Reactive Surface Area Research Articles

An effect of nano alumina and nano titanium di oxide with polypropylene fiber on the concrete: mechanical and durability study

For a long time, researchers have worked to improve the qualities of cement-based mixes. Because of their small size, strong reactivity, and huge surface area, nanoparticles are becoming more and more regarded as one of the greatest substitutes for cement because of their capacity to increase durability and strength. This work presents the results of an experimental investigation into the strength and durability properties of fiber-reinforced concretes with polypropylene (PP) fibers added to the concrete by volume and nano Al2O3 and nano TiO2 are used as partial substitutes for cement. Nano Al2O3 and nano TiO2 particles used ranged in size from 30 to 300 nm. The specimens were cast using cement blended nano Al2O3 and nano TiO2 percentages of 1%, 2%, 3%, and 4% by weight of cement. M55 grade concrete was employed for the casting process. The addition of PP fibers to the concrete was 0.5% by volume. The specimens underwent a battery of mechanical tests, including microstructural testing, compression testing, split tensile strength testing, and rupture modulus testing. Furthermore, tests for durability factors such as porosity, sorptivity, and degradation were conducted, and the findings are presented. By comparing the outcomes, it was shown that the inclusion of 0.5% PP fibers and 2% nano Al2O3 or nano TiO2 improved the mechanical qualities, but a decrease followed this in strength. The findings demonstrated that 2% nano Al2O3 combined with 0.5% PP fiber had a greater mechanical strength than 2% nano TiO2.

Graft copolymerization of carboxymethylcellulose with solketal acrylate

The objective of this work is to synthesize new materials based on cellulose fiber. In this study, we presented the synthesis of a new biomaterial by conducting graft polymerization of 2,2-dimethyl-1,3-dioxolan-4-yl methyl acrylate (DMDMA solketal acrylate) onto carboxymethylcellulose (CMC), using KPS as an initiator. We conducted several experiments to determine the optimal conditions for preparing this biopolymer, varying the reaction time and the ratio between the initiator and the monomer. The results revealed that the highest grafting yield, 52%, was obtained after 72 min at 65 °C, with 6.26 mmol of KPS/eq OH and 4.43 moles of DMDMA/eq OH, using THF as a solvent. FTIR spectroscopy confirmed the grafting of monomers onto the CMC. Thermogravimetry showed that the degradation of the grafted CMC occurs in two stages, unlike the degradation of the CMC, which occurs in a single stage, confirming the modification of the starting product. SEM images clearly show the morphological difference between the CMC and the grafted CMC. The BET analysis reveals moderate adsorption at low pressure, followed by a marked increase at high pressure, indicating the presence of mesopores. The hysteresis between adsorption and desorption also suggests closed pore structures. The pore size distribution shows a predominance of pores between 30 and 100 Å, providing an optimal specific surface area for small molecule adsorption and catalytic reactions. This mesoporous profile is suitable for adsorption and catalysis applications. To our knowledge, our study represents the first use of the synthesized monomer, DMDMA solketal acrylate, for grafting onto the structure of CMC, highlighting the originality of our research.

Graphene Supported NiFe-LDH and PbO2 Catalysts Prepared by Plasma Process for Oxygen Evolution Reaction.

The development of efficient catalysts for water electrolysis is crucial for advancing the low-carbon transition and addressing the energy crisis. This work involves the fabrication of graphene-based catalysts for the oxygen evolution reaction (OER) by integrating NiFe-LDH and PbO2 onto graphene using plasma treatment. The plasma process takes only 30 min. Graphene's two-dimensional structure increases the available reaction surface area and improves surface electron transport. Plasma treatment further improves catalyst performance by facilitating nanoparticle attachment and creating carbon defects and sulfur vacancies. Density functional theory (DFT) calculations at the PBE provide valuable insights into the role of vacancies in enhancing catalyst performance for OER. The catalyst's conductivity and electronic structure are greatly impacted by vacancies. While modifications to the electronic structure increase the kinetics of charge transfer, the vacancy structure can produce more active sites and improve the adsorption and reactivity of OER intermediates. This optimization of intermediate adsorption and electronic properties leads to increased overall OER activity. The catalyst NiFe-PbO2/S/rGO-45, synthesized through plasma treatment, demonstrated an overpotential of 230 mV at 50 mA·cm-2 and a Tafel slope of 44.26 mV dec-1, exhibiting rapid reaction kinetics and surpassing the OER activity of commercial IrO2. With its excellent performance, the prepared catalyst has broad prospects in commercial applications such as water electrolysis and air batteries.

Highly Porous 3D Ni-MOFs as an Efficient and Enzyme-Mimic Electrochemical Sensing Platform for Glucose in Real Samples of Sweat and Saliva in Biomedical Applications.

Nickel-based metal-organic frameworks, denoted as three-dimensional nickel trimesic acid frameworks (3D Ni-TMAF), are gaining significant attention for their application in nonenzymatic glucose sensing due to their unique properties. Ni-MOFs possess a high surface area, tunable pore structures, and excellent electrochemical activity, which makes them ideal for facilitating electron transfer and enhancing the catalytic oxidation of glucose. This research describes a new electrochemical enzyme-mimic glucose biosensor in biological solutions that utilizes 3D nanospheres Ni-TMAF created layer-by-layer on a highly porous nickel substrate. The Ni-TMAF based on the nonenzymatic electrochemical glucose oxidation represent the promising approach, leveraging the unique properties of Ni-TMAF to provide efficient, stable, and potentially more cost-effective alternatives to traditional enzyme-mimic sensors. The MOF is synthesized from trimesic acid (TMA) and nickel nitrate hexahydrate through a solvothermal reaction process. The resulting Ni-TMAF utilizes the three-dimensional nanospheres of crystalline porous structure with a large surface area and numerous active sites for catalytic reaction toward glucose. Ni-TMAF are indeed known for their excellent electrocatalytic activity, particularly in the context of glucose oxidation under alkaline conditions. The nickel centers in the Ni-TMAF facilitate efficient electron transfer and redox reactions, leading to the high sensitivity of 203.89 μA μM-1 cm-2 and lower LOD of 0.33 μM and fast response time of <3 s in glucose sensors. Their stability, cost-effectiveness, and high performance make 3D Ni-TMAF a promising material for nonenzymatic electrochemical glucose sensors.

Upcycling Waste Cotton Cloth into a Carbon Textile: A Durable and Scalable Layer for Vanadium Redox Flow Battery Applications

In our investigation, we unveil a novel, eco-friendly, and cost-effective method for crafting a bio-derived electrode using discarded cotton fabric via a carbonization procedure, marking its inaugural application in a vanadium redox flow battery (VRFB). Our findings showcase the superior reaction surface area, heightened carbon content, and enhanced catalytic prowess for vanadium reactions exhibited by this carbonized waste cloth (CWC) electrode compared to commercially treated graphite felt (TT-GF). Therefore, the VRFB system equipped with these custom electrodes surpasses its treated graphite felt counterpart (61% at an equivalent current) and achieves an impressive voltage efficiency of 70% at a current density of 100 mA cm−2. Notably, energy efficiency sees a notable uptick from 58% to 67% under the same current density conditions. These compelling outcomes underscore the immense potential of the carbonized waste cotton cloth electrode for widespread integration in VRFB installations at scale.

Synergetic Effects of Soil Organic Matter Components During Interactions with Minerals.

Mineral-associated soil organic matter (SOM) is critical for stabilizing organic carbon and mitigating climate change. However, mineral-SOM interactions at the molecular scale, particularly synergetic adsorption through organic-organic interaction on the mineral surface known as organic multilayering, remain poorly understood. This study investigates the impact of organic multilayering on mineral-SOM interactions, by integrating macroscale experiments and molecular-scale simulations that assess the individual and sequential adsorption of major SOM compounds-lauric acid (lipid), pentaglycine (amino acid), trehalose (carbohydrate), and lignin onto soil minerals. Ferrihydrite, Al-hydroxide, and calcite are exposed to SOM compounds to determine adsorption affinities and binding energies. Results show that lauric acid has 20-40 times higher Kd than pentaglycine, following the order Kd(ferrihydrite) > Kd(Al-hydroxide) ≫ Kd(calcite). Molecular-scale simulations confirm that lauric acid has a higher binding energy (30.8 kcal/mol) on ferrihydrite than pentaglycine (6.0 kcal/mol), attributed to lipid hydrophobicity. The lower binding energy of pentaglycine results from its hydrophilic amide groups, facilitating partitioning into water. Sequential experiments examine how the first layer of lipid or amino acid affects the adsorption of carbohydrate/lignin, which show little or no individual adsorption affinities. Macroscale results reveal that lipid and amino acid adsorption induce ferrihydrite particle repulsion increasing reactive surface area and enhancing carbohydrate/lignin adsorption independently and synergistically through organic multilayering. Molecular-scale results reveal that amino acid adsorbed on ferrihydrite interacts more readily with lignin macroaggregates (preformed in solution) than with individual lignin units, indicating organic multilayering via H-bonding. These findings reveal the molecular mechanisms of SOM-mineral interactions, crucial for enhancing soil carbon stabilization.

Assessment of reactive surface and kinetic parameters of basaltic rocks during CO2 storage

Carbon capture and storage (CCS) is a novel technology that aims to reduce the presence of carbon dioxide from the atmosphere. This technology involves capturing CO2 from industrial sources or directly from the air, treating, transporting, and storing it in long-term safe rock formations. Basaltic rock comprises reactive minerals and glassy phases, which trap CO2 permanently through the mineralization mechanism. However, this method is complex mainly due to the rapid interaction between solid and liquid phases. The mineralization occurs at the interface between the reactive fluid and the basaltic rock surface, converting the dissolved CO2 into solid carbonate mineral that precipitates in the pores and fractures of the rock matrix. The reaction rate of a basaltic rock depends significantly on the CO2 wettability and rock-fluid interfacial interactions. However, there is limited information about the influence of the reactive surface on the reaction rate of minerals present in basalt formations. This work investigates the influence of kinetics parameters such as pH, temperature, and reactive surface area in the reaction rate of basaltic rocks. Basaltic rock dissolution and precipitation is assessed using the geochemical software PHREEQC. The proposed numerical model solves the reactive transport problem and provides feedback on the influence of the kinetics reaction parameters. The dynamics of the reactive surface during the reaction of basalt rocks is evaluated. The numerical results show the potential of basaltic rock for CO2 mineral storage as solid carbonates and identify the main factors that limit the mineralization process. Finally, this work provides a deeper understanding of CO2 mineralization that can provide valuable findings to guide Brazilian CCS projects.

Promoting bioelectrochemical performance of microbial fuel cells by using the polyhedral single atom catalyst Cu doping on g-C3N4 and NiFeCo-layered double hydroxide (SAC Cu-g-C3N4@NiFeCo-LDH)

Single atom catalyst Cu doping on g-C3N4 and NiFeCo-layered double hydroxide (SAC Cu-g-C3N4@NiFeCo-LDH) was prepared by hydrothermal method, consisting of Cu-doped g-C3N4 polyhedral monoatom combined with NiFeCo-LDH, as a cathode catalyst for microbial fuel cell (MFC). A narrow diamond-shaped blocks with irregular edges was observed in SAC Cu-g-C3N4@NiFeCo-LDH, contributing to provide abundant active sites and surface area for reaction. The maximum power density of 242.521 mW/m2 and output voltage of 0.843 V were obtained by SAC Cu-g-C3N4@NiFeCo-LDH MFC. Moreover, the output voltage of SAC Cu-g-C3N4@NiFeCo-LDH MFC could be stabilized at around 0.518 V with minimal variation within 4 d. The above results illustrated that SAC Cu-g-C3N4@NiFeCo-LDH possessed the superior ability to enhance the bioelectrochemical performance of MFCs. This study would provide a theoretical basis for the novel catalyst on MFC reactors.

Energy Release Characteristics of Laser Ignited Al/PTFE Reactive Materials

Abstract In this study, the energy release mechanism in aluminum/polytetrafluoroethylene (Al/PTFE) reactive materials was investigated through combustion experiments employing laser ignition. Al/PTFE specimens with different Al particle sizes and different ratio were prepared by molding and sintering. The combustion processes and temperature fluctuations were documented using high-speed cameras and temperature sensors. It was found that specimens with micron Al failed to sustain combustion following the cessation of laser energy, whereas specimens with nano Al displayed a lower ignition threshold and sustained self-propagating reactions. The high surface reactivity and extensive specific surface area increased the susceptibility of specimens with nano Al to oxidation, which, following initial reactions, resulted in diminished reactivity and reduced energy release compared to specimens with micron Al. As the Al content increases in the specimens, the time required to reach the highest reaction temperature is reduced, concurrently with an augmentation in energy liberated. This correlation substantiates that within specified boundaries, an elevation in Al content precipitates an enhancement in both the efficacy and magnitude of the energy release.

Evaluation of CO2 Leakage Potential through Fault Instability in CO2 Geological Sequestration by Coupled THMC Modelling

A faulted saline aquifer system was simulated in a coupled thermal-hydraulic-mechanical-chemical (THMC) framework to examine the potential breaching of the caprock seal from long-term CO2 sequestration. The pH of the brines steadily dropped from 7.5 to 4.7 due to the continuous injection of scCO2 (supercritical CO2), which was caused by the rapid dissolution of calcite in the reservoir and associated fault zones, alongside alterations in the concentrations of primary and secondary minerals within the formation. The increase in pore pressure with the continuous injection of scCO2 triggered fault reactivation at 6y with the resultant leakage of CO2 along the fault. This builds CO2 saturation inside the fault at 7y to six-fold higher than pre-slip. Continuing shear reactivation and creation of reactive surface area following the initial CO2 leakage accelerates dissolution/precipitation reactions, in turn further increasing porosity and permeability of the reservoir and fault. In particular, the permeability and porosity in the fault zone were increased by only 2% and 6%, respectively – staunched by competitive feedbacks in dissolution countered by precipitation that are individually much larger. Comparison of mineral concentrations adjacent to the fault before-and-after instability revealed that the development of shear failure also promotes the transport of reactivated minerals into the fault zone. Among them, feldspar changes most significantly in later stages, dominated by dissolution with the volume fraction decreasing by 80% and increasing the aqueous concentration of K+ by approximately an order of magnitude. However, secondary minerals counter this dissolution through precipitation with the volume fraction of kaolinite increasing by an order of magnitude compared with the original fraction. Finally, the evolution of the fault sealing coefficient (FS) demonstrates that the porosity and permeability exert a pivotal influence in controlling the self-sealing behavior in the basal of the fault, while the upper fault layer exhibits self-enhancing response. A notable observation is that changes in mineral ion concentrations in fault zones could be applied as a significant diagnostic signal to monitor fault stability and the potential for progress of self-sealing behavior.

Electrospun polyvinyl alcohol/chitosan nanofibers modified with carbon nanotubes and sliver particles for electrochemical sensor application

Polyvinyl alcohol (PVA)/chitosan (CS) nanofibers modified with carbon nanotubes (CNT) and silver (Ag) particles are electrospun onto a graphite plate (GP) substrate to form the PVA-CS-CNT-Ag/GP electrode for electrochemical sensor application. Microstructure characterization demonstrates that PVA-CS nanofibers exhibit a loose and porous network structure, significantly improving the effective reaction surface area. Electrochemical measurements show the PVA-CS-CNT-Ag/GP electrode exhibits the limit of detection of 23.2 μM, the linear range of 65–176,460 μM and the sensitivity of 3.3945 μA cm−2 mM−1. Anti-interference test results show that the sensor has high selectivity towards H2O2. Stability test results indicate that the sensor exhibits good stability, as evidenced by the response current of 83.94 % after a period of 30 days. Simulation calculations indicate that PVA-CS-CNT-Ag exhibits lower interfacial energy (−2.3293 eV) compared to PVA-CS-CNT (−0.3674 eV) and PVA-CS-Ag (−0.7646 eV), smaller band gap (0.318 eV) compared to PVA-CS (3.640 eV), higher density of states at Fermi level (14.7332 electrons/eV) than others. Experimental measurements and simulation calculations indicate that PVA-CS-CNT-Ag electrospun nanofibers exhibit promising potential as an electroactive material for the electrochemical detection of H2O2.

Influence of Catalyst-Layer Defects on PEMFC Degradation

Improving the durability of polymer electrolyte membrane fuel cells (PEMFCs) is essential for expanding their applications. Defects in the catalyst layers of PEMFCs may occur during their manufacturing or operation; however, the influence of these defects on PEMFC degradation has not yet been clarified. Carbon corrosion is a major factor affecting PEMFC degradation. It leads to the detachment of Pt, resulting in a reduction in the reaction surface area. Our study focused on the influence of the defects in the catalyst layer on carbon corrosion and performance degradation. Previous studies have reported that carbon corrosion progresses mainly under the conditions of either proton deficiency or potential fluctuations [1, 2].Figure 1 shows two types of membrane electrode assemblies (MEAs) with the electrode areas of 1 cm2. One had no defects, whereas the other had a defect with a diameter of 6 mm at the center of the anode catalyst layer. The CO2 concentration in the cathode outlet gas was measured under several rectangular potential fluctuations to evaluate the amount of carbon corrosion. Figure 2 shows that the amount of carbon corrosion increased as the upper potential increased or the lower potential decreased in both the MEAs with and without defects. The MEA with a defect exhibited a higher amount of carbon corrosion than the MEA without defects at all potential fluctuations. The rate of increase varied for each potential fluctuation and ranged from 9% to 26%. In this study, the influence of several types of defects in the catalyst layers on the performance degradation is discussed using the amount of carbon corrosion.

The Development of Uniform-Sized Pt-Based Binary Alloy Electrocatalysts for ORR in Polymer Electrolyte Fuel Cells

For the large-scale commercialization of fuel cell vehicles (FCVs) in Japan after 2030, NEDO is aiming to reach a target cell performance of 0.84 V at 0.2 A cm－ 2 for polymer electrolyte fuel cells (PEFCs).1 It is desirable to achieve the target performance using a catalyst with a reduced amount of platinum (Pt) and high durability. Alloy-core and Pt-skin structured Pt-based alloy catalysts offer many benefits for reducing the platinum amount and raising the durability. 2-4 Therefore, this study presents the structural characteristics and electrocatalytic activities of the alloy-core and Pt-skin PtM/C (M = Co, Ni, and Fe) binary alloy catalysts with uniform particle sizes and large electrochemical surface areas for the cathodic oxygen reduction reaction (ORR) in PEFCs.The PtM/C (Pt: 35 wt.%, M= Fe, Ni, and Co) alloy catalysts supported on a commercial carbon (KB-600JD, SBET: 1335 m2 g－ 1) were prepared by an impregnation method. Briefly, Pt(NO2)2(NH3)2 and transition metal precursor (Mx(NO3)y) solutions were first impregnated into the carbon suspension. Subsequently, a dry powder was annealed at 880 ºC for 1 h under 5% H2/Ar atmosphere. Finally, the alloy catalyst was leached by 1 M HNO3 at 80 ºC for 12 h, followed by the treatment at 500 ºC in 5% H2/Ar atmosphere. The structure and composition were analyzed using TEM, XRF, TGA, and XRD. The electrocatalytic activity was evaluated by the RDE method. CV and LSV curves were recorded in N2- and O2-saturated electrolyte (0.1 M HClO4), respectively. The CO stripping experiments were carried out by absorbing CO gas at 0.05 V. A single-cell test was performed on MEA (1cm2). The MEA was fabricated by sandwiching a membrane electrolyte (NRE211) with the anode and cathode containing the catalyst layers (Pt loading: 0.17 mg cm－ 2 and I/C: 1) on the carbon papers (MB30). The I-V measurement was conducted on the cell at 80 ºC supplied by H2 (418 nccm, 75% RH) and air (998 nccm, 75% RH) under a backpressure of 50 kPaG. The catalyst durability was evaluated by applying square wave cycling according to a revised protocol of NEDO.5 TEM images reveal a uniform dispersion and a narrow particle size distribution of PtM/C alloy nanoparticles. The average particle sizes of PtFe/C, PtNi/C, and PtCo/C (~400 particles) were 2.95, 3.22, and 2.94 nm, respectively, indicating the formation of relatively small-sized nanoparticles. As shown in Figure 1, PtNi/C and PtCo/C catalysts have a disordered fcc-structure (SG: Fm3̅m, PDF#03-065-9445, PDF#01-072-9178). The PtFe/C catalyst exists in an ordered fct-phase (SG: P4mmm, PDF#01-073-2622). Metal ratios in the alloy nanoparticles of PtFe/C (2.9:1), PtNi/C (3.7:1), and PtCo/C (3.8:1) were calculated by Vegard’s law from a Pt (111) plane. The ECSAHUPD values for PtFe/C, PtNi/C, and PtCo/C catalysts were lower (89.7 m2 g Pt － 1, 75.7 m2 g Pt － 1, and 71.1 m2 g Pt － 1) than ECSA COads. values (102 m2 g Pt － 1, 96 m2 g Pt － 1, and 93 m2 g Pt － 1). The mass activity (MA) of ORR shows an increasing order of 0.94 A mg－ 1 Pt (PtNi/C) > 0.97 A mg－ 1 Pt (PtCo/C) > 1.42 A mg－ 1 Pt (PtFe/C) and surpasses that of commercial PtCo/C (0.62 A mg－ 1 Pt). Figure 2 shows the I-V (H2-Air) polarization curves of PtM/C and commercial PtCo/C catalysts measured at 80 ºC of cell temperature under 50 kPaG. The PtM/C catalysts show higher cell performances at low current density (0.2 A cm－ 2) such as 0.770 V (PtFe/C), 0.772 V (PtNi/C), and 0.772 V (PtCo/C), compared with the value (0.762 V) of the commercial PtCo/C catalyst. In addition, the ECSAs for all PtM/C catalysts were maintained after 10000 cycles in ADT (RDE), indicating that the ionomer could transfer from the catalyst surface into the carbon pores, thereby increasing the number of active sites.7 The MA of PtM/C catalysts has surpassed that of the commercial PtCo/C catalyst, showing their improved durability. These findings suggest that the PtM/C catalysts with the low Pt amount could still be promising candidates for ORR in PEFCs.This study was partly supported by NEDO, Japan.References NEDO roadmap, https://www.nedo.go.jp/content/100973008.pdf (in Japanese)Liu et al., J. Am. Chem. Soc., 146, 2033 (2024).Zhao et al., ACS Catal., 10, 10637 (2020).T. Y. Yoo et al., Energy Environ. Sci., 16, 1146 (2023).NEDO, PEFC evaluation protocol, https://www.nedo.go.jp/content/100963953.pdf (in Japanese)Catalyst activity evaluation protocol of FC-Cubic (in Japanese).Kobayashi et al., ACS Appl. Energy Mater., 4, 2307 (2021). Figure 1

Inverse Design of Porous Electrodes in Redox Flow Batteries: A Computational Approach Integrating Topology Optimization and Multi-Physics Modeling

The increasing effects of global climate change urge a global energy transition, in which large-scale storage of renewable energy technologies is expected to play a primary role. Redox flow batteries (RFBs) have emerged as a promising technology for grid-scale energy storage with appealing features such as higher durability and power-energy decoupling. During the RFB operation, the liquid electrolytes, stored in external tanks, are actively circulated through the electrochemical stack consisting of flow fields, porous electrodes, and membranes, where electrochemical reactions take place on the surface of the porous electrodes, which are performance-defining components [1]. Despite its advantages, RFB technology has seen limited adoption due to economic and technical challenges. Aiming to boost cost-effectiveness, one effective strategy is to increase the stack power density by increasing the efficiency of the electrodes leading to an increase in the overall system performance [2]. Optimizing reactor performance is challenging due to seemingly contradictory requirements such as providing high surface area for reactions, reducing ohmic drop across the cell, facilitating mass transport in porous media, and reducing pumping power requirements.Parallel to experimental research, computational techniques have the potential to accelerate and guide the design of porous electrodes. An emerging approach in this regard is to use predictive design algorithms that invert the design process and enable the exploration of a broader design space. Topology optimization (TO) is a powerful inverse design technique combining numerical simulations with mathematical optimization algorithms, which involves setting a performance target of minimizing the pumping power and overpotential losses and iterating mathematically over various electrode structures to satisfy the target [3, 4]. This approach requires integrating two different types of models: 1) multi-physics models to build a theoretical framework to adequately relate the local electrode properties to the overall RFB performance, and 2) TO models to inversely design microarchitected variable porosity 3D porous electrodes.In this research, we have developed a high-performance TO framework for three-dimensional porous electrodes in next-generation RFBs integrated with multi-physics computational models of mass, momentum, and charge transport processes using the porous electrode theory, in which the electrode was considered as a macroscopic porosity-variable block. The model was developed using finite element/volume methods implemented using the open-source codes Firedrake, OpenFOAM, and PETSc. The macroscale TO problem was formulated to maximize electrochemical performance under a controllable pumping power loss in a half-cell redox flow cell. The resulting designs were transformed into cellular architectures using triply periodic minimal surface (TPMS) structures and additively manufactured using stereolithography 3D printing followed by carbonization, the output of which can be used to assess the performance of the inversely designed electrodes in a real setup.In this presentation, I will first discuss the structure of the multi-physics modeling approach. Second, I will present the integration of these models into the TO algorithms. Finally, I will show the transformation of the TO results into cellular infills and will highlight some technical aspects of the manufactured TPMS structures.

Exploring Iron-Containing Electrodes for Use as Negative Electrodes of All-Iron Redox Flow Batteries

The transition towards a renewables-based energy economy is motivated by pressing environmental concerns and economic growth rates. This new energy paradigm necessitates efficient, robust and cost-effective, large-scale energy storage systems. Aqueous, all-iron redox flow batteries (AIRFBs) are a promising contender for large-scale energy storage, motivated by their reliance on environmentally friendly and abundant raw materials, their intrinsic safety, and projected high energy density (ca. 135 Ah L-1) [1]. However, the performance and lifetime of state-of-the-art AIRFBs are greatly limited the poor kinetics and uneven plating taking place in the negative half-cell. Traditionally, the electrochemical stack leverages carbon fiber-based electrodes (e.g. felts), which provide moderate surface area for reaction but suffer from sluggish kinetics and plated layers of poor quality [2].Hereby, we explore the use of iron-based (e.g. pure iron, steel types 302, 316, 420) electrode alternatives to overcome the challenges of prevalent carbon fiber electrodes or pure iron. Steels have been investigated for numerous electrochemical systems, such as (microbial) fuel cells, electrolyzers and various types of batteries, displaying high performance and excellent chemical stability, robust mechanical properties and low production costs [3]. More precisely, in this work we investigate iron-based electrodes as a substitute for conventional carbon felts due to their enhanced kinetic activity in the negative half cell [Fe2+(aq)|Fe(s)]. Firstly, different metal electrodes were tested in flow-by configuration to obtain their polarization performance. Employing a flat electrode of pure alpha-iron as a baseline, we find that it displays balanced behavior between charging and discharging mode, although it exhibits very limited utilization of its projected gravimetric capacity[4]. Following this, we test a set of steel sheets of different nature, that is, ferritic, martensitic and austenitic, which contain various alloying elements (e.g., Cr, Ni, Mn, Mo, etc.) in different ratios, resulting in different electrochemical performance. We find that materials containing low to moderate Ni:Cr ratios result in enhanced iron plating and stripping kinetics, with increases ranging from ~20 to ~60% with respect to the pure alpha-iron electrode. Furthermore, we observe that the crystallographic structure of austenitic materials tend to favor reactions involving iron ions, as opposed to martensitic structures of which feature higher solid-to-gas surface energy, which favor the competing hydrogen evolution reaction [5]. We additionally investigate advanced three-dimensional structures in a symmetric, flow-through configuration, by selecting the best performing steel composition. By screening various fiber arrangements, we aim to elucidate the structural effects on mass transfer and overall cell performance.Overall, we studied the interplay between the composition and architecture of different metal-based electrodes. We hope that these findings will help shed light on their potential to improve the performance of the challenging iron plating-stripping reaction and ultimately introduce them in a full cell system to enable higher capacity and rate performance of the promising all-iron flow battery Acknowledgments IGG gratefully acknowledges financial support by “la Caixa Foundation” (ID 100010434) under the fellowship number LCF/BQ/EU20/11810076. AFC gratefully acknowledges funding by the European Union (ERC, FAIR-RFB, ERC-2021-STG 101042844). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.

Flashlight-Induced Ultrafast, Scalable Surface Activation of Highly-Loaded Graphite Composite Anode

Numerous substantial challenges persist in achieving widespread and pragmatic applications of LIBs, including further improvements in energy and power density, safety, and cost reduction. One of the many efforts to address them is to increase the loading level of electrodes. This can not only improve energy density per unit area, but also dramatically lower the cost of the battery pack by reducing the stacking number of cells and the use of inactive components such as current collectors and separators. However, contrary to the expectation of such a positive effect, it had been shown that increasing the loading level, i.e., the thickness of the electrodes often resulted in a degradation of the electrochemical properties of the cell. For a thick electrode, a large amount of solvent is volatilized when drying, causing more binder to migrate to the electrode surface, and the paths that the lithium ions and electrons travel become longer and more tortuous. These lead to inhibition of lithium ion diffusion and the accumulation of a solid electrolyte interface (SEI) layer and dead lithium at the interface between the electrode/electrolyte, and consequent degradation of cell performance such as rate capability.Several emerging materials with enhanced electronic and ionic conductivity are being developed to overcome the performance degradation arising from thickened electrode, but their practical use is hampered by the long time required to verify mass production and performance reliability. Another approach is to build thick electrodes into a three-dimensional (3D) porous structure that is effective for ion and electron transfer. Specially, anisotropic structure with vertical microchannels serving as the high transport pathway had known to enhance the electrolyte permeability into the electrode and alleviate the resistance to ion migration at the electrolyte-electrode interface. This promoted lithium ion diffusion within thick electrode, allowing enhanced rate capability and high volumetric capacity. resulting in improvement of rate capability, and magnetic templating or laser ablation are commonly used to create them. However, for these technologies to be implemented in the battery manufacturing industry, there are still issues that need to be solved, such as a complex and time-consuming manufacturing process, incompatibility with roll-to-roll process and significant loss of active material due to structuring. Therefore, it is important to develop more effective strategy to overcome the limitations in thick electrodes.From this perspective, in this study, we explored a new and efficient way to address the challenges posed by highly-loaded graphite composite anode using a flash annealing process that is roll-to-roll compatible and capable of large-area processing. When a flashlight is irradiated on the surface of a high-energy-density electrode for less than a second, the light energy absorbed by the graphite active material and conductive carbon additives can be converted to thermal energy. At this time, the surrounding binder can undergo an instantaneous carbonization reaction by the heat, which eventually can form into a porous carbon nanostructure. In addition, some of the weakly bound active material can be cleaned away from the surface, creating pores and bumps on the electrode surface. These changes of electrode surface derived from the interaction with the flashlight can contribute to easier penetration of the electrolyte, increased reaction surface area and improved conductivity, which can lower the transfer resistance of electrons and lithium ions in a thick anode. To confirm these effects, the structural and chemical changes on the electrode surface after irradiation with flashes of different energies were closely analyzed, and the improvement in electrochemical properties such as performance stability and rate capability was confirmed by implementing flash-treated highly loaded graphite anode over 3.6 mAh/cm² into half-cell. Functionalization of the electrode surface using flashlight is not only effective in improving the electrochemical performance degradation caused by the adoption of thick electrodes, but also has the advantage of being compatible with the roll-to-roll process which is mainly adopted by the battery manufacturing industry, as it can be performed in milliseconds on a large area. Therefore, it is expected to become a new growth engine for the battery manufacturing industry in the near future.

Catalytic gasification of a single coal char particle: An experimental and simulation study

The catalytic coal gasification technology has been widely researched and developed under the background of “Carbon peaking and carbon neutrality goals”. Currently, most of catalytic gasification experiments on coal char particles are analyzed by thermogravimetric analyzer (TGA). However, the gasification agent will be subject to diffusion resistance during the reaction because of the sample stacking, making the inherent reaction kinetics unclear. In this study, we investigated the catalytic gasification behavior of single-particle coal char using high temperature stage microscope (HTSM). With the diffusion resistance ruled out, the reaction conditions when using a HTSM are more similar to those inside a real industrial gasifier. Numerical models of the gasification reaction of single-particle coal char were further developed using the kinetic parameters obtained under HTSM. Three models were investigated, including regular spherical structured, irregular spherical structured and porous spherical structured models, representing different morphologies of coal char particles in the gasifier. The gasification characteristics of coal char particles under different K2CO3 catalyst loadings and gasification temperatures were also studied. Compared with the activation energies data of coal char particles without catalyst, the activation energies of coal char particles loaded with 2.2 %, 4.4 %, 6.6 %, and 10.0 % catalysts were reduced by 110 kJ/mol, 116 kJ/mol, 121 kJ/mol, and 126 kJ/mol, respectively. The reaction surface area affects the temperature distribution. The temperature near the irregular spherical particle is about 20 K higher than the temperature near the regular spherical particle.

Insight into discharge of non-aqueous Li–O[formula omitted] battery using a three-dimensional electrochemical lattice Boltzmann model

Non-aqueous Li–O2 battery (NALiO2B) is a promising alternative to lithium-ion batteries, offering high theoretical energy density. However, its practical applications are hampered by limited understanding of the underlying mechanisms. In this study, a three-dimensional electrochemical lattice Boltzmann method is proposed to simulate the physical and electrochemical processes during NALiO2B discharge at the pore scale. The discharge performance of NALiO2B is evaluated for various electrode and electrolyte designs. It is found that the limited O2 diffusion within homogeneous electrodes is the primary cause of the declined reactive electrode surface area, the intensified electrochemical reaction (or overpotential), and finally the premature battery death. This issue can be mitigated by employing the hierarchical electrode BP2 with a bi-porous structure. The large pores in BP2 improve O2 transport to sustain the continuous electrochemical reaction process, thus enhancing the discharge capacity of NALiO2B. To further boost the rate capability of NALiO2B, BP2 is partially infiltrated with electrolyte to form the multiphase (MP) electrode, where air bubbles exist and serve as O2 reservoirs. These bubbles effectively provide adequate O2 to support the extensive O2 consumption during the fast electrochemical reaction at high current densities. Consequently, NALiO2B with MP demonstrates the satisfactory discharge capacity and rate capability. This study provides valuable insights into the complex physics and reaction kinetics behind NALiO2B discharge, which facilitates the optimization and development of NALiO2B.

Hydrothermal Formulation of Dy2MoO6@rGO Nanostructure for Supercapacitors

The exceptional intrinsic conductivity and structural stability of mixed transition metal oxides (MTMOs) make them a significant pseudocapacitive electrode for supercapacitors. However, a major challenge is their inappropriate structures facilitating extended cycling life and rapid Faradic redox reactions. The present research reports the hydrothermal combination of dysprosium molybdate (Dy2MoO6) with reduced graphene oxide (rGO) to advance the specific capacitance (Cs) and rate performance of supercapacitors. While comparing pure Dy2MoO6, the Dy2MoO6@rGO nanocomposite exhibits a higher Cs of 1118 F g−1 at a current density (j) of 1 A g−1 and retention capacitance of 83.7 % after 10,000 successive cycles. The enhanced electrochemical performance of Dy2MoO6@rGO results from its advantageous features, such as high structural stability, greater reactive surface area, favorable ion adoption, and rapid ion/electron transfer rate during the redox phenomenon. Furthermore, the asymmetric supercapacitors (ASCs) employing Dy2MoO6@rGO as the positive and activated carbon (AC) as the negative electrodes presented a Cs of 282 F g−1 at a rate of 1 A g−1. When operated at 1.6 V, the constructed Dy2MoO6@rGO//AC ASC achieves an outstanding energy density (Ed) of 19.2 Wh kg−1 and a power density (Pd) of 272.2 W kg−1. These outstanding findings suggest that the created nanostructures Dy2MoO6@rGO can be used in ultra-performance ASC devices. Moreover, the method simplifies developing efficient energy storage devices using MTMOs by enhancing capacitance and expanding the potential range in an alkaline electrolyte.

Nanomolar level detection of phosphodiesterase 5 inhibitor drug tadalafil based on halide perovskite@HNTs nanocomposite electrode

As halide perovskites have taken a central role in the evolution of semiconductor materials, they are setting new standards for performance and revolutionizing the energy sectors. Unfortunately, little light is shed on the material's electrochemical sensing capabilities. This work reports the synthesis and characterization of a novel double halide perovskite Cs2CaSnCl6 (HDP) integrated with halloysite nanotubes (HNTs) for the electrochemical detection of Tadalafil (TAD). HDP@HNTs nanocomposite is synthesized using a simple solvothermal method and is characterized using various techniques like SEM, TEM, UV–visible, FT-IR, TGA/DTA, XRD and BET analysis. The results obtained from these characterizations confirmed the successful formation of the nanocomposite, revealed the material's endurance to high temperatures and the availability of a large surface area for reaction. Electrochemical characterization techniques like cyclic voltammetry (CV) and linear sweep voltammetry (LSV) demonstrated a linear correlation with the concentrations of TAD. Computational analysis of the TAD structure optimization, molecular electrostatic potential (MEP) of TAD and calculations regarding the HOMO-LUMO molecular orbitals are all carried out using the DFT/B3LYP method. The HDP@HNTs sensor is capable of achieving the lowest detection limit of 1.68 nM and the limit of quantification of 5.09 nM. The material showcased a remarkable sensitivity of 0.0104 µA nM-1 cm-2 from all the electrochemical parameters. Its reliability and stable performance even in the presence of real samples makes it a promising material for sensing applications. Thus, the reported framework contributes to the advancement in the development of sensors and enhanced healthcare outcomes.