and power performances of double-layer supercapacitors can be affected by pore size, the nature of the electrolyte, and electrode–electrolyte interaction. We performed molecular dynamics simulations of mixtures of ionic liquids confined into slit-shaped carbon electrodes with pores of 0.75 and 1.5nm under applied voltage to investigate the interplay of pore size, and ion shape to the performance of supercapacitor. Inside the pores of 1.5nm the ions are organized into two layers, and a single layer inside the pore of 0.75nm. The tetramethylammonium cations ([TMA]+) is steric hindered to fill the pores of 0.75nm that can be only filled by 1-ethyl-3-methyl-imidazolium cations ([EMIM]+) and bis(trifluoromethanesulfonyl)imide anions ([NTf2]−). The increase of [TMA][NTf2] in the mixtures results in small pores with a decreased density of ions or empty at the non-charged state of the electrode. Upon the application of voltage, these empty or partially filled pores have only the adsorption of counter ions, which are responsible for the best performance of mixtures with mole fraction of [TMA]+ equals to 0.25 and 0.75.

Gold nanostructure-enhanced immunosensing: ultra-sensitive detection of VEGF tumor marker for early disease diagnosis

We present an advanced electrochemical immunosensor designed to detect the vascular endothelial growth factor (VEGF) precisely. The sensor is constructed on a modified porous gold electrode through a fabrication process involving the deposition of silver and gold on an FTO substrate. Employing thermal annealing and a de-alloying process, the silver is eliminated from the electrode, producing a reproducible porous gold substrate. Utilizing a well-defined protocol, we immobilize the heavy-chain (VHH) antibody against VEGF on the gold substrate, facilitating VEGF detection through various electrochemical methods. Remarkably, this immunosensor performs well, featuring an impressive detection limit of 0.05 pg/mL and an extensive linear range from 0.1 pg/mL to 0.1 µg/mL. This emphasizes it’s to measure biomarkers across a wide concentration spectrum precisely. The robust fabrication methodology in this research underscores its potential for widespread application, offering enhanced precision, reproducibility, and remarkable detection capabilities for the developed immunosensor.

Mathematical Model for a Lithium-Ion Battery with a SiO/Graphite Blended Electrode Based on a Reduced Order Model Derived Using Perturbation Theory

Abstract Silicon oxide (SiO) is a promising anode material for high-energy lithium-ion batteries, as it is made from low-cost precursors, has a potential close to that of Li, and has high theoretical specific capacity. However, the applications of SiO are limited by the intrinsic low electrical conductivity, large volume change, and low coulombic efficiency, which often lead to poor cycling performance. A common strategy to address these shortcomings is to blend SiO with graphite active materials to form a composite anode for better capacity retention. In this work, we derive a reduced order model (ROM1) using perturbation theory. We employ the multi-site, multi-reaction (MSMR) framework of a composite porous electrode blend consisting of two lithium-host materials, SiO and graphite. The ROM1 model employs a single-particle model (SPM) approach as the leading-order solution and involves the numerical analysis of a single, nonlinear partial differential equation for each host material that describes diffusion by means of irreversible thermodynamics, wherein chemical-potential gradients are the driving forces for the diffusion. The first-order correction treats losses other than that of the SPM.

Boosting Electrochemical CO2 Reduction to CO by Regulating the Porous Structure of Carbon Membrane.

Ni single-atom-decorated nitrogen-doped carbon materials (Ni-Nx-C) have demonstrated high efficiency in the electrochemical reduction of CO2 (CO2RR) to CO. In this study, Ni-Nx-C active sites were embedded within a carbon membrane via an electrospinning and pyrolysis process. The resulting self-supported carbon membrane hosting Ni-Nx-C sites could be directly utilized as an electrode for the CO2RR. To enhance the CO2RR performance of the carbon membrane, the porous structure of the carbon membrane was fine-tuned by incorporating a pore-forming agent. The optimized porous carbon membrane electrode, K0.66-Ni-NC, achieved an impressive CO faradaic efficiency (FECO) of over 90% within a wide potential range from -0.8 to -1.6 V vs RHE for CO2RR. Additionally, it maintained an FECO of above 90% at -0.8 V vs RHE throughout a 30 h durability test in an H-cell. Further analysis has revealed that the porous structure of the carbon membrane not only facilitates the mass transport of CO2 but also increases the level of exposure of active sites during the CO2RR.

Iodine intercalation-assisted alkali activation constructs coal-based porous carbon for high-performance supercapacitors

Supercapacitors have the advantages of fast charging and discharging speeds, high power density, long cycle life, and wide operating temperature range. They are widely used in portable electronic equipment, rail transit, industry, military, aerospace, and other fields. The design and preparation of low-cost, high-performance electrode materials still pose a bottleneck that hinders the development of supercapacitors. In this paper, coal was used as the raw material, and the coal-based porous carbon electrode material was constructed using the iodine intercalation-assisted activation method and used for supercapacitors. The CK-700 electrode exhibits excellent charge storage performance in a 6 M potassium hydroxide (KOH) electrolyte, with a maximum specific capacitance of 350 F/g at a current density of 0.5 A/g. In addition, it has an excellent rate performance (310 F/g at 1 A/g) and cycle stability (capacitance retention up to 91.7 % after 30000 cycles). This work provides a method for realizing high-quality, high-yield and low-cost preparation of coal-based porous carbon, and an idea for improving the performance of supercapacitors.

Copper Oxide Nanoparticles Anchored on Porous Carbon Nitride Nanosheets for Supercapacitor Applications

Electrochemical energy storage devices are vital for renewable energy integration and the deployment of electric vehicles. Ongoing research seeks to create new materials with innovative morphologies capable of delivering high specific capacitance for the next generation of customizable energy devices. Carbon nitride is an excellent candidate for electrochemical energy storage devices; however, it has limitations such as layer stacking, poor electric conductivity, a restricted number of electroactive sites, and static electrochemical reaction rates. This research objective is to make porous structures in carbon nitride nanosheets and integrate them with CuO particles to increase surface area and improve electrochemical performance. The use of thermal heating, acidic treatment, and hydrothermal processes accomplishes this. Along with X-ray diffraction peaks of the CuO phase, a prominent peak (002) at 27.67° indicates the presence of graphitic-structured carbon nitride. TEM images show that CuO particles are evenly attached to the surface of g-C3N4 nanosheets with lattice intervals of 0.336 and 0.232 nm, which are the (002) and (111) orientations of the g-C3N4 and CuO phases, respectively. Adding CuO nanoparticles to porous g-C3N4 nanosheets avoids layer stacking and provides micro- and mesopore channels, increasing the specific surface area (42.60 m2 g-1). The CuO@ porous g-C3N4 electrode delivered 817 F g-1 of specific capacitance at 1 A g-1 and admirable capacitance retention (92.3% after 6000 cycles) due to the synergistic impact of its unique composition and structural characteristics. Because of its outstanding electrochemical performance and fascinating discoveries, CuO@ porous g-C3N4 may be employed as a cathode material for high-performance supercapacitors.

High Temperature Solid Oxide Electrolyte Fuel Cell Formulation: Non-Steady State Utilization of Fuel and Oxidant

The formulation presented in this paper was developed with the objective of its application to investigate the transient behavior of a high temperature solid oxide fuel cell (SOFC); especially with respect to the non-steady state consumption of fuel and oxidant reactants. Specifically, the chemical species transient amounts, their mole fractions, and total pressures in the cell anode-side fuel- (hydrogen) and cathode-side oxidant- (oxygen of the air) chambers can be predicted under the isothermal condition at a fixed cell-current level. The developed formulation is also capable of predicting the transient mole fraction profiles of fuel (hydrogen) and oxidant (oxygen) in the cell porous anode and cathode, respectively; thus, providing insight into the reactant species' effective transport and their utilization, via electrochemical reactions, in the cell porous electrodes. The presented formulation can be adapted for any fuel and oxidant combinations in any high temperature SOFC.

Self-discharge in flowless Zn-Br2 batteries and its mitigation

Several decades after the invention of the flow Zn-Br2 systems persistent attempts have been made to develop stationary Zn-Br2 batteries. Such development should increase the energy density of the system simultaneously significantly reducing their cost and opening new challenges associated with the cell design and its performance. One of the major concerns is the rapid self-discharge of stationary systems leading to spontaneous charge loss during battery storage time. While self-discharge in flow cells is generally attributed to the chemical oxidation of the Zn anode, we show that the origin of self-discharge in a static configuration is completely different. By systematic investigations of activated carbon with different surface areas under varied charging conditions, mechanistic insights into this phenomenon were provided. Based on this understanding, we proposed herein an effective way to suppress the cathode's self-discharge by encapsulation of a bromine complexing agent inside the electrode's pore matrix. The modified electrodes unveil unique chemical kinetics of deaggregation of the stable fuse salt phase composed of bromine complexing agent and Br3− anions upon discharging. To the best of our knowledge, such a phenomenon has not been reported yet. The proposed system demonstrates high capacity (up to 300mAh/g) and impressive long-term stability.

Biomass waste derived from cassia fistula into value-added porous carbon electrode for aqueous symmetric supercapacitors

Activated carbon derived from biomass sources has been renowned as one of the key materials and economical precursors for numerous energy conversion and storage applications. Herein, we utilized a less explored Cassia fistula (Pulp and seed) biomass as the carbon source for supercapacitor application. Further, a less toxic and low activation method has been implemented to activate the biomass-derived carbon. The highly dense seed resulted in better porous compared to the pulp source. The electrochemical performances of the bio-carbon electrodes have been examined by CV, GCD, and EIS studies. The activated carbon derived from the Cassia fistula seed (CFSA) electrode achieved a specific capacitance value of 136.5 Fg−1 at 0.5 Ag−1 in 3 M KOH. Moreover, the electrode demonstrates an extremely long stability by sustaining 98 % of initial capacitance after 10,000 cycles, which signifies the robust electrochemical stability behavior of the obtained electrode. Further, the aqueous symmetric supercapacitor achieved a maximum energy and power density of 7.2 WhKg−1 and 3488.1 WKg−1, respectively. Likewise, after 10,000 stability cycles, the cell retains 96.4 % capacitance at 5 Ag−1 which denotes the noteworthy capacitive behaviour of the CFSA electrode. Thus, the present work suggests an eco-friendly resource for developing an effectual carbon electrode for energy storage applications.

ZIF-8-derived N-doped porous carbon electrodes enabled with in situ embedded ZrO2 nanoparticles for phosphorus removal

Excessive phosphorus discharges are not favorable to the normal functioning of water ecosystems. Although some treatments have been implemented to control phosphorus concentrations in sewage, several challenges remain for them. Capacitive deionization technology (CDI) possesses excellent potential for phosphorus removal, and the electrode material is the key to CDI. Herein, a novel ZIF-8-derived N-doped porous carbon electrode enabled with in situ embedded ZrO2 nanoparticles (ZNPC) was fabricated through a simple in-situ growth approach. The experimental results demonstrate that ZrO2 embedded in ZNPC can improve the electrochemical performance and provide suitable affinity sites for phosphorus, thus enhancing the electrode performance in capturing phosphorus. Isothermal and kinetic models were adopted to investigate the phosphorus uptake process. Mechanism analysis reveals that the phosphorus removal behavior is associated with the electric field, ligand exchange, and electrostatic attraction. This study provides a promising approach for facile constructing Zr-based N-doped porous carbon and expands its potential utility for phosphorus removal from aqueous solutions.

Rapid Fabrication of Binder Free Nickel Cobalt Oxide Electrodes with Forest-Like Architecture for Electrochemical Energy Storage Applications

A rapid and facile technique to synthesize nickel cobalt oxide electrodes by photothermal treatment of mixed organometallic precursor solution is reported. Using short and intense pulses of light from a xenon flash lamp, spray coated films are converted into porous nickel cobalt oxide electrodes with forest-like architecture. The electrode films fabricated in a few seconds show excellent energy storage properties as supercapacitor electrodes. Specific capacitance of up to 116 Fg-1 and capacitance retention of up to 75% were observed in samples with low mass loading. Analysis of the cyclic voltammetry (CV) curves shows that capacitance is the dominating charge storage mechanism in these films. To study the effect of varying the mass loading in electrodes, double and triple layered electrodes were also studied. In films with high mass loading, the specific capacitance of the films decreased but areal capacitance continued to increase. A high areal capacitance of up to 243 mFcm-2 is observed in films with high mass loading. CV curve analysis of high mass loading electrodes further shows that in films with higher mass loading, the charge storage mechanism is a mix of capacitance and diffusion processes. The contribution of diffusion process increased with increase in the mass loading of the electrodes. This study sheds light into the mechanism of charge storage in electrodes prepared by large scale amenable single step process of photonic curing which could be utilized to fabricate electrodes in industrial scale.

High-performance electrosorption of lanthanum ion by Mn3O4-loaded phosphorus-doped porous carbon electrodes via capacitive deionization

Transition-metal-oxide@heteroatom doped porous carbon composites have attracted considerable research interest because of their large theoretical adsorption capacity, excellent electrical conductivity and well-developed pore structure. Herein, Mn3O4-loaded phosphorus-doped porous carbon composites (Mn3O4@PC-900) were designed and fabricated for the electrosorption of La3+ in aqueous solutions. Due to the synergistic effect between Mn3O4 and PC-900, and the active sites provided by Mn–O–Mn, C/PO, C–P–O and Mn–OH, Mn3O4@PC-900 exhibits high electrosorption performance. The electrosorption value of Mn3O4@PC-900 was 45.34% higher than that of PC-900, reaching 93.02 mg g−1. Moreover, the adsorption selectivity reached 87.93% and 89.27% in La3+/Ca2+ and La3+/Na+ coexistence system, respectively. After 15 adsorption-desorption cycles, its adsorption capacity and retention rate were 50.34 mg g−1 and 54.12%, respectively. The electrosorption process is that La3+ first accesses the pores of Mn3O4@PC-900 to generate an electric double layer (EDL), and then undergoes further Faradaic reaction with Mn3O4 and phosphorus-containing functional groups through intercalation, surface adsorption and complexation. This work is hoped to offer a new idea for exploring transition-metal-oxide @ heteroatom doped porous carbon composites for separation and recovery of rare earth elements (REEs) by capacitive deionization.

A universal three-dimensional hydrogel electrode for electrochemical detection of SARS-CoV-2 nucleocapsid protein and hydrogen peroxide

Coronavirus disease 2019 (COVID-19) is a highly contagious illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), resulting in a global health crisis. The primary diagnostic method for COVID-19 is quantitative reverse transcription PCR, which is time-consuming and requires expensive instrumentation. Here, we developed an electrochemical biosensor for detecting SARS-CoV-2 biomarkers using a 3D porous polyacrylamide/polyaniline hydrogel (PPG) electrode prepared by UV photopolymerization and in situ polymerization. The electrochemical immunosensor for detecting SARS-CoV-2 N protein via the immune sandwich principle demonstrated a lower detection limit of 42 pg/mL and comparable specificity to commercial enzyme-linked immunosorbent assay, which was additionally validated in pseudoviruses. The electrochemical sensor for hydrogen peroxide showed a low detection limit of 0.5 μM and excellent selectivity, which was further confirmed in cancer cells under oxidative stress. The biomarkers of SARS-CoV-2 were successfully detected due to the signal amplification capability provided by 3D porous electrodes and the high sensitivity of the antigen-antibody specific binding. This study introduces a novel three-dimensional electrode with great potential for the early detection of SARS-CoV-2.

Asymmetric Supercapacitors Based on ZnCo2O4 Nanohexagons and Orange Peel Derived Porous Carbon Electrodes.

Herein, the performance of asymmetric supercapacitors (ASC) fabricated using ZnCo2O4 (ZCO) nano-hexagons and orange peel-derived activated carbon (OPAC) as electrodes was studied. ZCO was prepared by a double hydroxide method and OPAC was prepared from orange peel followed by KOH activation. For ZCO, the calcination temperature was determined using TGA analysis. The XRD showed the presence of a cubic spinel structure. The chemical structure was analyzed using XPS, FTIR, and Raman spectroscopy respectively. For OPAC, the presence of an amorphous nature was inferred; FTIR and Raman studies indicate the presence of functional groups and defect structure in the material. The presence of ZCO nano-hexagons was observed from SEM and TEM respectively. For OPAC, an interconnected pore structure was observed from the SEM image. The specific capacitance for ZCO and OPAC was found to be 194 F.g-1 and 159 F.g-1 at a current density of 0.25 A.g-1. Further, an ASC was fabricated using ZCO as a positive and OPAC as a negative electrode in 2M KOH-soaked separator. A cell voltage of 1.2 V was achieved and the specific capacitance was calculated to be 64 F.g-1 at 0.25 A.g-1. Further, the cyclic stability and the changes at the electrode/electrolyte interface were studied.

Condensed Layer Deposition of Nanoscopic TiO2 Overlayers on High-Surface-Area Electrocatalysts.

Encapsulating an electrocatalytic material with a semipermeable, nanoscopic oxide overlayer offers a promising approach to enhancing its stability, activity, and/or selectivity compared to an unencapsulated electrocatalyst. However, applying nanoscopic oxide encapsulation layers to high-surface-area electrodes such as nanoparticle-supported porous electrodes is a challenging task. This study demonstrates that the recently developed condensed layer deposition (CLD) method can be used for depositing nanoscopic (sub-10 nm thick) titanium dioxide (TiO2) overlayers onto high-surface-area platinized carbon foam electrodes. Characterization of the overlayers by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) showed that the films are amorphous, while X-ray photoelectron spectroscopy confirmed that they exhibit TiO2 stoichiometry. Electrodes were also characterized by hydrogen underpotential deposition (Hupd) and carbon monoxide (CO) stripping, demonstrating that the Pt electrocatalysts remain electrochemically active after encapsulation. Additionally, copper underpotential deposition (Cuupd) measurements revealed that TiO2 overlayers are effective at blocking Cu2+ from reaching the TiO2/Pt buried interface and were used to estimate that between 43 and 98% of Pt surface sites were encapsulated. Overall, this study shows that CLD is a promising approach for depositing nanoscopic protective overlayers on high-surface-area electrodes.

Surprising Route to a Monoazaporphyrin and Full Characterization of Its Complexes with Five Different 3d Metals.

In the search for mild agents for the oxidative cyclization of tetrapyrromethane to the corresponding corrole, we discovered a route that leads to a monoazaporphyrin with three meso-CF3 groups. Optimization studies that allowed access to appreciable amounts of this new macrocycle paved the way for the preparation of its cobalt, copper, nickel, zinc, and iron complexes. All complexes were fully characterized by various spectroscopic methods and X-ray crystallography. Their photophysical and electrochemical properties were determined and compared to those of analogous porphyrins in order to deduce the effect of the peripheral N atom. Considering the global efforts for designing efficient alternatives to platinum group metal (PGM) catalysts, they were also absorbed onto a porous carbon electrode material and studied as electrocatalysts for the oxygen reduction reaction (ORR). The cobalt complex was found to be operative at a quite positive catalytic onset potential and with good selectivity for the desirable 4-electrons/4-protons pathway.