Nitrogen-doped Carbon Monoliths Research Articles

High yield nitrogen-doped carbon monolith with rich ultramicropores prepared by in-situ activation for high performance of selective CO2 capture

Constrained by the unsatisfactory physical adsorption capacity and the low carbon yield from chemical activation, practical utilization of carbon materials for CO2 capture and separation (CCS) remains a huge challenge. Herein, we proposed a novel in-situ activation methodology to prepare a category of porous carbon monoliths in which the potassium ion activation sites are evenly introduced through acid-base reaction, contributing to the high carbon yield, abundant ultramicropores as well as rich nitrogen content. Tested at adsorption temperatures of 0, 25 and 40 °C, the as-prepared carbon monoliths display remarkable static CO2 uptake (7.1, 5.0 and 3.7 mmol/g, respectively) and excellent selective adsorption ability in dynamic breakthrough experiment with a binary mixture of CO2/N2 (68, 63 and 67, respectively). Along with the experiments, the CO2 adsorption mechanism was determined by calculating the adsorption density and adsorption energy on slit pore with various pore sizes and surface functionalities using grand canonical Monte Carlo (GCMC) simulation. The narrow micropores can significantly and effectively increase the CO2adsorption capacity, while the functional groups played the second role.

Carbon monoliths with programmable valence bands as de novo anodes for additive-free coupling of alcohols into acetals

Designing functional and reusable electrode materials to replace homogeneous versions of scarifying additives or mediators in electrochemical organic synthesis is of great importance for both the fundamental academics and practical production of various useful compounds. Herein, we rediscover the function of nitrogen-doped carbon monoliths (NxC) as de novo anode materials to trigger a new reaction path for the synthesis of acetals from the direct coupling of alcohols without the assistance of any mediator, oxidant, acid, or organic ligand. The lowered valence bands of carbon monoliths induced by doping nitrogen are of key importance for polarizing and activating the pre-adsorbed O–H groups of benzyl alcohol molecules to boost the high Faradaic efficiency (71% at 1.8 V versus Ag/AgCl) and reusability of NxC anodes, meeting the requirements of green chemistry.

Templated preparation of hierarchically porous nitrogen-doped carbon electrode material via a mild phase inversion route for high-performance supercapacitor

• Hierarchically porous nitrogen-doped carbon was prepared through a modified phase–inversion method. • Water vapor treatment induced the formation of mesopores in the whole carbon matrix. • Well-distributed macropores with uniform sizes were formed by using PVDF-HFP template. • The hierarchically porous structure and proper doping level endow the product with high and stable capacitive performances. By using poly (vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) as the template, a kind of nitrogen-doped carbon monolith with well-distributed hierarchical pores was prepared through a modified phase–inversion method. Due to the hierarchically porous structure and proper doping level, the synthesized electrode material delivered superior specific capacitances (312.2 F g −1 at 0.5 A g −1 and 217.6 F g −1 at 20 A g −1 ), as well as remarkable specific energy and power (7.1 Wh kg −1 at 250 W kg −1 ). More significantly, its high chemical and structural stability allow it to reach 109.7% of the original capacitance after 10,000 charge-discharge cycles at the current density of 20 A g −1 . The simple yet efficient synthetic strategy, unique porous structure, and thus the enhanced electrochemical capacitive performances of the prepared nitrogen-doped carbon not only make it a promising electrode material for energy storage devices, but also bring new ideas for the controllable preparation of polymer-derived hierarchically porous carbon materials. By using PVDF-HFP as the macropore template, nitrogen-doped carbon electrode material with hierarchically porous structure was prepared through non-solvent induced phase inversion process for high performance supercapacitors.

Porous nitrogen-doped carbon monoliths derived from biopolymer-structured liquid precursors

Nitrogen-doped carbon monoliths can be prepared from liquid, deep eutectic mixtures of urea and hexaketocyclohexane octahydrate, which are structured by chitosan as a natural in-situ scaffold and support. The as-formed polymer monolith can then be transformed into the respective nitrogen-doped carbon monolith with a high surface area, high mesoporosity and high nitrogen-content. The surface functionality as well as the access to the internal pore structure were demonstrated by carbon dioxide and dye sorption experiments. The applied synthetic procedure is simple, does not require additional activation steps and uses cheap and naturally abundant compounds avoiding typical and hazardous formaldehyde resins. Eventually, this offers a safe and sustainable alternative to current carbon monolith synthesis.

The carbonization temperature effect on the electrochemical performance of nitrogen-doped carbon monoliths

Three-dimensional flexible nitrogen-doped carbon monoliths (3DNC) were prepared by one-step carbonization method of commercially available melamine foam. The carbonization temperature effect on the electrochemical performance of nitrogen-doped carbon monoliths was investigated. With the increase of carbonization temperature, the specific capacitance of binder-free 3DNC electrode intensifies up to 221Fg−1 at a current density of 0.5Ag−1 at 950°C in 2M NaOH and weaken for higher temperature, which can be explained by the balance between nitrogen doping concentration and the specific surface area at different carbonization temperature. Further, the optimized 3DNC exhibits 96% retention after 5000 cycles measurements, indicating its superior long-term stability. Moreover, the assembled symmetric device outputs the maximum energy density of 9.34 Wh kg−1 as well as the maximum power density of 6.9kWkg−1. These results demonstrate the potential application of the designed 3DNC structures for energy storage devices.

The bakery of high-end sorption carbons: sugar–urea doughs as processable precursors for functional carbons

Porous nitrogen-doped carbon monoliths from processable doughs of liquid sugar-urea mixtures with salt and cellulose as porogen and filler, respectively.

A comparative study of nitrogen-doped hierarchical porous carbon monoliths as electrodes for supercapacitors

Two nitrogen-doped carbon monoliths with hierarchical porosity over a large size range were prepared by polymerization of resorcinol and formaldehyde in the presence of an organic amine, L-lysine, and an inorganic base, ammonium hydroxide under ambient conditions. Their physical and chemical features were characterized by N 2 sorption, transmission and scanning electron microscopy, and elemental analysis. Their electrochemical properties as the electrodes of supercapacitors were evaluated under both a three-electrode system and a two-electrode system. Results show that the two types of nitrogen-doped carbon possess similar pore structures, but have distinct electrochemical performances. The L-lysine incorporated carbon monolith has a high nitrogen content, a high specific capacitance of 199 F·g −1, and a 1.6% loss in the specific capacitance after 1000 charge-discharge cycles, indicating a long-term cycling stability.