3D Porous Architecture Research Articles

Carbon Quantum Dots Derived N-Doped Porous Carbon Frameworks with High Electrocatalytic for Oxygen Reduction Reaction

Developing low-cost, high-performance metal-free oxygen reduction reaction (ORR) catalysts for fuel cells is highly desirable but still full of challenges. In this study, nitrogen-doped three-dimensional (3D) porous carbon frameworks (NCFs) derived from zero-dimensional carbon quantum dots have been prepared by a simple one-step self-assembly technique. The resultant NCF-800 (carbonized at 800[Formula: see text]C) possesses unique 3D porous framework architecture, large specific surface area (171[Formula: see text]cm2g[Formula: see text] and abundant defect sites. As a catalyst for ORR, the optimized NCF-800 displays a positive onset potential at 0.87[Formula: see text]V (versus reversible hydrogen electrode), which is roughly 60[Formula: see text]mV more negative than that of Pt/C (0.93[Formula: see text]V). Additionally, the NCF-800 exhibits long-term stability and strong endurance to methanol in alkaline electrolyte, which is much superior to those of Pt/C. Considering the outstanding activity of NCF-800, it can be worked as a prospective metal-free ORR catalyst for fuel cells in the future.

Two-Dimensional Hallmark of Highly Interconnected Three-Dimensional Nanoporous Graphene.

Scaling graphene from a two-dimensional (2D) ideal structure to a three-dimensional (3D) millimeter-sized architecture without compromising its remarkable electrical, optical, and thermal properties is currently a great challenge to overcome the limitations of integrating single graphene flakes into 3D devices. Herewith, highly connected and continuous nanoporous graphene (NPG) samples, with electronic and vibrational properties very similar to those of suspended graphene layers, are presented. We pinpoint the hallmarks of 2D ideal graphene scaled in these 3D porous architectures by combining the state-of-the-art spectromicroscopy and imaging techniques. The connected and bicontinuous topology, without frayed borders and edges and with low density of crystalline defects, has been unveiled via helium ion, Raman, and transmission electron microscopies down to the atomic scale. Most importantly, nanoscanning photoemission unravels a 3D NPG structure with preserved 2D electronic density of states (Dirac cone like) throughout the porous sample. Furthermore, the high spatial resolution brings to light the interrelationship between the topology and the morphology in the wrinkled and highly bent regions, where distorted sp2 C bonds, associated with sp3-like hybridization state, induce small energy gaps. This highly connected graphene structure with a 3D skeleton overcomes the limitations of small-sized individual graphene sheets and opens a new route for a plethora of applications of the 2D graphene properties in 3D devices.

Electrochemical performance of 3D porous Ni-Co oxide with electrochemically exfoliated graphene for asymmetric supercapacitor applications

Ni-Co oxide, one of the binary metal oxides, has many advantages for use in high-performance supercapacitor electrode materials due to its relatively high electronic conductivity and improved electrochemical performance. In this work, Ni-Co oxide/electrochemically exfoliated graphene nanocomposites (NC-EEG) are successfully synthesized using a simple low temperature solution method combined with a thermal annealing treatment. Graphene sheets are directly obtained by an electrochemical exfoliation process with graphite foil, which is very simple, environmentally friendly, and has a relatively short reaction time. This electrochemically exfoliated graphene (EEG) can improve the electrical conductivity of the Ni-Co oxide nanostructures. The as-prepared NC-EEG nanocomposites have 3D porous architectures that can provide large surface areas and shorten electron diffusion pathways. Electrochemical properties were performed by cyclic voltammetry and galvanostatic charge/discharge in a 6M KOH electrolyte. The NC-EEG nanocomposites exhibited a high capacity value of 649Cg−1 at a current density of 1.0Ag−1. The asymmetric supercapacitors, manufactured on the basis of NC-EEG nanocomposites as a positive electrode and activated carbon (AC) as a negative electrode, exhibited a maximum energy density of 86Whkg−1 and a maximum power density of 16.5kWkg−1. It is believed that our 3D nano-architectured composites with excellent electrochemical performances would be promising candidates for supercapacitor materials.

N and P co-functionalized three-dimensional porous carbon networks as efficient metal-free electrocatalysts for oxygen reduction reaction

Developing low-cost and high-performance metal-free oxygen reduction reaction (ORR) catalysts for fuel cells is highly desirable but still full of challenges. In this study, nitrogen and phosphorus co-functionalized three-dimensional (3D) porous carbon networks (NPCN) have been prepared by pyrolysis the zero-dimensional carbon quantum dots (CQDs) and a supermolecular gel of self-assembled melamine and amino trimethylene phosphonic acid (ATMP). The resultant NPCN catalysts possess unique 3D networks-like porous architecture, large specific surface area (743 m2 g−1) and abundant edge defects. As a catalyst for ORR, the optimized NPCN-900 (pyrolyzed at 900 °C) displays positive onset potential at 0.92 V and 0.74 V (vs. RHE) in alkaline and acidic media respectively, which are roughly close to those of Pt/C (0.93 V and 0.80 V). Additionally, the NPCN-900 exhibits longer-term stability and strong endurance to methanol over a wide pH range of aqueous media, which is much superior to that of Pt/C. Considering the outstanding activity of NPCN-900, it can be worked as a prospective metal-free catalyst to substitute commercial Pt/C for ORR in fuel cells.

Nanoporous Mo 2 C functionalized 3D carbon architecture anode for boosting flavins mediated interfacial bioelectrocatalysis in microbial fuel cells

Abstract An efficient microbial electrocatalysis in microbial fuel cells (MFCs) needs both high loading of microbes (biocatalysts) and robust interfacial electron transfer from microbes to electrode. Herein a nanoporous molybdenum carbide (Mo2C) functionalized carbon felt electrode with rich 3D hierarchical porous architecture is applied as MFC anode to achieve superior electrocatalytic performance. The nanoporous Mo2C functionalized anode exhibits strikingly improved microbial electrocatalysis in MFCs with 5-fold higher power density and long-term stability of electricity production. The great enhancement is attributed to the introduction of rough Mo2C nanostructural interface into macroporous carbon architecture for promoting microbial growth with great excretion of endogenous electron shuttles (flavins) and rich available nanopores for enlarging electrochemically active surface area. Importantly, the nanoporous Mo2C functionalized anode is revealed for the first time to have unique electrocatalytic activity towards redox reaction of flavins with more negative redox potential, indicating a more favourable thermodynamic driving force for anodic electron transfer. This work not only provides a promising electrode for high performance MFCs but also brings up a new insight into the effect of nanostructured materials on interfacial bioelectrocatalysis.

Kirkendall Effect in Creating Three-Dimensional Metal Catalysts for Hierarchically Porous Ultrathin Graphite with Unique Properties

In this work, we report an innovative mechanism, the Kirkendall effect, in creating three-dimensional (3D) microporous catalysts with tunable pore sizes for the growth of hierarchic ultrathin graphite foams (HP-UGFs) with unique properties. Employing the Kirkendall effect is one of the first demonstrated for fabricating 3D porous catalysts, where tunable pores of 1.9–8.3 μm are created on 3D interconnected struts (∼100 μm). With the catalysts, we readily synthesized freestanding HP-UGFs that offer higher crystallinity and electric conductivity, larger surface area, as well as enhanced electric invariance to strains compared to those of conventional ultrathin graphite foams. A gauge factor as low as ∼10 at a strain as high as 80% is achieved owing to the unique porous corrugations created on the microstruts of the HP-UGFs. This work may inspire a new paradigm in designing and synthesizing a new type of 3D porous architecture made of 2D materials with controlled local corrugations, which could greatly benef...

High-Capacity and Ultrafast Na-Ion Storage of a Self-Supported 3D Porous Antimony Persulfide-Graphene Foam Architecture.

The key challenge for high-performance sodium-ion batteries is the exploitation of appropriate electrode materials with a long cycling stability and high rate capability. Here, we report Sb2S5 nanoparticles (∼5 nm) uniformly encapsulated in three-dimensional (3D) porous graphene foam, which were fabricated by a facile hydrothermal coassembly strategy, as a high-performance anode material for sodium-ion batteries. The as-prepared composite can be directly used as electrodes without adding a binder or current collector, exhibiting outstanding electrochemical performance with a high reversible capacity (845 mA h g-1 at 0.1 A g-1), ultralong cycling life (91.6% capacity retention after 300 cycles at 0.2 A g-1), and exceptional rate capability (525 mA h g-1 at 10.0 A g-1). This is attributed to fast Na+ ion diffusion from the ultrasmall nanoparticles and excellent electric transport between the active material and 3D porous graphene, which also provide an effective strategy for anchoring the nanoparticles. Experimental results show that the Sb2S5 undergoes a reversible reaction of Sb2S5 + 16Na ↔ 5Na2S + 2Na3Sb during sodiation/desodiation. Moreover, a full cell with Na3(VO0.5)2(PO4)2F2/C cathode and the as-prepared composite anode was assembled, displaying high output voltage (∼2.2 V) with a stable capacity of 828 mA h g-1 for anode material (with 100 cycles at 0.1 A g-1), showing the potential for practical application.

RETRACTED ARTICLE: Self-assembly of N doped 3D porous carbon frameworks from carbon quantum dots and its application for oxygen reduction reaction

Developing low-cost and high-performance metal-free oxygen reduction reaction (ORR) catalysts for fuel cells is highly desirable but still full of challenges. In this study, Nitrogen-doped three-dimensional (3D) porous carbon frameworks (NCF) derived from zero-dimensional carbon quantum dots have been prepared by a simple one-step self-assembly technique. The resultant NCF-800 (carbonized at 800 °C) possesses unique 3D porous framework architecture, large specific surface area (171 cm2 g−1) and abundant defect sites. As a catalyst for ORR, the optimized NCF-800 displays a positive onset potential at 0.87 V (vs. RHE), which is roughly 60 mV more negative than that of Pt/C (0.93 V). Additionally, the NCF-800 exhibits longer-term stability and strong endurance to methanol in alkaline electrolyte, which are much superior to those of Pt/C. Considering the outstanding activity of NCF-800, it can be worked as a prospective metal-free ORR catalyst for fuel cells in the future.

Facile fabrication of 3D porous hybrid sphere by co-immobilization of multi-enzyme directly from cell lysates as an efficient and recyclable biocatalyst for asymmetric reduction with coenzyme regeneration in situ

Ni2+-agarose bead-wrapped multi-enzyme/inorganic hybrid sphere composed of the immobilized enzymes as organic component and NaH2PO4 and NaCl as inorganic component was developed by co-immobilizing extracellular His-tagged 3-quinuclidinone reductases and glucose dehydrogenase without pre-purification. The resulting biocatalysts has 3D porous architectures as confirmed by SEM and FESEM, and it enabled the continuous biotransformation of 3-quinuclidone to (R)-3-quinuclidinol with cofactor regeneration in situ. The 3D porous biocatalysts were formed via three steps: First, immobilization of the His-tagged enzymes directly from the cell lysates supernatant. Next, formation of enzyme aggregates, ribbons and gels. Finally, the enzymes, the formed aggregates/ribbons/gels and salt were incorporated to the foam and then covered the Ni2+-agarose bead. The technique made the immobilization of these enzymes effective such that specific enzyme loading of 60.8mg/g support and enzyme loading efficiency of 92.3% were achieved. As a direct consequence, the biocatalyst catalyzed the conversion of 3-quinuclidinone (204g/L) to (R)-3-quinuclidinol in 100% yield and 100% ee at 4.5h, and the recyclability of the biocatalyst was excellent, retaining>95% conversion yield and 100% ee even after the fifteenth runs. Overall, our strategy is demonstrated to be a promising method for developing efficient and robust biocatalyst for asymmetric synthesis.

Preparation of Three-Dimensional Co3O4/graphene Composite for High-Performance Supercapacitors

Here, we developed a simple and efficient route for the preparation of three-dimensional (3D) Co3O4-anchored graphene composites using the sacrificial template-assisted method and the subsequent deposition process of Co3O4 nanoparticles. As structural guiding materials, polystyrene (PS) spheres provide 3D porous architectures with a high surface area. 3D porous graphene materials serve as conductive supporters for the deposition of Co3O4 nanoparticles through precipitation growth. The 3D porous composite structures of Co3O4/graphene composites were intensively investigated using scanning electron microscope, transmission electron microscope, and X-ray diffraction. The 3D Co3O4/graphene composites show a high specific capacitance of 328 F g−1 with efficient and fast charge–discharge process in aqueous 6 M KOH electrolyte. In addition, the composites provide a good cycle lifetime, which retained 98% capacitance retention over 2000 cycles.

Fabrication and evaluation of thermosensitive chitosan/collagen/α, β-glycerophosphate hydrogels for tissue regeneration

Thermosensitive hydrogels whose physiological properties are similar to extracellular matrix have been extensively used for tissue regeneration. Polysaccharides and proteins, as biocompatible substrates similar to bio-macromolecules that could be recognized by human body, are two preferred polymers for fabrication of such hydrogels. A series of novel thermosensitive hydrogels (CS-ASC-HGs) containing chitosan (CS) and acid-soluble collagen (ASC) were thus prepared, in the presence of α, β-glycerophosphate, to mimic extracellular microenvironment for tissue regeneration. Rheological measurements demonstrated excellent thermosensitivity. FT-IR and SEM indicated CS-ASC-HGs possessed 3D porous architectures with fibrous ASC, and the molecular structure of ASC was well-maintained in hydrogels. Hemolysis, acute toxicity, and cytotoxicity tests suggested CS-ASC-HGs were of good biocompatibility. CS-ASC-HGs were able to support the survival and proliferation of L929 cells encapsulated in them. Moreover, CS-ASC-HGs had better pH stability and biocompatibility than pure CS hydrogel. These results suggested that CS-ASC-HGs could serve as promising scaffolds for tissue regeneration.

A Highly Active CoFe Layered Double Hydroxide for Water Splitting

Highly active, cost-effective, and durable catalysts for oxygen evolution reaction (OER) are required in energy conversion and storage processes. A facile synthesis of CoFe layered double hydroxide (CoFe LDH) is reported as a highly active and stable oxygen evolution catalyst. By varying the concentration of the metal ion precursor, the Co/Fe ratios of LDH products can be tuned from 0.5 to 7.4. The structure and electrocatalytic activity of the obtained catalysts were found to show a strong dependence on the Co/Fe ratios. The Co2 Fe1 LDH sample exhibited the best electrocatalytic performance for OER with an onset potential of 1.52 V (vs. the reversible hydrogen electrode, RHE) and a Tafel slope of 83 mV dec-1 . The Co2 Fe1 LDH was further loaded onto a Ni foam (NF) substrate to form a 3D porous architecture electrode, offering a long-term current density of 100 mA cm-2 at 1.65 V (vs. RHE) towards the OER.

Three-dimensional porous graphene-encapsulated CNT@SnO2 composite for high-performance lithium and sodium storage

Tin oxide (SnO2) is regarded as a promising anode material for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to its large theoretical capacity. However, poor electrical conductivity and the weak cyclability resulted from dramatic volume expansion upon cycling process still hinder its practical application. Herein, we report a facile two-step hydrothermal route to encapsulate core–shell structured carbon nanotube (CNT)@SnO2 composite in a graphene coating with novel three-dimensional (3D) porous framework architecture (CNT@SnO2@G) as anode for both LIBs and SIBs. The resultant CNT@SnO2@G electrode suggests outstanding lithium and sodium storage performance with large specific capacity, remarkable cycling stability and excellent rate capability. For LIBs, it delivers a high initial discharge capacity of 1400mAhg−1 at 100mAg−1, improved reversible capacity of 947mAhg−1 after 100 cycles at 100mAg−1, and enhanced rate capability of 281mAhg−1 at 3000mAg−1. In addition, sodium storage testing suggests that a high discharge capacity of 323mAhg−1 after 100 cycles at 25mAg−1 was achieved. The present unique structural design associated with the remarkable lithium and sodium storage performance ensures CNT@SnO2@G as an advanced anode material for rechargeable LIBs and SIBs.

A facile synthetic strategy to three-dimensional porous ZnCo2O4 thin films on Ni foams for high-performance lithium-ion battery anodes

Three-dimensional (3D) porous ZnCo2O4 thin films on nickel foam substrates have been fabricated through a facile strategy of electrostatic spray deposition (ESD) followed by annealing in Ar atmosphere for lithium-ion battery anodes. The obtained ZnCo2O4 films on Ni foams show excellent cycling performance with a reversible capacity of over 1726mAhg−1 after 100cycles at 400mAg−1. The ZnCo2O4 electrodes also present good rate capability with 811mAhg−1 at 5Ag−1. The improved electrochemical performances should be ascribed to 3D porous ZnCo2O4 architecture directly grown on Ni foam current collector, due to the synergistic advantages of offering more reaction sites, effective void space to the volume variation during cycling, and improving of electron transport. It is proposed that this facile strategy of ESD technique can be extended to synthesize other 3D porous mixed transition-metal oxide materials.

An Electrochemical Sensor Based on Graphene-Polypyrrole Nanocomposite for the Specific Detection of Pb (II)

An electrochemical sensor for the rapid, selective and sensitive detection of Pb[Formula: see text] was developed using polypyrrole-graphene (PPY-rGO) nanocomposite by electrochemical synthesis. The PPY-rGO-modified electrode possessed a large effective area because of unique 3D porous architectures, and it displayed excellent selectivity for the determination of Pb[Formula: see text]. The response of Pb[Formula: see text] on the nanocomposite-modified electrode was evaluated, and the relevant parameters were optimized by square wave anodic stripping voltammetry (SWASV). The stripping response was highly linear ([Formula: see text]) over a Pb[Formula: see text] concentration range of [Formula: see text][Formula: see text]mol/L to [Formula: see text][Formula: see text]mol/L, with a detection limit of [Formula: see text][Formula: see text]mol/L (3[Formula: see text] method). Furthermore, its applicability was validated for the determination of Pb[Formula: see text] levels using spiked tap water at different concentrations. The polyporous structure, satisfactory reproducibility, long-term stability and simple synthesis endow the PPY-rGO nanocomposite a promising application in the determination of Pb[Formula: see text].

Understanding the effects of 3D porous architectures on promoting lithium or sodium intercalation in iodine/C cathodes synthesized via a biochemistry-enabled strategy.

Rechargeable sodium-iodine and lithium-iodine batteries have been demonstrated to be promising and scalable energy-storage devices, but their development has been seriously limited by challenges such as their inferior stability and the poor kinetics of iodine. Anchoring iodine to 3D porous carbon is an effective strategy to overcome these defects; however, both the external architecture and internal microstructure of the 3D porous carbon host can greatly affect the ion intercalation of iodine/C electrodes. To realize the full potential of iodine electrodes, a biochemistry-enabled route was developed to enable the controllable design of different 3D porous architectures, from hollow microspheres to 3D foam, for use in iodine/C cathodes. Two types of spores with spherical cells, i.e. Cibotium Barometz (C. Barometz) and Oetes Sinesis (O. Sinesis), are employed as bio-precursors. By carefully controlling the degree of damage on the bio-precursors, different targeted carbon hosts were fabricated. Systematic studies were carried out to clarify the structural effects on modifying the ion-intercalation capabilities of the iodine/C cathodes in lithium-iodine and sodium-iodine batteries. Our results demonstrate the profound performance improvements of both 3D bio-foam and hollow sphere because their hierarchically porous structures can strongly immobilize iodine. Notably, the 3D bio-foam based iodine composites achieve faster ion kinetics and enhanced rate capability than their hollow sphere based counterparts. This was attributed to their higher micro/mesopore volume, larger surface area and improved packing density, which result in the highly efficient adsorption of iodine species. By virtue of the thinnest slices, the iodine/bio-foam derived from C. Barometz spores achieves the best high-rate long-term cycling capability, which retains 94% and 91% of their capacities in lithium-iodine and sodium-iodine batteries after 500 cycles, respectively. With the help of the biochemistry-assisted technique, our study provides a much-needed fundamental insight for the rational design of 3D porous iodine/C composites, which will promote a significant research direction for the practical application of lithium/sodium-iodine batteries.

Hierarchical micro-lamella-structured 3D porous copper current collector coated with tin for advanced lithium-ion batteries

A Novel 3D porous Sn-Cu architecture is prepared as an anode material for use in an advanced lithium-ion battery. Micro-lamellar-structured 3D porous Cu foam, which is electroless-plated with Sn as an active material, is used as anode current collector. Compared to Sn-coated Cu foil, the 3D Sn-Cu foam exhibits superior Li-ion capacity and stable capacity retention, demonstrating the advantage of 3D porous architecture by preserving its structural integrity. In addition, the effect of heat-treatment after Sn plating is investigated. Sn/Sn6Cu5 and SnO2/Cu10Sn3 were formed on and in the 3D Sn-Cu foam under the heat-treatment at 150°C and 500°C, respectively. The development of Cu10Sn3 in the 3D Sn-Cu foam heat-treated at 500°C can be a key factor for the enhanced cyclic stability because the Cu10Sn3 inactively reacts with Li-ion and alleviates the volume expansion of SnO2 as an inactive matrix.

Graphene intercalated in graphene-like MoS 2 : A promising cathode for rechargeable Mg batteries

Abstract In this paper, we report the synthesis of graphene-like MoS2/graphene hybrid by a facile lithium-assisted sonication method and its cathode application for rechargeable Mg batteries. Instrumental analyses elucidate that the composite displays a three-dimensional (3D) porous architecture constructed by exfoliated single or few MoS2 layers, and some graphene is intercalated in the MoS2 gallery with an enlarged interlayer spacing from 0.62 to 0.98 nm. The obtained MoS2/graphene hybrid exhibits high electrochemical performance with a remarkable capacity (115.9 mA h g−1) and good cyclic stability (82.5 mA h g−1 after 50 cycles). This is owing to the synergistic effect between the graphene-like MoS2 and the highly conductive graphene, which can effectively facilitate the Mg2+ ions diffusion and electrons transfer, provide abundant active sites for Mg2+ intercalation, and prevent structural collapse upon prolonged cycling.

The hybrid nanostructure of vertically aligned cobalt sulfide nanoneedles on three-dimensional graphene decorated nickel foam for high performance methanol oxidation

In this report, vertically aligned one-dimensional (1D) cobalt sulfide nanoneedles (CS-NNs) were directly synthesized onto the three-dimensional graphene (3DG) as the CS-NNs/3DG hybrid nanostructure and applied to methanol oxidation reaction (MOR). The 3DG and CS-NNs were prepared by chemical vapor deposition and two-step hydrothermal method, respectively. The 1D cobalt carbonate hydroxide nanoneedles (CCH-NNs) were initially synthesized onto the graphene surface of 3DG via the hydrothermal method (Step I). Finally, the CCH-NNs were converted into CS-NNs via the hydrothermal treatment using Na2S as the sulfur source with the help of the Kirkendall effect (Step II). The structures and morphologies of 3DG, CCH-NNs/3DG, and CS-NNs/3DG were investigated by Raman spectroscopy, scanning electron microscopy and X-ray diffraction. The electrocatalytic performance was investigated by cyclic voltammetry measurements. The CS-NNs/3DG electrode showed higher electrocatalytic activity for MOR compared with CCH-NNs/3DG and 3DG. The excellent electrocatalytic performances of 3DG supported CS-NNs come from the unique 3D porous architecture, which can provide sufficient open spaces and shorter ion diffusion paths to facilitate rapid ionic transportation. Direct synthesis of 1D CS-NNs on graphene can result in a low resistance for fast electron transfer. The vertically aligned binder-free 1D CS-NNs not only avoid the aggregation to enhance the utilization efficiency of catalytic active sites but also serve as an electron highway in the axial direction for electron collection. The prepared CS-NNs/3DG is a promising non-platinum electrocatalyst for direct methanol fuel cells.

Reconstruction of copper shell on metal oxides as enhanced nanoarrays electrodes for lithium ion batteries

Transition metal oxides anodes of lithium ion batteries (LIBs) usually suffer from low reaction kinetics with slow charge/ions transfer resulting from severe volume variation. In this work, thin porous copper shell is homogeneously coated on the CoO nanowires forming CoO/Cu hetero-structured arrays. Cu shell not only acts as a conductive network, but also serves as a protective “armor” layer to keep electrode stable upon cycling. Meanwhile, 3D porous architecture with large surface area is well preserved in the CoO/Cu hetero-structured arrays. Due to enhanced electron/ion transfer characteristics and strengthened electrode structure, the as-prepared CoO/Cu hetero-structured arrays exhibit much higher electrochemical reactivity with lower polarization and better reversibility due to the introduction of thin Cu shell. Additionally, enhanced discharge capacity and large-rate performances are also demonstrated in the CoO/Cu hetero-structure arrays when compared with the pure CoO nanowires counterpart.