Three-dimensional Carbon Matrix Research Articles

Molten salt-assisted synthesis of carbon polyhedra with self-grown carbon nanotubes on the surface for boosting peroxymonosulfate activation

Despite attempts made to use carbon nanotubes (CNTs) as metal-free catalysts for peroxymonosulfate (PMS) activation recently, the challenge remains in the preparation of carbon nanotubes by an in-situ method. In this paper, basing a novel molten salt-assisted method with heat treatment, cobalt (Co) and nitrogen (N) co-doped carbonaceous polyhedrons with self-catalyzed-grown CNTs on the surface (CNT@CoNC-x) were synthesized and employed to activate PMS to degradation oxytetracycline (OTC) in the aqueous phase. Such a unique structure, the three-dimensional carbon matrix with Co and N co-doped in the CNT@CoNC-x, not only confirmed the control of the active sites by the simple method, but also promoted the interaction between metal nanoparticles and CNTs. It is beneficial to accelerate the decomposition of PMS, which in turn improves the degradation efficiency of OTC. A two-stage kinetics of OTC degradation was studied and the apparent rate constant (k0∼5min) of the CNT@CoNC-5 catalyst is 66.97 L/g min−1, which increased 25.46 times greater than that of the CoNC catalyst obtained by calcining ZIF-67 directly. CNT@CoNC-5 catalysts exhibited good environmental resistance and recyclability.

Me-N-C Electrocatalysts for Electrochemical CO2 Reduction to High-Value Products

The development of sustainable carbon-neutral energy technologies to mitigate greenhouse gas emissions has become imperative and urgent. Of special interest and importance in this context is the use of electricity from intermittent renewable energy sources (wind, solar) for electrochemical conversion of carbon dioxide (CO2) to easily storable and transportable value-added products: fuels and feedstock chemicals. Nanoparticles of non-precious metals, e.g., Cu, Sn, Co, show high activity for electrochemical CO2 reduction reaction (CO2RR) but suffer from poor selectivity, resulting in a mixture of products that require tedious and costly separation. Recently, transition metal- and nitrogen-doped carbon (Me-N-C) materials have been emerged as promising CO2RR catalysts thanks to their well-defined structures and good activity. However, their selectivity, while respectable for the generation of carbon monoxide (CO), is low for high energy-content products. A limited understanding of reaction pathways and degradation mechanism of Me-N-C catalysts for CO2RR has additionally stemmed a rational design of these materials.In this presentation, we summarize our study of the activity, selectivity, and stability of Me-N-C (Me = Fe, Co, Ni, or Cu, etc.) catalysts for the CO2RR, focusing on the role of the local coordination environment at metal centers and metal-carbon substrate interactions. We also report the obtained bimetallic M1M2-N-C catalysts, designed to enable the formation of multi-carbon products through CO2RR and utilizing high surface-area three-dimensional carbon matrix as support for metal sites with improved CO2RR activity. The main objective of this work is to use Me-N-C catalysts to produce high energy-density chemicals, enhance mechanistic understanding, and bring CO2RR closer to practical applications.

Recovering copper ions from wastewater with chitosan to synthesize lead-free primary explosives

Chitosan (CTS) is a well-known adsorbent capable of absorbing copper ions. It's also a high-quality biomass carbon source. The carbon skeleton formed by the pyrolysis of CTS has outstanding electrical conductivity, which can help copper azide (CA), a new type of primary explosive that's particularly sensitive to electrostatic stimuli, be more electrostatically safe. The CTS-Cu complex is precipitated by using CTS to adsorb and flocculate copper ions in wastewater. To construct the Cu@carbonized chitosan (CCTS) precursor material, the organic ligands in the CTS-Cu complex are calcined into a porous three-dimensional carbon matrix, and the copper ions are transformed into copper nanoparticles embedded in CCTS. The azide reaction converts copper nanoparticles (CuNPs) into high-energy CA. With its good electrical conductivity, CCTS maintains its framework structure and effectively improves the electrostatic safety of composite energetic materials. CA@CCTS has a CA content of 69.7%, an electrostatic ignition energy (E 50 ) of about 1.19 mJ, and a heat release of 1803.22 J/g. This work takes advantage of CA and CTS's environmental friendliness. CA@CCTS, as a novel lead-free primary explosive, has good electrostatic safety while containing a high proportion of CA. • The CTS-Cu complex is precipitated by using CTS to adsorb and flocculate copper ions in wastewater. • The Cu@CCTS precursor is constructed by carbonizing the CTS-Cu complex. • The Cu@CCTS precursor is converted to CA@CCTS via a gas-solid phase azide reaction. • CA@CCTS has a CA content of 69.7%, an 50% electrostatic ignition energy (E 50 ) of about 1.19 mJ.

Boosting the Rate Performance of Li–S Batteries via Highly Dispersed Cobalt Nanoparticles Embedded into Nitrogen-Doped Hierarchical Porous Carbon

Boosting the Rate Performance of Li–S Batteries via Highly Dispersed Cobalt Nanoparticles Embedded into Nitrogen-Doped Hierarchical Porous Carbon

In-situ synthesis of manganese oxide‑carbon nanocomposite and its application in activating persulfate for bisphenol F degradation

In this work, manganese oxide‑carbon nanocomposite catalytic materials (MnO@CNs) with a “core-shell” structure were synthesized in the one-step synthesis using sodium alginate as a template. XRD and Raman spectroscopy proved that high calcination temperatures were beneficial to the graphitization of carbon and the formation of Mn7C3. Both SEM and TEM images of MnO@CNs identified that MnO nanoparticles were encapsulated in a three-dimensional carbon matrix and simultaneously protected by a “carbon-shell” with an adherent graphite structure, which could facilitate electron transfer. The MnO@CNs could activate PS to degrade BPF completely within 30 min in solutions with a wide pH range or coexisting anions and organics. The valence change of Mn could promote the generation and conversion of various free radicals and non-radicals, of which O2·− played a leading role in the decomposition of BPF. In addition, the potential degradation pathways and degradation mechanisms of BPF in the MnO@CNs/PS system were also explored according to DFT calculations and product detection results.

Engineering of Coordination Environment and Multiscale Structure in Single-Site Copper Catalyst for Superior Electrocatalytic Oxygen Reduction.

Herein, we report efficient single copper atom catalysts that consist of dense atomic Cu sites dispersed on a three-dimensional carbon matrix with highly enhanced mesoporous structures and improved active site accessibility (Cu-SA/NC(meso)). The ratio of +1 to +2 oxidation state of the Cu sites in the Cu-SA/NC(meso) catalysts can be controlled by varying the urea content in the adsorption precursor, and the activity for ORR increases with the addition of Cu1+ sites. The optimal Cu1+-SA/NC(meso)-7 catalyst with highly accessible Cu1+ sites exhibits superior ORR activity in alkaline media with a half-wave potential (E1/2) of 0.898 V vs RHE, significantly exceeding the commercial Pt/C, along with high durability and enhanced methanol tolerance. Control experiments and theoretical calculations demonstrate that the superior ORR catalytic performance of Cu1+-SA/NC(meso)-7 catalyst is attributed to the atomically dispersed Cu1+ sites in catalyzing the reaction and the advantage of the introduced mesoporous structure in enhancing the mass transport.

One-step construction of three-dimensional nickel sulfide-embedded carbon matrix for sodium-ion batteries and hybrid capacitors

A three-dimensional design composing of porous carbon matrix (PCM) decorated with nickel sulfide nanoparticles (denoted as NiSx@PCM) was fabricated through a one-step hydrothermal process, and successfully utilized as an electrode material in high performance sodium-ion batteries (SIBs) and sodium-ion hybrid capacitors (SIHCs). The as-prepared NiSx@PCM delivered a high reversible capacity of 650 mAh g−1 over 200 cycles at 0.5 A g−1, outstanding rate capability (167 mAh g−1 at as high as 20 A g−1), and excellent cycle performance (300 mAh g−1 at 1 A g−1 after 800 cycles) in the SIBs. In addition, SIHCs based on NiSx@PCM composite anodes and commercial activated-carbon cathodes behaved carried remarkably high energy densities of 99.3 and 52.2 Wh kg−1 at power densities of 140 and 4480 W kg−1, respectively. The significantly high-performance enhancement should be attributed to the excellent electron/ion transports within the three-dimensional active material-carbon network during charging/discharging with the in-situ growth of the more conductive nickel sulfide nanoparticles throughout the porous carbon matrix. This work presents a facile method to synthesize three-dimensional carbon matrix incorporating metal sulfide nanoparticles, as well as suggests new insights into further advancing next-generation high energy-density/power-density energy storage units by combining the merits of both batteries and supercapacitors.

Selective synthesis of CuO/C nanocomposites and porous CuO based on polyacrylic acid hydrogel system as high-performance anode for lithium-ion batteries

CuO/C nanocomposites and porous CuO were selectively synthesized by a facile, low-cost and large-scale synthesis method based on polyacrylic acid hydrogel system. As the anode materials for lithium-ion batteries, the capacity of porous CuO is higher than CuO/C nanocomposites, while gradually decreases after 40 cycles due to the lack of supporting matrix. In CuO/C nanocomposites, CuO nanoparticles are uniformly embedded in the three-dimensional carbon matrix, which can buffer the large volume change, suppress the particle pulverization, and prevent the particle agglomeration of CuO nanoparticles. The capacity of CuO/C nanocomposites maintains at about 690 mAh g−1 till 200th cycle.

Facile preparation of robust porous MoS2/C nanosheet networks as anode material for sodium ion batteries

Developing advanced MoS2 anode material for sodium ion battery is still a big challenge since it is hindered by poor cycling stability and rate capability owing to huge volume variation during charge/discharge processes and low conductivity. In this work, three-dimensional porous networks consisting of several-layered MoS2/C nanosheets are synthesized via a facile freeze-drying approach using NaCl as template. MoS2/C nanosheet networks demonstrate a high reversible capacity of 389 mAh g−1 and maintain 370 mAh g−1 after 100 cycles at 100 mA g−1, indicating excellent cycling stability. Good rate properties are also achieved with reversible capacities of 292, 256, 223, 174 mAh g−1 at 1, 2, 4, 6 A g−1, respectively. The excellent electrochemical performance can be ascribed to the unique three-dimensional networks consisting of few-layered MoS2 nanosheets, which facilitates sodium ion diffusion via near-surface reaction. Moreover, the robust three-dimensional carbon matrix can not only provide a conductive network, but also buffer the strain and maintain the electrode integrity during repeated sodiation/desodiation process. This strategy presents a new path for fabricating low-cost and high-yield three-dimensional metal sulfide (phosphide)/carbon composites for applications in energy-related fields and beyond.

All-solid-state lithium–sulfur batteries with three-dimensional mesoporous electrode structures

Abstract Although the characteristics of lithium–sulfur batteries are advantageous for various applications, batteries with liquid electrolytes show capacity fading due to the dissolution of polysulfides. All-solid-state lithium–sulfur batteries with highly reversible characteristics are developed using a three-dimensional carbon matrix framework structure for the sulfur cathode. Sulfur is introduced into a carbon replica framework with a pore size of 8–100 nm. The composite electrode structure provides high electronic conduction and allows high cathode utilization during the battery reaction. The capacity of cells using a LiAl alloy as the negative electrode and the thio-LISICON (lithium superionic conductor) electrolyte increases when the pore size of the carbon replica is decreased from 100 nm to less than 15 nm. The highest capacity is obtained for the carbon replica with a pore size of 8.6 nm and a wall thickness of 4.7 nm. An examination of the relationship between the charge–discharge capacity and the structure of carbon replicas with different pore sizes and wall thicknesses indicates that three-dimensional highly ordered mesoporous carbon with a small pore size is a promising electrode structure for lithium–sulfur all-solid-state batteries.

Facile synthesis of ultrafine SnO2 nanoparticles embedded in carbon networks as a high-performance anode for lithium-ion batteries

Abstract SnO 2 @C nanocomposites are easily synthesized in a large scale by the hydrolysis of Sn 4+ ions in a polyacrylic acid (PAA) hydrogel system, followed by the decomposition of Sn(OH) 4 and carbonization of PAA by heat treatment in one-system. The SnO 2 @C nanocomposites contain uniform ultrafine SnO 2 nanoparticles (≈4.3 nm) homogenously embedded in a three-dimensional carbon matrix. This unique structure efficiently suppresses the particle pulverization and aggregation of SnO 2 , thus maintaining the electrode integrity during long-term lithiation/delithiation process. The discharge capacity of SnO 2 @C nanocomposites is maintained at ∼597.3 mAh g −1 after 220 cycles. This scalable approach has great potential in the applications of high-capacity anodes in Li-ion batteries.

Highly active nonprecious metal hydrogen evolution electrocatalyst: ultrafine molybdenum carbide nanoparticles embedded into a 3D nitrogen-implanted carbon matrix

The generation of clean and sustainable hydrogen fuel through water splitting demands efficient and robust earth-abundant catalysts for the hydrogen evolution reaction (HER). A new hybrid, which was fabricated by incorporating molybdenum carbide (MoxC) nanoparticles into a nitrogen-implanted three-dimensional carbon matrix (MoCN-3D), was developed as a highly active and durable nonprecious metal electrocatalyst for HER. The porous architecture of MoCN-3D can provide continuous mass transportation with a minimal diffusion resistance and thus produce effective electrocatalytic kinetics in both acidic and alkaline media. Experimental observations in combination with density functional theory calculations reveal that the effective coupling between molybdenum carbide nanoparticles and the carbon matrix, as well as N hybrid coordination, can modify the electronic Fermi level of the final hybrid, which synergistically reduces the proton adsorption and the reduction barrier during electrocatalytic HER. A three-dimensional, porous catalytic framework makes it easier to flow water past active sites that turn this molecule into hydrogen. The hunt for cheaper alternatives to platinum catalysts for water splitting led Jinhua Ye from Tianjin University in China and co-workers to investigate molybdenum carbide (Mo2C). These catalysts show significant hydrogen evolution when confined to nanoscale shapes. The researchers enhanced this behaviour by replacing imidazole-zinc units in a zeolite-type metal organic framework with molybdenum. Heating at high temperature turned the sieve-like template into a new composite containing ultrafine Mo2C nanoparticles and a three-dimensional matrix of graphitic carbon implanted with nitrogen atoms. The physical structure of this material improves mass transport of reagents to and from catalytic surface sites, while favorable interactions between Mo2C and the carbon matrix lower energy barriers needed to slice water apart. A new hybrid, fabricated by incorporating molybdenum carbide (Mo2C) nanoparticles into nitrogen-implanted three-dimensional carbon matrix (MoCN-3D), has been developed as a highly active and durable nonprecious metal electrocatalyst for HER. The porous architecture of the developed catalyst MoCN-3D can provide continuous mass transportation with a minimal diffusion resistance and thus produce effective electrocatalytic kinetics in both acidic and alkaline media.