Macroporous 3D Research Articles

Transmission Characteristics of the Macropore Flow in Vegetated Slope Soils and Its Implication for Slope Stability

Macropores in the soil of vegetated slopes greatly affect the rainfall infiltration process. In this paper, a realistic 3D macropore network model of a soil column sample is established by CT scanning. Then, the transmission process of the macropore flow is simulated based on MODFLOW. The results show that (1) the shapes of macropores in the soil contain not only the dominant proportion of the circular tube but also a small proportion of the flake. (2) The velocity of macropore flow has a maximum of up to 0.2~0.3 m/s, which is much higher than that of matrix flow. In every single macropore, the flow velocity is the greatest at the central axis perpendicular to the extension and at the throat along the extension. (3) Due to the development of the macropore network system, rainwater can quickly pass through the soil profile in the form of preferential flow or pipe flow, which shortens the lag time of the peak discharge response to rainfall. This process can free up space for the next recharge, but reduce the overall quality of the soil, laying the foundation for the slope failure. Our work helps to unravel the mechanism of rainfall-induced landslides and promote harmony and sustainable development between humans and nature.

Biomimetic mineralization of platelet lysate/oxidized dextran cryogel as a macroporous 3D composite scaffold for bone repair

Scaffold development approaches using autologous sources for tissue repair are of great importance in obtaining bio-active/-compatible constructs. Platelet-rich plasma (PRP) containing various growth factors and platelet lysate (PL) derived from PRP are autologous products that have the potential to accelerate the tissue repair response by inducing a transient inflammatory event. Considering the regenerative capacity of PRP and PL, PRP/PL-based scaffolds are thought to hold great promise for tissue engineering as a natural source of autologous growth factors and a provider of mechanical support for cells. Here, a bio-mineralized PRP-based scaffold was developed using oxidized dextran (OD) and evaluated for future application in bone tissue engineering. Prepared PL/OD scaffolds were incubated in simulated body fluid (SBF) for 7, 14 and 21 d periods. Mineralized PL/OD scaffolds were characterized using Fourier transform infrared spectroscopy, x-ray diffraction spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis, porosity and compression tests. SEM and energy-dispersive x-ray spectroscopy analyses revealed mineral accumulation on the PL/OD scaffold as a result of SBF incubation. In vitro cytotoxicity and in vitro hemolysis tests revealed that the scaffolds were non-toxic and hemocompatible. Additionally, human osteoblasts (hOBs) exhibited good attachment and spreading behavior on the scaffolds and maintained their viability throughout the culture period. The alkaline phosphatase activity assay and calcium release results revealed that PL/OD scaffolds preserved the osteogenic properties of hOBs. Overall, findings suggest that mineralized PL/OD scaffold may be a promising scaffold for bone tissue engineering.

A smart thermoresponsive macroporous 4D structure by 4D printing of Pickering-high internal phase emulsions stabilized by plasma-functionalized starch nanomaterials for a possible delivery system

Hierarchically porous structures combine microporosity, mesoporosity, and microporosity to enhance pore accessibility and transport, which are crucial to develop high performance materials for biofabrication, food, and pharmaceutical applications. This work aimed to develop a 4D-printed smart hierarchical macroporous structure through 3D printing of Pickering-type high internal phase emulsions (Pickering-HIPEs). The key was the utilization of surface-active (hydroxybutylated) starch nanomaterials, including starch nanocrystals (SNCs) (from waxy maize starch through acid hydrolysis) or starch nanoparticles (SNPs) (obtained through an ultrasound treatment). An innovative procedure to fabricate the functionalized starch nanomaterials was accomplished by grafting 1,2-butene oxide using a cold plasma technique to enhance their surface hydrophobicity, improving their aggregation, and thus attaining a colloidally stabilized Pickering-HIPEs with a low concentration of each surface-active starch nanomaterial. A flocculation of droplets in Pickering-HIPEs was developed after the addition of modified SNCs or SNPs, leading to the formation of a gel-like structure. The 3D printing of these Pickering-HIPEs developed a highly interconnected large pore structure, possessing a self-assembly property with thermoresponsive behavior. As a potential drug delivery system, this thermoresponsive macroporous 3D structure offered a lower critical solution temperature (LCST)-type phase transition at body temperature, which can be used in the field of smart releasing of bioactive compounds.

In Situ Sol-Gel Assembly of Graphitic Carbonitride Nanosheet-Supported Colloidal Binary Metal Sulfide into Nanosandwich-Like Multifunctional 3D Macroporous Aerogel Catalysts for Asymmetric Supercapacitor and Electrocatalytic Oxygen and Hydrogen Evolution

It is challenging to develop scalable and stable multifunctional catalysts for energy storage and conversion applications. To address the above challenges, we designed 3D macroporous nanosandwich-like aerogels using an in situ sol-gel assembly for 2D g-C3N4 nanosheet-supported NiCo2S4 nanoporous aerogels. The resultant in situ method not only assembles NiCo2S4 but also 2D g-C3N4 into the sandwich-like 3D network, allowing rapid ion and electron transport. The potential of g-C3N4 and NiCo2S4 in electrochemical energy storage and electrocatalysis is promising for improving its electrochemical activities. The synthesized 3D NiCo2S4/g-C3N4 (3%) composite aerogel electrode achieved a remarkable specific capacitance value, 1083 F·g-1 at 5 mA·cm-2 current density with 87.03% cyclic stability. Furthermore, the asymmetric electrochemical supercapacitor device was fabricated with a maximum specific energy of 43 Wh·kg-1, with outstanding electrochemical stability of about 97% over 10,000 charge/discharge cycles. In addition, NiCo2S4/g-C3N4 (3%) catalysts achieved 294 and 155 mV as oxygen and hydrogen evolution reaction overpotentials, respectively, at 20 and 10 mA·cm-2 current density values. This study provides a new method for the conversion of 2D sheets and 0D colloidal network into 3D macroporous nanocomposite aerogels in multifunctional applications.

3D Macroporous and Mesoporous Sponge for Selective Pollutant Removal

3D Macroporous and Mesoporous Sponge for Selective Pollutant Removal

Internal surface modification of additively manufactured macroporous TiAl6V4 biomimetic implants via a calciothermic reaction-based process and osteogenic in vivo responses.

Three-dimensional macroporous titanium-aluminum-vanadium (TiAl6V4) implants produced by additive manufacturing (AM) can be grit blasted (GB) to yield microtextured exterior surfaces, with additional micro/nano-scale surface features provided by subsequent acid etching (AE). However, the line-of-sight nature of GB causes the topography of exterior GB + AE-modified surfaces to differ from internal GB-inaccessible surfaces. Previous in vitro studies using dense TiAl6V4 substrates indicated that a nonline-of-sight, calciothermic-reaction (CaR)-based process provided homogeneous osteogenic nanotextures on GB + AE surfaces, suggesting it could be used to achieve a homogeneous nanotopography on external and internal surfaces of macroporous AM constructs. Macroporous TiAl6V4 (3D) constructs were produced by direct laser melting and modified by GB + AE, with the CaR process then applied to 50% of constructs (3DCaR). The CaR process yielded nanoporous/nanorough internal surfaces throughout the macroporous constructs. Skeletally mature, male Sprague-Dawley rats were implanted with these constructs using a cranial on-lay model. Prior to implantation, a Cu++-free click hydrogel was applied to half of the constructs (3D + H, 3DCaR + H) to act as a challenge to osseointegration. Osseointegration was compared between the four implant groups (3D, 3DCaR, 3D + H, 3DCaR + H) at 4w. 3D + H implants exhibited lower bone volume (BV) and percent bone ingrowth (%BI) than the 3D implants. In contrast, osseointegrated 3DCaR + H implants had similar BV and %BI as the 3DCaR implants. Implant pull-off forces correlated with these results. In vitro analyses indicated that human bone marrow stromal cells (MSCs) exhibited enhanced production of osteoblast differentiation markers and factors associated with osteogenesis when grown on CaR-modified 3D substrates relative to control (TCPS) substrates. This work confirms that the CaR process provides osteogenic nanotextures on internal surfaces of macroporous 3D implants, and suggests that CaR-modified surfaces can promote osseointegration in cases where osteogenesis is impaired.

Rapid Prototyping of 3D-Printed AgNPs- and Nano-TiO2-Embedded Hydrogels as Novel Devices with Multiresponsive Antimicrobial Capability in Wound Healing.

Two antimicrobial agents such as silver nanoparticles (AgNPs) and titanium dioxide (TiO2) have been formulated with natural polysaccharides (chitosan or alginate) to develop innovative inks for the rapid, customizable, and extremely accurate manufacturing of 3D-printed scaffolds useful as dressings in the treatment of infected skin wounds. Suitable chemical-physical properties for the applicability of these innovative devices were demonstrated through the evaluation of water content (88-93%), mechanical strength (Young's modulus 0.23-0.6 MPa), elasticity, and morphology. The antimicrobial tests performed against Staphylococcus aureus and Pseudomonas aeruginosa demonstrated the antimicrobial activities against Gram+ and Gram- bacteria of AgNPs and TiO2 agents embedded in the chitosan (CH) or alginate (ALG) macroporous 3D hydrogels (AgNPs MIC starting from 5 µg/mL). The biocompatibility of chitosan was widely demonstrated using cell viability tests and was higher than that observed for alginate. Constructs containing AgNPs at 10 µg/mL concentration level did not significantly alter cell viability as well as the presence of titanium dioxide; cytotoxicity towards human fibroblasts was observed starting with an AgNPs concentration of 100 µg/mL. In conclusions, the 3D-printed dressings developed here are cheap, highly defined, easy to manufacture and further apply in personalized antimicrobial medicine applications.

3D characterization of localized shear failure in loess subject to triaxial loading

The reduction of shear strength of loess slopes is generally driven by localized failure in loess that lowers the trigger thresholds of major landslide geohazards in these materials. Shear failure is initially manifested as discontinuous microscale fractures that progressively develop into macroscale rupture surfaces. In this study, the development of localized shear failure in Malan loess is investigated through an approach combining laboratory triaxial shear test and X-ray micro-computed tomography (μ-CT). The spatial distribution and morphological evolution of fractures associated with the shear failure plane are observed at different loading stages in a non-destructive manner. It is found that, with ongoing strain, the number and persistence of multiple undulating fracture surfaces gradually increase after peak strength condition are reached until a single, dominant shear failure plane is formed. Most fracture surfaces are oblique to the major principal stress direction forming a shear band of finite thickness. Within this band it is possible to observe zones where varying strain magnitude is accommodated by a network of fracture surfaces. The effect of strain accumulation and local shear failure on the sample's macroporosity was determined by performing calculations on the CT images of each loading stage. Whereas the bulk sample underwent a reduction in macroporosity as a result of the triaxial compression, movement along undulating fracture surfaces results in the opening (and closing) of apertures with ongoing shear strain within a shear band of finite thickness. The overall result is an increase in macroporosity in this shear band with an estimated thickness of approximately 5 mm. Image analysis also allows characterization of changes in the 3D macropore network of the original loess fabric. Macropore network can be disconnected, dislocated and even destroyed when affected by shear failure development. These morphological variations of macropores serve as benchmarks that indicate the early initiation and expanding range of local shear failure and also allow the evaluation of the effect of local shear failure on seepage characteristics. The results of this study could provide important insights into multi-scale modelling of mechanical behaviour of loess.

3D Macroporous Frame Based Microbattery With Ultrahigh Capacity, Energy Density, and Integrability

AbstractIn‐plane microbatteries (MBs) with features of facile integration, mass customization, and especially superior electrochemical performance are urgently required for self‐powered microelectronic devices. In this work, a facile manufacturing process is employed to fabricate Zn–MnO2 MB with a 3D macroporous microelectrode. Benefiting from the high electron/ion transport path of 3D macroporous microelectrode and high mass‐loading of poly(3,4‐ethylenedioxythiophene)‐manganese dioxide (PEDOT‐MnO2) film, the MB achieves an ultrahigh capacity of 0.78 mAh cm−2 and an outstanding areal energy density of 1.02 mWh cm−2. Moreover, 3D macroporous PEDOT‐MnO2 hybrid film is achieved by one‐step electrodeposition, which effectively improves the cycling performance without reducing areal capacity or hindering the ion diffusion. Notably, the MB can stably drive an electronic timer for ≈400 min or be integrated and operated on the surface of a digital hygro‐thermometer. The MBs are capable of operating stably in the high rotation speed and vibration condition, such as applied on the surface of an axial‐flow fan. Moreover, the MB can integrate by stacking the substrate‐free microelectrodes and achieving outstanding energy density of 3.87 mWh cm−2. Therefore, the PEDOT‐MnO2//Zn MB has good prospects as a next‐generation component applied in self‐powered microelectronic devices.

GOING LOW: LOW MODULUS GRAFT-FREE 3D-PRINTED TITANIUM INTERBODY CAGES SHOW COMPARABLE BONE FORMATION TO PEEK WITH GRAFT

Polyetheretherketone (PEEK) interbody fusion cages combined with autologous bone graft is the current clinical gold standard treatment for spinal fusion, however, bone graft harvest increases surgical time, risk of infection and chronic pain. We describe novel low-stiffness 3D Printed titanium interbody cages without autologous bone graft and assessed their biological performance in a pre-clinical in vivo interbody fusion model in comparison to the gold standard, PEEK with graft.Titanium interbody spacers were 3D Printed with a microporous (Ti1: <1000μm) and macroporous (Ti2: >1000μm) design. Both Ti1 and Ti2 had an identical elastic modulus (stiffness), and were similar to the elastic modulus of PEEK. Interbody fusion was performed on L2-L3 and L4-L5 vertebral levels in 24 skeletally mature sheep using Ti1 or Ti2 spacers, or a PEEK spacer filled with iliac crest autograft, and assessed at 8 and 16 weeks. We quantitatively assessed bone fusion, bone area, mineral apposition rate and bone formation rate. Functional spinal units were biomechanically tested to analyse range of motion, neutral zone, and stiffness. Results: Bone formation in macroporous Ti2 was significantly greater than microporous Ti1 treatments (p=.006). Fusion scores for Ti2 and PEEK demonstrated greater rates of bone formation from 8 to 16 weeks, with bridging rates of 100% for Ti2 at 16 weeks compared to just 88% for PEEK and 50% for Ti1. Biomechanical outcomes significantly improved at 16 versus 8 weeks, with no significant differences between Ti and PEEK with graft.This study demonstrated that macroporous 3D Printed Ti spacers are able to achieve fixation and arthrodesis with complete bone fusion by 16 weeks without the need for bone graft. These significant data indicate that low-modulus 3D Printed titanium interbody cages have similar performance to autograft-filled PEEK, and could be reliably used in spinal fusion avoiding the complications of bone graft harvesting.

Ordered Macro-Microporous Single Crystals of Covalent Organic Frameworks with Efficient Sorption of Iodine.

Fashioning microporous covalent organic frameworks (COFs) into single crystals with ordered macropores allows for an effective reduction of the mass transfer resistance and the maximum preservation of their intrinsic properties but remains unexplored. Here, we report the first synthesis of three-dimensional (3D) ordered macroporous single crystals of the imine-linked 3D microporous COFs (COF-300 and COF-303) via a template-assisted modulated strategy. In this strategy, COFs crystallized within the sacrificial colloidal crystal template, assembled from monodisperse polystyrene microspheres, and underwent an aniline-modulated amorphous-to-crystalline transformation to form large single crystals with 3D interconnected macropores. The effects of the introduced macroporous structure on the sorption performances of COF-300 single crystals were further probed by iodine. Our results indicate that iodine adsorption occurred in micropores of COF-300 but not in the introduced macropores. Accordingly, the iodine adsorption capacity of COF single crystals was governed by their micropore accessibility. The relatively long diffusion path in the non-macroporous COF-300 single crystals resulted in a limited micropore accessibility (48.4%) and thus a low capacity in iodine adsorption (1.48 g·g-1). The introduction of 3D ordered macropores can greatly shorten the microporous diffusion path in COF-300 single crystals and thus render all their micropores fully accessible in iodine adsorption with a capacity (3.15 g·g-1) that coincides well with the theoretical one.

One-pot synthesis of a CaBi2O4/graphene hybrid aerogel as a high-efficiency visible-light-driven photocatalyst

At present, the development of broad-spectrum and visible-light-driven photocatalysts is highly desirable for sewage treatment, which is due to the serious environmental pollution in the world. A CaBi2O4/graphene aerogel (CaBi2O4/GA), as a high-efficiency photocatalyst, has in the present study been successfully prepared using a one-pot hydrothermal method combined with a freeze-drying process. The as-prepared CaBi2O4/GA composite exhibited a macroporous three-dimensional (3D) network structure with lamellar CaBi2O4 particles distributed on the graphene sheets. Considering the wide range of visible-light absorption and a suitable band gap, CaBi2O4/GA has here been explored as a plausible photocatalyst for the degradation of several dyes and antibiotic drugs. Under visible light irradiation for 120 min, the photodegradation efficiencies were found to be 93.37%, 87.16%, 91.69%, and 93.25% for methyl orange, rhodamine B, methylene blue, and tetracycline hydrochloride, respectively. For dye/drug wastewater solutions under real sunlight irradiation, CaBi2O4/GA showed a high degradation efficiency. In fact, CaBi2O4/GA exhibited an improved photodegradation activity compared to pure CaBi2O4 and CaBi2O4/graphene. Based on the measurements of photoluminescence spectra and electrochemical impedance spectra, the photocatalytic mechanism of CaBi2O4/GA was proposed to clarify its photodegradation process. Trapping tests indicated that the ·O2− radicals played a key role in the photocatalytic reaction as a dominant reactive species. The advantage of a macroporous 3D structure, suitable band gap, high photodegradation efficiency, and cyclic stability promotes the practical applications of CaBi2O4/GA as a high-efficiency visible-light-driven photocatalyst in wastewater treatment.

Annealing High Aspect Ratio Microgels into Macroporous 3D Scaffolds Allows for Higher Porosities and Effective Cell Migration (Adv. Healthcare Mater. 24/2022)

Annealing High Aspect Ratio Microgels into Macroporous 3D Scaffolds Allows for Higher Porosities and Effective Cell Migration (Adv. Healthcare Mater. 24/2022)

Rational design of graphite carbon nitride-decorated zinc oxide nanoarrays on three-dimensional nickel foam for the efficient production of reactive oxygen species through stirring-promoted piezo–photocatalysis

Stirring-promoted piezo–photocatalysis based on a three-dimensional foam architecture has great potential applications in wastewater treatment and water splitting. However, the detailed mechanism of stirring-promoted piezo–photocatalysis has not been quantitatively studied, and the utilization of visible light needs to be further improved. In this work, the high solar-driven piezo–photocatalytic ability of graphite carbon nitride (g-C3N4)-decorated zinc oxide (ZnO) nanoarrays on nickel (Ni) foam is experimentally achieved and first simulated by the finite element method (FEM). The water flow velocity, depending on the stirring rate, is significantly increased by turbulence-induced fluid eddies while flowing through 3D macropores and nanoarrays, resulting in higher piezoelectricity. Reactive oxygen species (ROS) are experimentally examined by the electron spin resonance (ESR) technique and theoretically calculated by density functional theory (DFT) to confirm the configurations of the heterojunction under photocatalysis and piezo–photocatalysis. In particular, the large enhancement of 1O2 generation suggests the potential of piezo–photocatalysis in biological applications. The mechanism of piezo–photocatalysis is proposed in which the S-scheme heterojunction is realized by piezoelectricity to improve photocatalysis by retaining high redox ability and inhibiting recombination. This work provides a possible approach to harvesting energy sources for piezoelectricity and expands the scope of solar-driven piezo–photocatalysis.

Macroporous 3D printed structures for regenerative medicine applications

The use of natural biopolymers as a core material to produce cell-laden scaffolds has been recognized and extensively utilized for tissue engineering purposes due to their advantageous biocompatibility and tunable biodegradation rate. The morphology and average pore size play, however, a major role in biological processes affecting cell proliferation kinetics as well as tissue regeneration processes associated with extracellular matrix formation. Shear thinning properties of the inks employed in 3D printing for high-accuracy hydrogel scaffold fabrication are often associated with compromises in morphology, such as reduced pore sizes. Here, we report on a carefully optimized composite formulation of (1:1) gelatin/oxidized alginate (Gel/OxAlg) that allows combining 3D printing and cryogelation techniques for simple and low-cost fabrication of biocompatible hydrogel scaffolds, characterized by high porosity and extra-large pore size (d > 100 μm). Based on the morphological characteristics and obtained cell viability data, the fabricated scaffolds might be used as a platform for a variety of tissue engineering applications.

Annealing High Aspect Ratio Microgels into Macroporous 3D Scaffolds Allows for Higher Porosities and Effective Cell Migration.

Growing millimeter-scaled functional tissue remains a major challenge in the field of tissue engineering. Therefore, microporous annealed particles (MAPs) are emerging as promising porous biomaterials that are formed by assembly of microgel building blocks. To further vary the pore size and increase overall MAP porosity of mechanically stable scaffolds, rod-shaped microgels with high aspect ratios up to 20 are chemically interlinked into highly porous scaffolds. Polyethylene glycol based microgels (width 10µm, lengths up to 200µm) are produced via in-mold polymerization and covalently interlinked into stable 3D scaffolds via epoxy-amine chemistry. For the first time, MAP porosities can be enhanced by increasing the microgel aspect ratio (mean pore sizes ranging from 39 to 82µm, porosities from 65 to 90%). These porosities are significantly higher compared to constructs made from spherical or lower aspect ratio rod-shaped microgels. Rapid filling of the pores by either murine or primary human fibroblasts is ensured as cells migrate and grow extensively into these scaffolds. Overall, this study demonstrates that highly porous, stable macroporous hydrogels can be achieved with a very low partial volume of synthetic, high aspect ratio microgels, leading to large empty volumes available for cell ingrowth and cell-cell interactions.

Redistributing interfacial charge density of Ni12P5/Ni3P via Fe doping for ultrafast urea oxidation catalysis at large current densities

Large-scale industrial application of urea electrolysis has prompted one to explore inexpensive and efficient urea oxidation reaction (UOR) catalysts that can achieve large current densities (≥500 mA cm−2) at relatively low potentials. In response, for the first time the robust UOR catalysts are developed via in-situ construction of the Fe-doped Ni12P5/Ni3P heterojunction nanosheets on the macroporous 3D NiFe foam skeleton (denoted as Fe-(Ni12P5/Ni3P)). The introduction of Fe element can not only strengthen the interfacial electric field and induce the spontaneous charge redistribution for heterogeneous Ni12P5/Ni3P, but also effectively lower the reaction energy barrier during stepwise UOR process. Benefiting from the unique ultra-thin nanosheets and the optimized electronic structure, the well-designed Fe-(Ni12P5/Ni3P) possesses more exposed active sites and faster electron and mass transfer, thus exhibiting superior catalytic UOR activity. Encouragingly, the Fe-(Ni12P5/Ni3P) can deliver the industrial-level current density of 800 mA cm−2 just at 1.4 V as well as a splendid Tafel slope of 28.2 mV dec−1. This catalyst also manifests remarkable durability under high current densities. As a consequence, our work opens up a brand-new-path in rational design of excellent UOR catalysts with high activity and stability to enable energy-saving electrolytic hydrogen production on industrial scale.

Recycled ZnO‐fused macroporous 3D graphene oxide aerogel composites for high‐performance asymmetric supercapacitors

AbstractIn the arena of energy storage device, asymmetric supercapacitors (ASCs) are considered a key category due to its high‐power density and energy densities. In this study, a novel macroporous microrecycled ZnO nanoparticles (mi‐ZnO NPs) recovered from spent Zn–C battery‐decorated three‐dimensional graphene aerogel (GA) composite has been synthesized via simple eco‐friendly synthetic method, which is used as a proficient anode material to fabricate ASC. The interconnected macroporous networks and ∼40‐nm microrecycled ZnO NPs incorporated GA (mi‐ZnO–GA) enhanced the surface area of anode materials, which lead to achieve a formation of high‐performance ASC. Here, we composed ASCs from a microrecycled ZnO thin film (cathode) and mi‐ZnO–GA composite (anode), which reveals fast charging/discharging characteristics, stable widen cell voltage, superior power, and energy densities (13.7 W h/kg, 13.2 kW/kg), and finally stable cyclability (76.8% retention after 5000 cycles). These outcomes open up the window for microrecycled ZnO NPs incorporated GA (mi‐ZnO–GA) as a prominent anode material for high‐performance energy storage devices.

Selective Catalytic Electro-Oxidation of Water with Cobalt Oxide in Ion Impermeable Reduced Graphene Oxide Porous Electrodes.

The direct electrolysis of seawater is greatly inhibited by the oxidation of Cl- to free chlorine, an undesirable, corrosive byproduct. To suppress the parasitic interference of Cl- and any other ion, we developed a freestanding, electrically conducting, 3D macroporous reduced graphene oxide (rGO) scaffold with cobalt oxide particles selectively deposited on the internal walls of its closed pores (with an average diameter of ∼180 μm). The pore walls act as membranes composed of stacked rGO flakes; the nanochannels between rGO layers (size <1 nm) are permeable to water and gases while preventing the diffusion of dissolved ions such as Cl-. Due to this, the catalytic particles are selectively accessible to water molecules but not to ions, allowing electrolysis to occur without chlorine evolution. The electrodes developed exhibit a stable generation of O2 from simulated seawater at pH 14, reaching a specific current density of up to 25 A g-1 during continuous electrolysis with 89-98% Faradaic efficiency, while chlorine generation is below 6 ppm h-1, the sensitivity limit of the detection method employed. The strategy here proposed can be generalized to build electrodes that are inherently selective thanks to their architecture, with catalytically active particles loaded into closed pores with selective ion transport properties.

Agarose Gel-Templating Synthesis of a 3D Wrinkled Graphene Architecture for Enhanced Supercapacitor Performance.

The increasing use of rapidly fluctuating renewable energy sources, such as sunlight, has necessitated the use of supercapacitors, which are a type of energy storage system with high power. Chemically exfoliated graphene oxide (GO) is a representative starting material in the fabrication of supercapacitor electrodes based on reduced GO (rGO). However, the restacking of rGO sheets driven by π–π stacking interactions leads to a significant decrease in the electrochemically active surface area, leading to a loss of energy density. Here, to effectively inhibit restacking and construct a three-dimensional wrinkled structure of rGO (3DWG), we propose an agarose gel-templating method that uses agarose gel as a soft and removable template. The 3DWG, prepared via the sequential steps of gelation, freeze-drying, and calcination, exhibits a macroporous 3D structure and 5.5-fold higher specific capacitance than that of rGO restacked without the agarose template. Further, we demonstrate a “gel-stamping” method to fabricate thin-line patterned 3DWG, which involves the gelation of the GO–agarose gel within micrometer-sized channels of a customized polydimethylsiloxane (PDMS) mold. As an easy and low-cost manufacturing process, the proposed agarose gel templating method could provide a promising strategy for the 3D structuring of rGO.