New Carbon Materials最新文献

The modification and optimization of porous carbon electrodes is key to achieving high-performance supercapacitors. Oxygen-rich porous carbon nanosheets (OPCNs) with a two-dimensional (2D) structure produced from the solid by-products of the coal industry were prepared by taking advantage of the rigid confinement of 2D MgAl-layered double hydroxides (MgAl-LDH) combined with KOH activation. The influence of carbonization temperature on the microstructure and surface properties of the OPCNs was investigated. The surface morphologies/compositions and surface textures of the prepared OPCNs were observed and analyzed by SEM, TEM, N2 adsorption and desorption, elemental analysis, etc. The optimized carbon sample activated at 700 °C (OPCN-700) had a high oxygen content of 24.4 wt%, a large specific surface area of 2 388 m2 g−1, and good wettability. In addition, the abundant micropores and 2D nanosheet structure of OPCN-700 provide efficient storage and transport for electrolyte ions. Because of this, when used as the electrode for a supercapacitor it has a high specific capacitance of 382 F g−1 at 0.5 A g−1, an excellent rate performance and cycling stability.

Raman mapping microspectroscopy was then used to investigate the interfacial stress distributions of the films during different cryogenic-room temperature cycles (-198-25 °C, 0-300 cycles). It was found that the micro stress of CNT-PI films (around 175 MPa) had no significant changes even after 300 cycles. The cryogenic cycling had very little effect on the internal stress, indicating that PI had a good low temperature resistance. For the CF/CNT-PI films, the micro stress distributions of CFs, interface, and matrix regions were successfully obtained. It was found that the CFs bear a greater stress than the matrix, showing that CFs had always been the major stress bearer, confirming the strengthening effect of CFs. When the CF/CNT-PI films were cycled fewer than 250 times, the effect of cryogenic cycling on the micro stress was insignificant. But once the number of cycles reached 300, the compressive stresses on the fiber and interface increased by 21% and 12.9%, respectively, implying a deterioration of the mechanical properties. By Raman mapping, the micro-mechanical distributions of the reinforced material, matrix and interface of the composites under cyclic temperature changes were effectively quantified. This is therefore an effective method for evaluating the safety of composite materials.

An electrochemical sensor for Cu(II) based on ion-imprinted polymers was prepared by combining surface imprinting with electrochemical polymerization deposition. The sensor was modified by ion-imprinted magnetic carbon nanospheres with a specific selectivity and sensitivity for Cu(II). The morphology and structure of the materials were characterized and analyzed. Sensors with the imprinted electrode had a stronger selectivity and higher sensitivity towards Cu(II) compared with their original counterparts. Within relative concentrations of Cu(II) from 10⁻⁶ to 10⁻¹⁰ mol L⁻¹, the detection limit of the sensor was as low as 5.138×10⁻¹⁶ mol L⁻¹ (S/N=3). The sensor is resistant to interference, and has good reproducibility, and stability, making it excellent for the electrochemical detection of metal ions.

Two-dimensional (2D) carbon materials have attracted enormous attention, but the complicated synthesis methods, inhomogeneous structure and uncontrollable properties still limit their use. Here we report a universal protocol for fabricating a series of heteroatom-doped 2D porous polymers, including pyrrole and indole as nitrogen-dopant sources, and 3,4-ethoxylene dioxy thiophene as a sulfur-dopant source by a simple chemical crosslinking reaction. This bottom-up strategy allows for the large-scale synthesis of functionalized ultrathin carbon nanosheets with a high heteroatom doping content and abundant porosity. Consequently, the obtained N-doped carbon-rich nanosheets (NCNs) sample has a specific capacity of 573.4 mAh g⁻¹ at 5 A g⁻¹ as an anode for lithium-ion capacitors (LICs), and the optimized sample has a specific capacitance of 100.0 F g⁻¹ at 5 A g⁻¹ when used as a cathode for a LIC. A dual-carbon LIC device was also developed that had an energy density of 168.4 Wh kg⁻¹ at 400 W kg⁻¹, while maintaining outstanding cycling stability with a retention rate of 86.3% after 10 000 cycles. This approach has the potential to establish a way for the precise synthesis of substantial amounts of 2D functionalized carbon nanosheets with the desired structure and properties.

To solve the problem of electromagnetic radiation pollution, it is necessary to develop an economic and environmentally friendly way of producing efficient electromagnetic wave absorbing materials. Carbon-based materials have attracted much attention but finding suitable precursors and ways of producing defined pore structures are still challenges. This work reported a facile method to produce porous carbon by using coal liquefaction oil residue as carbon source. The produced porous skeletons should be attributed to the generated Na₂CO₃ templates and CO₂ gas during the thermal decomposition process of NaHCO₃ templates. It is found that changing the pore structure not only adjusts the impedance matching of the material but also increases the length of the electromagnetic wave transmission path and increases dielectric loss. With the combined effect of multiple electromagnetic loss mechanisms, the material has excellent electromagnetic wave absorption. Specifically, with a filler loading of only 10% and a thickness of 2.03 mm, the obtained carbon material has a reflection loss value of −60.28 dB and an effective absorption bandwidth of 5.36 GHz. This work provides a new approach to developing high-performance carbon-based electromagnetic wave absorbing materials and also offers a new idea for the high value-added use of coal liquefaction oil residue products.

Vertically aligned carbon nanotube (VACNT) arrays with good mechanical properties and high thermal conductivity can be used as effective thermal interface materials in thermal management. In order to take advantage of the high thermal conductivity along the axis of nanotubes, the quality and height of the arrays need to be optimized. However, the immense synthesis parameter space for VACNT arrays and the interdependence of structural features make it challenging to improve both their height and quality. We have developed a literature mining approach combined with machine learning and high-throughput design to efficiently optimize the height and quality of the arrays. To reveal the underlying relationship between VACNT structures and their key growth parameters, we used random forest regression (RFR) and SHapley Additive exPlanation (SHAP) methods to model a set of published sample data (864 samples). High-throughput experiments were designed to change 4 key parameters: growth temperature, growth time, catalyst composition, and concentration of the carbon source. It was found that a screened Fe/Gd/Al₂O₃ catalyst was able to grow VACNT arrays with millimeter-scale height and improved quality. Our results demonstrate that this approach can effectively deal with multi-parameter processes such as nanotube growth and improve control over their structures.

As the temperature of electronic devices continues to rise, the quest for high-efficiency heat dissipation has emerged as a critical concern, particularly when it comes to ensuring device performance and longevity. A high thermal conductivity is usually dependent on the ability of fillers to provide thermal conduction channels within composites. In recent years, the development of three-dimensional (3D) interconnected structures using high thermal conductivity fillers in composites has emerged as a promising approach. Compared to the traditional isotropic distribution and directional arrangements, 3D interconnected filler structures improve the thermal conductivity. We review research progress on metal matrix composites with a 3D interconnected carbon filler that have a high thermal conductivity. The thermal conductivity mechanisms and models of composites are elaborated, and important factors relevant to improving the thermal conductivity are considered. Ways of constructing 3D interconnected carbon networks and their effects on the thermal conductivity of their composites should serve as a reference for the advancement of high-performance metal matrix thermal conductivity composites.

Recently, solar-driven interfacial water evaporation (SDIWE) has attracted worldwide attention owing to its potential use in seawater desalination and wastewater purification. Nevertheless, how to effectively use the inevitable conduction heat loss and eliminate organic pollutants are still challenging. We report the SDIWE- assisted adsorption of organic pollutants by using the conduction heat loss to improve the total energy efficiency of the SDIWE system. Porous carbon (PC) and activated PC were prepared by a simple recrystallizing salt template-assisted carbonization and KOH activation method. After activation, the activated PC sample with a PC : KOH mass ratio of 1 : 4 (PC-A4) has a hierarchical porous structure, a better absorption capacity in the spectral region of 200-2500 nm, a high specific surface area of 1 867.71 m² g⁻¹ and a large pore volume of 1.04 cm³ g⁻¹. Based on this, PC-A4 has a high evaporation rate and energy efficiency, which can be further increased by regulating the mass of the water body. Subsequently, the conduction heat generated by the SDIWE system was used for SDIWE-assisted adsorption. Notably, the maximum amount of rhodamine B adsorbed by PC-A4 is 1 610 mg g⁻¹ at a conduction temperature of 309 K, which is higher than that of the same sample at 298 K. Consequently, this work offers a promising approach for effectively using the conduction heat loss of the SDIWE system and developing it for water purification.

Single-wall carbon nanotubes (SWCNTs) have been used to fabricate hydrogen gas (H₂) detectors for several decades. It has been proven that they barely interact with H₂ so that numerous modifications are used to assist this function. Additives include metals, metal oxides, polymers etc. Previous research suggests that the presence of functional groups on the SWCNTs may improve the response by several orders of magnitude. Recently, many different novel structures have been exploited, and structural parameters of the SWCNTs, such as diameter and chirality, also influence the performance of the detectors. Modifications of the SWCNTs are classified and other factors that influence the performance are also discussed, with the aim of accelerating the manufacture of detectors with a high responsivity and low limit of detection.

Capacitive deionization (CDI) is a potential cost-efficient desalination technology. Its performance is intrinsically limited by the structure and properties of the electrode materials. Biomass materials have become a research hotspot for CDI electrode materials because of their abundance, low cost, and unique structure. The preparation, desalination performance, and regeneration status of biochar electrodes are summarized and clarified. Their preparation and use in CDI in recent years are presented and compared, and the effects of biochar electrode materials and CDI operating parameters on the desalination performance are emphasized. It is found that the salt adsorption capacity is positively correlated with the percent mesoporous material they contain. The selective adsorption of ions mainly depends on ion properties like ionic radius and charge as well as voltage, charging time and feed water characteristics. The current status and methods of electrode regeneration are discussed and future developments are suggested.