Bimodal Pore Research Articles

Engineering Electrodes with Bimodal Pore Size Distributions for Next-Generation Electrochemical Devices

In many electrochemical conversion devices such as low temperature fuel cells or water electrolyzers, the transport of reactants to and products from the catalyst layer is facilitated by porous structures referred to as gas diffusion layers or porous transport layers. They bridge the gap between flow fields and catalyst layers and their mass transport capabilities become especially critical at high current density operation. Excessive accumulations of reaction products or a lack of fresh reagents stall out the electrochemical conversion resulting in reduced efficiencies or even damage to the system itself due to fuel starvation1. Thus, to realize cost-competitive electrochemical systems we must overcome the fundamental challenge of multiphase flows in which liquid and gaseous phases flow through porous structures in opposing directions.In recent years, porous electrodes have been adapted to better address these issues and improve performance. For example, the addition of a layer with reduced pore size facing the catalyst layer (i.e., micro porous layer) was shown to increase performance in fuel cells and electrolyzers2–4. Furthermore, chemical5 as well as mechanical6,7 methods of creating dedicated liquid and gas pathways in the structure have been investigated with promising results. These approaches are however intrinsically limited by the microstructure of the material they are applied to.Inspired by the success of these modifications, we propose a novel structure containing both a pore size gradient as well as dedicated water and gas pathways in the form of bimodal pore size distributions (Figure 1). This material is generated by depositing a metal in the presence of gas evolution to form a structure containing microscopic and macroscopic pores. This type of material has in the past been used successfully to improve boiling heat transfer8, another process faced with the counterflow of liquid and gas. They have also been investigated as high surface area material for microbial anodes9 and have been postulated to find application in other electrochemical devices such as batteries or fuel cells10. In this talk, I will discuss the synthetic approach to manufacture self-standing porous electrodes using an electrochemical flow platform and elucidate the correlation between applied electrochemical parameters and resulting material microstructure. Properties such as electrode thickness and pore sizes can be adjusted during the synthetic process to suit the requirements of specific applications exhibiting complex mass transport requirements.Acknowledgements:This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 899987.

Towards Bottom-up Design of Porous Electrode Microstructures – an Approach Coupling Evolutionary Algorithms and Pore Network Modeling

Porous electrodes are performance- and cost-defining components in modern electrochemical systems such as redox flow batteries, fuel cells, and electrolyzers. They must facilitate mass transport, provide surfaces for electrochemical reactions, and conduct electrons and heat. Thus, understanding and optimizing the porous electrode microstructure offers a promising pathway to cost reduction by increasing power density (1). However, our current arsenal of materials is limited to fibrous carbonaceous electrodes that were developed for low temperature fuel cells and are now repurposed to emerging systems (i.e., redox flow batteries), which fundamentally limits the performance. The empirical design of electrodes is time- and resource-intensive which limits exploration of the wider design space. To accelerate progress, microstructure-informed multiphysics simulations can be leveraged to aid the theoretical understanding and design of advanced electrode architectures but has primarily focused to the investigation of existing, carbon-fiber-based electrodes (2–4). In this work, we explore the following scientific question: Can we deploy three-dimensional simulations in combination with evolutionary algorithms to enable bottom-up artificial generation of porous electrodes? In the first part of this talk, I will discuss the modeling framework and experimental validation. Using a pore network modeling open-access platform (OpenPNM) (4, 5), we built a microstructure-informed, electrolyte-agnostic simulation framework. In this work, we focus on redox flow batteries as an application case. The model utilizes a network-in-series approach to account for species depletion over the entire length of the electrode, thus enabling the simulation of large electrode sizes (17 mm x 1 mm x 210-400 μm). To validate the robustness of the modeling framework, we performed symmetric flow cell experiments for two distinct electrolytes - an aqueous Fe2+/Fe3+ and a non-aqueous TEMPO./TEMPO+ - and two types of porous electrodes – a Freudenberg carbon paper and an ELAT carbon cloth - (Figure 1a). The dry electrode microstructures were obtained with x-ray computed tomography and converted into a network of spherical pores and cylindrical throats using the SNOW algorithm (6). The electrochemical model is solved for the electrolyte fluid transport and couples both half-cells by iteratively solving the species and charge transport with low computational cost (-1 – 0 V, with -0.05 V step intervals takes 60-120 min on an Intel® Core(TM) i7-8750H CPU). The electrochemical performance of the non-aqueous electrolyte was well captured by the model without fitting parameters, allowing rapid benchmarking of porous electrode microstructures. For the aqueous electrolyte, we find that incomplete wetting of the electrode results in overprediction of the electrochemical performance. To account for incomplete wetting, we successfully employ a fitting parameter to account for the near-surface mass transfer coefficient (7).In the second part of the talk, I will describe a genetic algorithm that optimizes porous electrode microstructures from the bottom-up by coupling the pore network modeling framework with an evolutionary algorithm. Our goal is to optimize electrode microstructures by only having the electrolyte chemistry and flow field geometry as inputs. The microstructure evolves driven by a fitness function that minimizes pumping power requirements and maximizes electrochemical power output. The analyzed systems show significant improvement of the networks’ fitness, which increased by 30-400%. For flow-through flow fields, the pumping requirements are dominant and were reduced by 60-70%, resulting in a bimodal pore size distribution with large-pore longitudinal electrolyte flow pathways (Figure 1b). Additionally, the surface area at the membrane-electrode interface is increased for all systems, resulting in an increased electrochemical performance of 3-8%. The presented framework offers great potential for predictive design of electrode microstructures tailored for specific redox chemistries and reactor architectures, which will accelerate and broaden the design and fabrication process of advanced electrode structures. While applied to flow batteries here, this methodology can be leveraged to advance other electrochemical systems by adapting the relevant physics. References A. Forner-Cuenca, F. R. Brushett, Curr. Opin. Electrochem., 10 (2019).G. Qiu et al., Electrochim. Acta. 64, 46–64 (2012).A. G. Lombardo, et al., J. Energy Storage. 24 (2019).M. A. Sadeghi et al., J. Electrochem. Soc. 166, A2121–A2130 (2019).J. Gostick et al., Comput. Sci. Eng. 18, 60–74 (2016).J. T. Gostick, Phys. Rev. E. 96, 1–15 (2017).K. V. Greco, et al., ACS Appl. Mater. Interfaces. 10, 44430–44442 (2018). Figure 1

Wetting-drying cycle effect on the compressibility of lime-treated soil accounting for wetting fluid nature and aggregate size

The durability, which refers to the ability of earthen structures to ensure their functionality over time while maintaining their required mechanical performance, is a key issue in evaluating the effectiveness of lime treatment. In this study, the effect of wetting-drying cycles on the compressibility and the microstructure was investigated with lime-treated/untreated samples considering the wetting fluid and the maximum aggregate size (S0.4, Dmax = 0.4 mm; S5, Dmax = 5 mm) effects. Results showed that the wetting-drying cycles caused an increase of void ratio and changed the bi-modal porosity to tri-modal characteristics for the untreated samples, while it led to a reversible variation of void ratio and an unchanged bi-modal pore size distribution characteristics for lime-treated samples, indicating the soil improvement by lime treatment. Thereby, the wetting-drying cycles made the compression curve of untreated samples change from convex to linear shape, while their effect was visible but not significant for the lime-treated soil. Higher decrease of macro-pore void ratio with loading was obtained on the lime-treated samples under wetting-drying cycles compared to the as-compacted samples, indicating a slight softening of soil structure by the wetting-drying cycles. Regarding the effect of wetting fluid nature, synthetic seawater resulted in a higher compressibility than deionised water. This was attributed to the presence of higher quantity of macro-pores in the samples wetted by synthetic seawater induced by the shrinkage of clay fraction. The aggregate size had slight effect on the compressibility of as-compacted samples due to their similar production of cementitious compounds and matric suction. Nevertheless, after wetting-drying cycles, the lime-treated samples S5 had lower decrease of macro-pore void ratio than the lime-treated samples S0.4, due to the significant reduction of macro-pore population with wetting-drying cycles.

Biogas upgrading to syngas by combined reforming using Ni/CeO2–Al2O3 with bimodal pore structure

Ni/CeO2–Al2O3 with bimodal porous structure and two different CeO2 concentrations (low: 5 wt% and high: 15 wt%) were prepared by the refluxed co-precipitation method and characterized by N2 physisorption, XRD, TPR, H2-TPD, and CO2-TPD. Catalysts were tested in combined steam and dry reforming of methane (CSDRM) at atmospheric pressure, 600°C–700 °C and CH4: CO2: H2O = 1: 0.48: 0.8, in order to prepare synthesis gas with H2:CO ratio of 2:1. The catalytic activity decreases with increasing ceria content, the best catalyst being Ni/CeO2(5 wt%)-Al2O3. The good activity obtained for Ni/CeO2(5 wt%)-Al2O3 is a consequence of the more intimate contact of ceria with alumina, providing higher metal-support interaction, but also of the higher dimensions of larger pores which contribute to the better targeting of the reagents to the catalytic sites. In the used catalysts, the ceria presence better preserved the bimodal porous structure and decreased the carbon deposition by ∼70%.

Effect of porosity and phase composition in 3D printed calcium phosphate scaffolds on bone tissue regeneration in vivo

Highly porous calcium phosphate (CaP) scaffolds with multiple phases were fabricated through combination of material extrusion type 3D printing process, salt-leaching, and bone cement chemistry under physiological conditions. Scaffolds with nano-sized calcium deficient hydroxy apatite (CDHA) in the core and large crystals of dicalcium phosphate dihydrate (DCPD or brushite) on the outer surface were fabricated by immersing the 3D ceramic scaffold in aqueous ‘cement solution’. In contrast to conventional CaP cement reactions where a single product is obtained, here we could achieve a composite of apatite-brushite. The composite scaffolds showed improved compressive strength without loss of porosity which was suitable for efficient bone tissue regeneration. With 65 % porosity, these scaffolds showed compressive strength of 15 MPa. The porosity of CaP scaffold was increased by applying salt-leaching technique to 3D printing, which greatly influenced the biodegradation of the scaffold in vivo. Composite scaffolds with fast degrading brushite shell showed better and faster scaffold-to-bone integration compared to apatite based scaffold. In vivo studies verified that multi-phase CaP scaffolds with bimodal pore structure induced good new bone formation behavior (85 % of coverage rate on calvaria defect site after 11 weeks of implantation) with good biodegradability (76.6 % of degradation in rabbit subdermal model after 12 weeks of implantation).

Pore-scale network modeling approach to study the impact of Microporosity's pore space topology

Carbonates present a significantly important area for the research as classical empirical methods applied for sandstones characterization, may easily mislead when applied to carbonates. The impact becomes more protuberant when considering low resistivity pay carbonate formations where Archie's equation may yield higher than actual water saturation values, which, however, underestimate the hydrocarbon reserves. Especially, the bimodal pore sizes distribution makes carbonates extremely complicated for characterization through traditional digital rock physics applications. Unlike sandstone, for a given carbonate sample, it is almost impossible to have pore digital 3D images with minimum elementary volume (REV) to generate a standard pore-network model (PNM) due to the resolution and computational processing power limitations.

Evolution process of the microstructure of saline soil with different compaction degrees during freeze-thaw cycles

For backfill projects in seasonally frozen regions, freeze-thaw and compaction are two critical factors that affect engineering safety by changing the soil structure. This study investigated the effects of freeze-thaw cycles on the microstructure characteristics of saline soil with different compaction degrees using mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and laser particle size analysis (LPSA). The compacted soil samples show a bimodal pore size distribution (PSD). With an increase in the freeze-thaw cycles, the volume of intra-aggregate pores (<4 μm) gradually decreases, while that of inter-aggregate pores (>4 μm) varies with the density of soil samples. Furthermore, compaction has a decisive effect on the volume of inter-aggregate pores. Under the effect of freeze-thaw cycles, the void ratio of the low-density soil sample decreases, and the soil structure gradually becomes denser, showing thaw settlement deformation. However, in the high-density soil sample, the void ratio increases and the soil structure becomes loose, showing frost heaving deformation. Moreover, the freeze-thaw cycle also leads to the breakage of coarse particles and the aggregation of fine particles. Correspondingly, the soil structure type changes from a flocculent structure to a granular stacked structure and then to a cemented-aggregated structure. After 60 freeze-thaw cycles, the cracks are penetrated and the water migration channels are formed, the soil structures all reach a new equilibrium state. Meanwhile, the void ratios of different compacted soil samples are close to the same residual value. Test results suggest that there may be an optimal compaction degree between 90% and 95%, where the soil microstructure is least affected by freeze-thaw cycles. This study may provide theoretical guidance for the construction of backfill engineering projects in seasonally frozen regions from a micro-perspective.

Soilphysics: A suite of tools to fit and compare water retention curves

AbstractWater content plays a central role in soil physical dynamic processes. The relationship between water content and matric potential is key to understand many of these processes. However, there is not one but at least half a dozen parametric models that can properly describe that relationship, which might have different levels of complexity, varying from soil to soil. Thus, fitting some of those models is not always a trivial task. Moreover, few computational resources are currently available to do this; or else, they can be of complex use as the models get more complex. Here, we present a suite of functionalities of the R package soilphysics that can be used to fit and statistically compare five water retention curve models, based on uni‐ or bimodal pore size distribution, using different approaches, from command line to interactive and automatized tools in user‐friendly interfaces. The interactive approaches can also serve as didactic mechanisms, as they can help the user to understand how the water retention curve model fits the experimental data. soilphysics is freely available from the Comprehensive R Archive Network (CRAN; https://CRAN.R‐project.org/package=soilphysics). The functionalities presented here are available from versions 4.1 or later; some tools can also run online.

Ordered Mesoporous Boron Carbon Nitrides with Tunable Mesopore Nanoarchitectonics for Energy Storage and CO2 Adsorption Properties.

Porous boron carbon nitride (BCN) is one of the exciting systems with unique electrochemical and adsorption properties. However, the synthesis of low‐cost and porous BCN with tunable porosity is challenging, limiting its full potential in a variety of applications. Herein, the preparation of well‐defined mesoporous boron carbon nitride (MBCN) with high specific surface area, tunable pores, and nitrogen contents is demonstrated through a simple integration of chemical polymerization of readily available sucrose and borane ammonia complex (BAC) through the nano‐hard‐templating approach. The bimodal pores are introduced in MBCN by controlling the self‐organization of BAC and sucrose molecules within the nanochannels of the template. It is found that the optimized sample shows a high specific capacitance (296 F g−1 at 0.5 A g−1), large specific capacity for sodium‐ion battery (349 mAg h−1 at 50 mAh g−1), and excellent CO2 adsorption capacity (27.14 mmol g−1 at 30 bar). Density functional theory calculations demonstrate that different adsorption sites (B—C, B—N, C—N, and C—C) and the large specific surface area strongly support the high adsorption capacity. This finding offers an innovative breakthrough in the design and development of MBCN nanostructures for energy storage and carbon capture applications.

Facet effect on diverse WO3 morphologies and ideal work function for ppb-level triethylamine detection

Tungsten oxides with different crystal facet ratios were successfully prepared through one-spot solvothermal approach using alcohol solvents with different C chains accompanied by annealing treatment. The sensing performances for detecting triethylamine have been systematically investigated among the as-obtained WO3 samples. Benefiting from the unique microstructure with bimodal pores, the highest work function for the low-intensity ratio of the (002) WO3 facet, the smallest average crystallites sizes and abundant grain boundaries, the sensor based on WO3 microflowers assembled by tiny nanoparticles exhibits appealing sensing performance including high response, excellent selectivity, rapid response/recovery time (3 s/5 s) to 1 ppm triethylamine and extremely low detection limitation (200 ppb) at 325 °C.

Open-cell aluminum foams with bimodal pore size distributions for emerging thermal management applications

Recent advances in cellular materials for active thermal management applications involve the integral design of their porous structure. In this work, open-cell aluminum foams with porosities in the range of 0.60–0.76 are developed, containing pores with spherical geometry and a bimodal pore size distribution. The fabrication strategy involves the use of the replication method by infiltration with liquid aluminum of porous preforms formed by packing NaCl spheres of two largely different sizes (7 mm and 1 mm average diameter), which are then removed by water dissolution. The paper describes cellular materials with different proportions of coarse and fine pores. Their detailed characterization by pore volume fraction, pressure drop, permeability, thermal conductivity and heat transfer coefficient is supported by analytical schemes. In addition, these materials were characterized under realistic operating conditions using computational fluid dynamics simulations. The material with 67 percent coarse pores and 33 percent fine pores, which has the highest porosity (and thus permeability), has the most appealing heat dissipation properties with the lowest pressure drops, making it an excellent candidate for emerging thermal management applications in electronic systems.

Investigating the electrowetting of silver‐based gas‐diffusion electrodes during oxygen reduction reaction with electrochemical and optical methods

AbstractPorous gas‐diffusion electrodes (GDEs) are widely used in electrochemical applications where a gaseous reactant is converted to a target product. Important applications for silver‐based GDEs are the chlor‐alkali and the CO2 electrolysis processes in which silver catalyzes the oxygen‐ or carbon dioxide reduction reaction. The wetting of the porous GDEs is of utmost importance for the achieved performance of the electrode: a completely dry electrode will result in low current densities due to the reduced active surface area while on the other hand, a completely flooded electrode will deteriorate the access of the gaseous reactant. Therefore, we investigated silver‐based GDEs for the oxygen reduction reaction with different amounts of the hydrophobic agent polytetrafluoroethylene (PTFE) and analyzed the potential‐induced wetting behavior (electrowetting). The electrolyte breakthrough was recorded by a digital microscope and subsequently evaluated via imaging analysis of the observed breached electrolyte droplets. In order to characterize the wetting state during transition to the steady‐state, we applied electrochemical impedance spectroscopy measurements and retrieved the double‐layer capacitance. Our results indicate that a higher overvoltage facilitates the breakthrough of electrolytes through the gas‐diffusion electrode. Surprisingly, a faster breakthrough of electrolyte was observed for electrodes with higher PTFE content. Porometry measurements revealed that the GDE with low PTFE content has a monomodal pore size distribution, whereas electrodes with higher PTFE amount exhibit a bimodal pore size distribution. In GDEs with monomodal pore size distribution the time in which the double layer capacitance is leveling off correlates with the breakthrough time of the electrolyte. In summary, we emphasize that the wetting of GDEs is a complex interplay of the applied potential, electrode composition, and resulting porous structure which requires further advanced measurements and analysis considering the parameters affecting the wetting behavior as a whole.

Ginger and Garlic Extracts Enhance Osteogenesis in 3D Printed Calcium Phosphate Bone Scaffolds with Bimodal Pore Distribution.

Natural medicines have long been used to treat physiological ailments where both ginger (gingerol) and garlic (allicin) are key players in immune system promotion, reduction in blood pressure, and lowering inflammation response. With their efficacy in bone healing, these compounds have great value as medicinal additives in bone scaffolds for localized treatment to support tissue formation, along with providing their natural therapeutic benefits. Utilization of 3D-printed (3DP) bone tissue engineering scaffolds as drug delivery vehicles for ginger and garlic extracts enables patient specificity in bone defect applications with enhanced osseointegration. Our objective is to understand their combined efficacy on osteogenesis when released from 3DP calcium phosphate bone scaffolds designed with a bimodal pore distribution. With a porous core and dense exterior, the resulting scaffolds have good mechanical integrity with 10 ± 1 MPa compressive strengths. Results show that ginger + garlic extracts released from bone scaffolds enhance their osteogenic potential through on site drug delivery. Both compounds exhibit exponential drug release profiles which fit Weibull distribution equations. The release of ginger extract also increases osteoblast proliferation by 59%. Both compounds show decreased osteoclast resorption activity, with a greater than 20% reduction in pit area on sample surfaces. Ginger + garlic extract induces a twofold increase in early osteoid tissue formation in vivo at week 4, in addition to a 30% increase in total bone area and a 90% increase in osteocytes with respect to control 3DP tricalcium phosphate scaffolds. Late-stage bone healing at week 10 reveals healthy angiogenic tissue, a twofold higher bone mineralization, and significant enhancement of type I collagen formation in the presence of ginger and garlic extracts. Naturally sourced ginger and garlic extracts provide osteogenic promotion and improved bone tissue in-growth in a patient-specific 3DP scaffold biomedical device for low load-bearing bone tissue engineering and dental applications.

Copper nanoparticles decorated N-doped mesoporous carbon with bimodal pores for selective gas separation and energy storage applications

• Mesoporous N & Cu doped carbon materials with enhanced physico-chemical features. • Materials display redox, conducting, basic, adsorption and porous characteristics. • N/Cu doped carons show ordered structure with a bimodal pores size distribution. • High gas adsorption capacity and selectivity in a mixture of CO 2 /H 2 and CO 2 /CH 4. • High values for supercapacitance with good cyclic ability and capacitance retention. We demonstrate a synthesis of copper nanoparticles decorated over nitrogen-doped mesoporous carbon with different N and Cu contents which exhibit conducting, redox, basic, adsorption, and excellent textural properties. These materials are prepared through a nanotemplating approach by simultaneously encapsulating sucrose, guanidine hydrochloride, and Cu(NO 3 ) 2 into the porous channels of mesoporous SBA-15 at a low carbonization temperature of 600 °C. The prepared materials exhibit an ordered mesoporous carbon framework with bimodal pores, decorated with nitrogen and Cu functionalities on the surface of the pores and in the wall structure. The presence of nitrogen functionalities in the porous carbon matrix not only helps to reduce the Cu ions but also stabilizes the nanoparticles and offers redox sites, which are beneficial for adsorption and electrochemical applications. The optimized sample exhibits the highest adsorption capacity of different gases such as CO 2 – 22.5 mmol/g at 273 K, H 2 −13.5 mmol/g at 77 K at 30 bar and CH 4 − 5 mmol/g at 298 K and 50 bar. We also demonstrate that the prepared material shows a high selectivity of adsorption towards CO 2 in a mixture of CO 2 /H 2 and CO 2 /CH 4 and it also registers a high supercapacitance of 209 F g −1 at a current density of 1 A g −1 with excellent cyclic stability.

Ordered Dual-Channel carbon embedded with molybdenum nitride catalytically induced High-Performance Lithium-Sulfur battery

• MoN@CMK-5 with a bimodal pore was employed as polar host for sulfur cathode. • MoN@CMK-5/S shows an excellent inhibition effect for LiPSs. • The electrochemical reaction kinetics is effectively enhanced. • MoN@CMK-5/S delivers superior durability and a high charge capacity. Lithium-sulfur batteries (LSBs) have attracted considerable research attention because of their high theoretical capacity and energy density, low cost and environmental friendliness. However, the shuttle effect of lithium polysulfides hinders the commercialization of LSBs. Effectively improving the electrochemical reaction kinetics of the sulfur cathode still represents a significant challenge. Here, a MoN@CMK-5 composite with a bimodal pore system was designed to electrocatalytically mediate Li/S conversion chemistry. MoN@CMK-5 presents a large specific surface area (1012 m 2 g −1 ) and two sets of tunnels with pore sizes of 3.63 and 3.47 nm, which efficiently adsorb polysulfides and accelerate the mass transfer of electrolytes. Furthermore, MoN has high intrinsic catalytic activity and enables the rapid conversion of polysulfides. Owing to the synergistic “adsorption-conversion-mass transfer” effect, the electrochemical reaction kinetics are effectively enhanced. Consequently, the MoN@CMK-5/S electrode achieves excellent performance with an initial capacity of 1582 mAh g −1 at 0.1C and retains a reversible capacity of 658.4 mAh g −1 after 200 cycles at 1C. The cathode delivers a specific capacity of 475.8 mAh g −1 at a high current density of 5C, with a capacity decay as low as 0.027% per cycle during 1000 cycles. In addition, theoretical calculations reveal that MoN@CMK-5/S exhibits low activation energy for Li 2 S decomposition and effectively inhibits the shuttling of polysulfides. This work provides a new avenue for the development of high-performance LSBs.

Biomimetic Design of Macroporous 3D Truss Materials for Efficient Interfacial Solar Steam Generation.

Interfacial solar steam generation (ISSG) utilizing local heating technology for evaporation at the water-to-steam interface is drawing great attention because of its high efficiency of solar-thermal conversion for a sustainable and eco-friendly drinking water regeneration process. Here, inspired by the structure of penguin feathers and polar bear hairs that both have macropores to trap air for thermal insulation, we report a bionic solar evaporator (BSE) with macroporous skeleton for partial thermal management and macro patulous channels for abundant water transportation and rapid steam extraction. Meanwhile, the 3D hierarchical isotropic truss structures can induce multiple light reflections to enable omnidirectional light absorption, and bimodal pores facilitate ion diffusion to suppress salt deposits. This BSE exhibits an evaporation rate of 2.3 kg m-2 h-1 and efficiency of 93% under 1 sun. The multiple advantages of high efficiency and salt resistance make BSE available for future practical sewage purification and desalination applications.

Oxygen defective bimodal porous Ni-CeO2−x-MgO-Al2O3 catalyst with multi-void spherical structure for CO2 reforming of CH4

Ni-CeO2-MgO-Al2O3 catalysts with bimodal meso-macropores have been synthesized by one-pot spray pyrolysis using dextrin as a structuring agent for dry reforming of methane. The formation of macropores originating from phase segregation and the decomposition of dextrin positively affects both the physical and chemical features of the catalysts, and therefore, the bimodal porous catalysts outperform the dense catalysts in catalytic activity and stability. The volume and size of macropores in a bimodal porous catalyst are dependent on the concentration of dextrin. Based on diverse characterization results, this morphological change has been revealed to induce the distortion of the CeO2 lattice and embedding of Ni nanoparticles, resulting in the strong interaction between the metal and support/promoter and high oxygen storage capacity. The catalyst with balanced bimodal pore structures and optimized physicochemical parameters showed the best performance, considering both catalytic activity and stability with high sintering/coking resistance in the dry reforming of methane.

The fabric evaluation of two Indian bentonites subjected to different suctions and consolidation pressures

The study highlighted the fabric evaluation (i.e., pore size distribution (PSD) and morphology) of monovalent and divalent Indian bentonites, subjected to different suctions and consolidation pressures. Oedometer tests were conducted on bentonites specimens in two different initial conditions, i.e., slurry and compacted conditions. The slurry and compacted specimens were prepared at water contents equal to liquid limit (LL) and optimum moisture content (OMC), respectively. The water retention properties of the bentonites were determined in both unconfined (slurry) and confined (compacted) conditions using pressure plate apparatus and WP4C dew-point potentiameter. The influence of different consolidation pressures and suctions on pore structure and morphology of the bentonites were investigated by mercury intrusion porosimetry (MIP) and Field Emission Scanning Electron Microscope (FESEM) observations. For both the bentonites, the bimodal pore size distribution was observed over the applied consolidation pressure between 7.2 kPa and 2289.6 kPa in both slurry and compacted specimen conditions. However, an increase in consolidation pressure lead to a significant decrease in macropore volume. The compression index of the bentonites was found to be strongly correlated with a percentage decrease in macropore intruded volume (R2 = 0.91) and total intruded pore volume (R2 = 0.89), however, independent of micropores volume. The FESEM images and MIP results evidenced that for both the bentonites more homogeneous morphology and effective filling of the pores took place in slurry conditions as compared to initially compacted specimens. For the same void ratio, the hydraulic conductivity of slurry specimens was noted to be slightly lower than the compacted specimens. In slurry conditions at suctions below 3 MPa, the water retention capacity of monovalent bentonite was noted to be higher than that of divalent bentonite, whereas the opposite trend was found in compacted conditions. Irrespective of slurry or compacted conditions, the increase in suction lead to the transformation of bimodal PSD into a unimodal pore family for divalent bentonite, whereas trimodal to unimodal PSD was noted for monovalent bentonite in compacted specimens. The initial state (slurry or compacted) and the boundary condition of the specimen, as well as fabric (pore size distribution and morphology) of the bentonites, were found to have a notable influence on the compressibility, hydraulic conductivity and water retention properties.

High CO2 adsorption on amine-functionalized improved macro-/mesoporous multimodal pore silica

In recent years, amine functionalized materials have attracted great interest as prospective solid adsorbents for CO2 capture. However, the amine functionalization of traditional supports (such as SBA-15, etc.) can lead to a decrease in the pore volume and specific surface area of the adsorbent, which significantly affects the CO2 adsorption–desorption kinetics. To overcome this problem, the macro-/mesoporous multimodal pore silica was quickly synthesized using a ternary nonionic surfactant as a template through a partitioned collaborative self-assembly method, and impregnated with TEPA. The prepared support HMS-4 h has bimodal pores (pore size of 9.41 nm and 90 nm), which can not only improve the dispersibility of the loaded TEPA, but also effectively reduce the diffusion resistance of CO2. At the same time, the high surface area (838 m2/g) and large pore volume (2.34 cm3/g) of HMS-4 h can further improve the adhesion and quantity of amine-based active sites. The highest adsorption capacity reaches 6.04 mmol/g for HMS-4 h-75%TEPA at 90 ℃ and 1 bar. The adsorption capacity for HMS-4 h-75%TEPA was steady after 10 adsorption–desorption cycles. BET, XRD, FT-IR, SEM, TG-DTG were used to characterize the performance of the adsorbent. The CO2 adsorption mechanism and the effects of organic amine loading, adsorption temperature and CO2 concentration on CO2 adsorption performance were systematically studied. The research shows that HMS-4 h-75%TEPA is an excellent adsorbent with high adsorption capacity in a wide temperature range, and low energy. This provides a reference for the design of high-performance solid amine CO2 adsorbents in the future.

Novel Insight into the Concept of Favorable Combination of Electrodes in High Voltage Supercapacitors: Toward Ultrahigh Volumetric Energy Density and Outstanding Rate Capability.

Most of the biomass‐derived carbon‐based supercapacitors using organic electrolytes exhibit very low energy density due to their low operating potential range between 2.7 and 3.0 V. A novel insight into the concept of the different porous architecture of electrode materials that is employed to extend a device's operating potential up to 3.4 V using TEABF4 in acetonitrile, is reported. The combination of two high surface area activated carbons derived from abundant natural resources such as industrial waste cotton and wheat flour as sustainable and green carbon precursors is explored as an economical and efficient supercapacitor carbon electrode. Benefitting from the simultaneous achievement of the higher potential window (3.4 V) with higher volumetric capacitance (101 F cm–3), the supercapacitor electrodes exhibit higher volumetric energy density (42.85 Wh L–1). Bimodal pore size distribution of carbon with a tuned pore size and high specific surface area of the electrode can promote the fast transport of cations and anions. Hence, it exhibits a high rate capability even at 30 A g–1. In addition, the electrodes remain stable during operation cell voltage at 3.4 V upon 15 000 charging–discharging cycles with 90% capacitance retention.