Metal-organic frameworks-derived carbon modified wood carbon monoliths as three-dimensional self-supported electrodes with boosted electrochemical energy storage performance.

Wood-derived carbon monoliths, in recent years, have attracted tremendous interest in the field of energy storage, but their electrochemical characteristics are still far from satisfactory. Here, we report a universal and efficient approach for the preparation of structure-engineered, heteroatom-functionalized and property-boosted wood carbons. A two-step ion-exchange process greatly enriches the nucleation sites of ZIF-8 on the inner wall of wood tracheids, hence leading to a unique carbon/carbon heterostructure after carbonizing and acid-washing. Particularly, the prepared NPCM-900 with a large specific surface area of 708.2 m2 g-1, a hierarchical porous architecture and a suitable N content of 2.3% delivers an ultrahigh area-normalized specific capacitance of 23.7 F cm-2 at 5 mA cm-2, which stands for a new capacitive record among the wood-based binder-free electrodes. The NPCM-900//NPCM-900 all-solid-state supercapacitor has an admirable energy density of 9.3 Wh m-2 at 24.9 W m-2 and a large power density of 248.3 W m-2 at 4.8 Wh m-2, while the NPCM-900 based Zn-ion hybrid supercapacitor (NPCM-900//Zn) exhibits a superior energy density of 12.7 Wh m-2. Furthermore, the NPCM-900//NPCM-900 and NPCM-900//Zn present great stabilities with capacitance retentions of 87% and 85%, respectively, after 5000 cycles. These parameters notably outperform those of most wood-based supercapacitors, endowing the NPCM-900 with extensive prospects for practical use.

High Performance Tunable Catalysts Prepared by Using 3D Printing.

Honeycomb monoliths are the preferred supports in many industrial heterogeneous catalysis reactions, but current extrusion synthesis only allows obtaining parallel channels. Here, we demonstrate that 3D printing opens new design possibilities that outperform conventional catalysts. High performance carbon integral monoliths have been prepared with a complex network of interconnected channels and have been tested for carbon dioxide hydrogenation to methane after loading a Ni/CeO2 active phase. CO2 methanation rate is enhanced by 25% at 300 °C because the novel design forces turbulent flow into the channels network. The methodology and monoliths developed can be applied to other heterogeneous catalysis reactions, and open new synthesis options based on 3D printing to manufacture tailored heterogeneous catalysts.

Wiggling Mesopores Kinetically Amplify the Adsorptive Separation of Propylene/Propane.

Adsorptive separation is an appealing technology for propylene and propane separation; however, the challenge lies in the design of efficient adsorbents which can distinguish the two molecules having very similar properties. Here we report a kinetically amplified separation by creating wiggling mesopores in structurally robust carbon monoliths. The wiggling mesopores with alternating wide and narrow segments afford a surface area of 413 m2 g-1 and a tri-modal pore size distribution centered at 1.5, 4.2 and 6.6 nm, respectively. The synergistically kinetic and equilibrium effects were observed and quantitatively assessed, which together ensured a remarkable propylene/propane selectivity up to 39. This selectivity outperformed not only the available carbon adsorbents but also highly competitive among the dominated crystalline porous adsorbents. In addition, the wiggling mesoporous carbon adsorbent showed excellent dynamical separation stability, which ensured its great potential in practical molecular separations.

Controllable Phosphorylation Strategy for Free-Standing Phosphorus/Nitrogen Cofunctionalized Porous Carbon Monoliths as High-Performance Potassium Ion Battery Anodes.

A hard carbon material with free-standing porous structure and high contents of heteroatom functional groups is considered to be a potential anode for potassium-ion batteries (PIBs). Herein, a free-standing phosphorus/nitrogen cofunctionalized porous carbon monolith (denoted as PN-PCM) anode for PIBs is successfully fabricated via a supercritical CO2 foaming technology, followed by amidoximation, phosphorylation, and thermal treatment. Thanks to the synergistic effect of a three-dimensional macroporous open structure and high P/N contents of 6.19/5.74 at%, the PN-PCM anode delivers an excellent reversible specific capacity (396 mA h g-1 at 0.1 A g-1 after 300 cycles) with high initial Coulombic efficiency (63.6%), a great rate performance (168 mA h g-1 at 5 A g-1), and an ultralong cycling stability (218 mA h g-1 at 1 A g-1 after 3000 cycles). Theoretical calculations clarify that in a P/N cofunctionalized carbon, the P-C bonds devote more to enhancing the potassium storage via adsorption and improving electronic conductivity of carbon, while P-O bonds contribute more to enlarging the interlayer distance of carbon and reducing the ion diffusion barrier.

Novel Method of Fabricating Free-Standing and Nitrogen-Doped 3D Hierarchically Porous Carbon Monoliths as Anodes for High-Performance Sodium-Ion Batteries by Supercritical CO2 Foaming.

Sodium-ion batteries (SIBs), a promising candidate for large-scale energy storage systems, have recently attracted significant attention because of the low cost and high availability of the sodium resource. Hard carbon with a free-standing structure and plenty of active sites is considered to be the most potential anode material for SIBs. However, keeping a balance between the excellent performance and low cost for the large-scale commercial production of carbon anodes is still a great difficulty. Herein, a free-standing nitrogen-doped 3D hierarchically porous carbon monolith (denoted as 3DHPCM) anode for SIBs is successfully fabricated via a novel supercritical CO2 foaming technology and thermal treatment. Thanks to the tunable macro-meso-microporous and disordered structures, the 3DHPCM exhibits a high reversible specific capacity (281 mA h g-1 after 300 cycles at 50 mA g-1), superior rate performance (67 mA h g-1 at 10 A g-1), and excellent long-term cycling stability (175 mA h g-1 after 3000 cycles at 500 mA g-1). Remarkably, the 3DHPCM with such a high performance is fabricated via an environmentally friendly strategy from low-cost polyacrylonitrile and polymethyl methacrylate. Therefore, the strategy has great potential in practical application for fabricating high-performance hard carbon anodes and other composite electrodes for SIBs and more energy storage devices.

Self-Sacrificial Salt Templating: Simple Auxiliary Control over the Nanoporous Structure of Porous Carbon Monoliths Prepared through the Solvothermal Route.

The conventional sol-gel method for preparing porous carbons is tedious and high-cost to prepare porous carbons and the control over the nanoporous architecture by solvents and carbonization is restricted. A simple and novel self-sacrificial salt templating method was first presented to adjust the microporous structure of porous carbon monoliths synthesized via the solvothermal method. Apart from good monolithic appearance, the solvothermal route allowed for ambient drying because it made sure that the polymerization reaction was completed quickly and thoroughly. The intact and crack-free porous carbon monoliths were investigated by scanning electron microscopy (SEM), thermogravimetric differential scanning calorimetry (TG-DSC), Fourier transform infrared (FT-IR), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and nitrogen sorption measurements. It was proven that the self-sacrificial salts NH4SCN had been removed during pyrolyzing and so, porous carbon monoliths could be directly obtained after carbonization without the need of washing removal of salts. Most importantly, the microporous specific surface area of the resultant porous carbon monoliths was dramatically increased up to 770 m²/g and the Brunauer⁻Emmett⁻Teller (BET) specific surface area was up to 1131 m²/g. That was because the salts NH4SCN as self-sacrificial templating helped to form more around 0.6 nm, 0.72 nm and 1.1 nm micropores. The self-sacrificial salt templating is also a suitable and feasible method for controlling the nanoporous structure of other porous materials.

Nanocrystalline celluloses-assisted preparation of hierarchical carbon monoliths for hexavalent chromium removal.

Hierarchical porous carbon monoliths with a 3D framework were synthesized through a facile sol-gel process using resorcinol-melamine-formaldehyde (RMF) as carbon precursors, and nanocrystalline celluloses (NCCs) as the structural inducing agent, followed by ambient pressure drying and carbonization. Polymerization of the RMF resin occurs around the nanorod-like NCCs dispersed homogeneously in water, which is quite beneficial for the formation of an interconnected network and supports the rigid macroporous structure. A hierarchical porous carbon monolith with modest micropores and well-developed macropores was prepared after CO2 activation at 950°C. The microporous structure was generated from the network of RMF polymer chains, while the macroporous structure was formed from the interconnection of polymer networks induced by NCCs. The obtained carbon monolith has a large specific surface area of 1808m2g-1 and shows a high adsorption capacity of 463mgg-1 for toxic Cr(VI) ions. Moreover, the activated carbon monolith exhibits a high selectivity for Cr(VI) in the coexistence of several other metal ions. These outstanding advantages of carbon monoliths, including their micro/macroporous structures, rich functional groups, low cost and easy synthesis, endow them with potential for use in a wide range of applications.

Ultra-High Pyridinic N-Doped Porous Carbon Monolith Enabling High-Capacity K-Ion Battery Anodes for Both Half-Cell and Full-Cell Applications.

An ultrahigh pyridinic N-content-doped porous carbon monolith is reported, and the content of pyridinic N reaches up to 10.1% in overall material (53.4 ± 0.9% out of 18.9 ± 0.4% N content), being higher than most of previously reported N-doping carbonaceous materials, which exhibit greatly improved electrochemical performance for potassium storage, especially in term of the high reversible capacity. Remarkably, the pyridinic N-doped porous carbon monolith (PNCM) electrode exhibits high initial charge capacity of 487 mAh g-1 at a current density of 20 mA g-1 , which is one of the highest reversible capacities among all carbonaceous anodes for K-ion batteries. Moreover, the K-ion full cell is successfully assembled, demonstrating a high practical energy density of 153.5 Wh kg-1 . These results make PNCM promising for practical application in energy storage devices and encourage more investigations on a similar potassium storage system.