Nitrogen-enriched Porous Carbons Research Articles

N-doped porous carbon derived from macadamia nut shell for CO2 adsorption

Selective adsorption and converting CO2 upon efficient solid-based adsorbents is critical for net-zero accomplishment. Herein, we develop an advisable strategy to prepare nitrogen-enriched porous carbons using the macadamia nutshell (MNS) as a carbon precursor, KOH as the activator and melamine as the nitrogen agent, respectively. The as-prepared porous carbons exhibit an enhanced specific surface area of 1731 m2/g and high microporosity with abundant nitrogen functional groups and structural defects. The CO2 uptake of 6.61 and 4.35 mmol g−1 were achieved at 0 and 25 °C, respectively, under 1 bar. More importantly, these biomass-based nitrogen-doped carbons possess various CO2 adsorption merits such as quick adsorption kinetics, high CO2/N2 selectivity, medium heat of adsorption, outstanding uninterrupted recyclability and good dynamic CO2 capture capacity. The present study provides an advanced protocol to design nitrogen-doped porous Carbon via a facile route toward the capture of CO2, which offers excellent progress in sustainable chemistry and engineering.

Effective CO2 adsorption at low pressure over nitrogen-enriched porous carbons, derived from melamine-loaded polyaniline

Polyaniline (PANI)-derived carbon has been applied in various adsorptions because of the presence of nitrogen and relatively high porosity. In this study, melamine/PANI mixture was pyrolyzed at low temperatures (500–650 °C) to derive porous carbons with high nitrogen content because of added melamine. Obtained carbons (Melamine/PANI-derived Carbons, MPCs) were characterized and applied in CO2 adsorption under low pressure, and MPC-550 (prepared at 550 °C) showed much better performance than PC-550, derived from pure PANI, because of high N content (since N leads to polarity and basicity, which are helpful for CO2 adsorption) and narrow pores (even with low porosity). For example, MPC-550 and PC-550 (prepared at 550 °C) had adsorption capacity of 1.2 and 1.0 mmol/g (at 0.15 atm); and isosteric heat of adsorption (IHA) at zero coverage of 46 and 32 kJ/mol, respectively. On the other hand, N2 adsorption relied mainly on porosity; therefore, MPC-550 had lower N2 adsorption than PC-550. Accordingly, MPC-550 and PC-550 showed ideal adsorbed solution theory selectivity (CO2/N2) of 75 and 61, respectively, under 1 atm. MPC-550 had competitive selectivity compared with other carbon-based adsorbents. MPC-500, prepared at 500 °C, showed very high selectivity (110) and IHA (48 kJ/mol); however, had relatively low CO2 adsorption because of low porosity. Based on the advantages of MPC-550, compared with those of PC-550, adding nitrogenous compounds (like melamine) to PANI, before pyrolysis, is one of the recommendable methods for porous carbons, especially with high N content. Finally, MPC-550 was recyclable in CO2 adsorption and can be suggested as a promising adsorbent for CO2 capture from offgas.

Remarkable adsorbent for removal of bisphenol A and S from water: Porous carbon derived from melamine/polyaniline

Recently, contamination of water resources with various organics such as bisphenols is a problem worldwide. Here, we developed nitrogen-enriched porous carbons (N-PDCs) from pyrolysis of melamine-loaded polyaniline (PANI), for the first time. The N-PDCs and PANI-derived carbons (PDCs, without using melamine) were characterized and applied in adsorptive removal of two typical bisphenols, such as bisphenol A and S (BPA and BPS, respectively), from water under a wide range of conditions. Via this research, we found that one N-PDC (N-PDC-700, obtained at 700 °C) showed very remarkable performances in adsorption of BPA (Q0: 961 mg/g) and BPS (Q0: 971 mg/g) under pH of 7.0. In other words, N-PDC-700 has Q0 value for BPS around 2 times as much as that of the most effective adsorbent, MIL-101-NH2. Moreover, the Q0 value of N-PDC-700 for BPA is the second highest, after the sp2 C dominant N-doped carbon. The plausible adsorption mechanism could be suggested based on the adsorption of BPA under a wide range of pH values. Finally, the N-PDC-700 was easily recycled for several uses, suggesting the potential application in adsorption of bisphenols from water.

Silicate-assisted activation of biomass towards N-doped porous carbon sheets for supercapacitors

Biomass-derived carbon has been the focus of research for a long time due to its wide range of sources, rich diversity and low cost. However, it also faces poor pore size distribution, low surface area and inert surface, which leads to its low performance, especially in supercapacitor. Herein, nitrogen enriched porous carbons (N-PC) were synthesized via a simple silica-activation process using carrots biomass as carbon precursor and Na2SiO3 as effective activation agent. Direct grinding for mixing of carrots and Na2SiO3 avoids the utilization of any solvents, leading to the characteristics of easy operation, simplicity and large-scale application. Carrots are rich in vitamins, which makes them serve as excellent carbon and nitrogen precursor. The low-cost Na2SiO3 plays an activating role to create porous structure, realizing the adjustment of mesopore size and increasing surface area for the N-PC. The prepared N-PC exhibits layered morphology, high surface area, rich porous structure, and nitrogen doping, which endow the N-PC with outstanding performance in the field of supercapacitor, indicating its promising for energy storage application.

Superiority of Raw Biomass and Potassium Hydroxide in Preparation of Ultrahigh Nitrogen Doping of Carbon for NH3-SCR Reaction

Developing nitrogen-enriched porous carbons using inexpensive and easily accessible biomass remains a great challenge in recent years. Herein, a series of nitrogen-doped porous carbons were prepare...

Ultrastable Surface-Dominated Pseudocapacitive Potassium Storage Enabled by Edge-Enriched N-Doped Porous Carbon Nanosheets.

The development of ultrastable carbon materials for potassium storage poses key limitations caused by the huge volume variation and sluggish kinetics. Nitrogen‐enriched porous carbons have recently emerged as promising candidates for this application; however, rational control over nitrogen doping is needed to further suppress the long‐term capacity fading. Here we propose a strategy based on pyrolysis–etching of a pyridine‐coordinated polymer for deliberate manipulation of edge‐nitrogen doping and specific spatial distribution in amorphous high‐surface‐area carbons; the obtained material shows an edge‐nitrogen content of up to 9.34 at %, richer N distribution inside the material, and high surface area of 616 m2 g−1 under a cost‐effective low‐temperature carbonization. The optimized carbon delivers unprecedented K‐storage stability over 6000 cycles with negligible capacity decay (252 mA h g−1 after 4 months at 1 A g−1), rarely reported for potassium storage.

Nitrogen enriched porous carbons from d-glucose with excellent CO2 capture performance

In this study, nitrogen-enriched porous carbonaceous sorbents were successfully prepared by co-hydrothermal treatment of d-glucose and urea, followed by KOH activation under different conditions. Using this new synthesis strategy, the as-prepared adsorbents show a high nitrogen content ranging from 6.20 to 12.17 wt%. In addition, these sorbents also have highly developed porous texture including high narrow microporosity. The optimal sample exhibits the high CO2 uptake of 4.26 and 6.70 mmol/g at 25 and 0 °C, respectively, at 1 bar. Additional study finds that both narrow micropores and nitrogen content are important in deciding the CO2 adsorption ability for these adsorbents under ambient conditions. Besides the high CO2 adsorption ability, these adsorbents also demonstrate stable recyclability, high selectivity of CO2 over N2, suitable heat of adsorption, rapid adsorption kinetics, as well as excellent dynamic CO2 uptake. The above-mentioned excellent CO2 adsorption performance together with the low cost of precursor and facile synthesis strategy prove that these glucose-based porous carbonaceous sorbents are a potential candidate for industrial capture of CO2.

Impact of Carbon Support Functionalization on the Electrochemical Stability of Pt Fuel Cell Catalysts

Nitrogen-enriched porous carbons have been discussed as supports for Pt nanoparticle catalysts deployed at cathode layers of polymer electrolyte membrane fuel cells (PEMFC). Here, we present an analysis of the chemical process of carbon surface modification using ammonolysis of preoxidized carbon blacks, and correlate their chemical structure with their catalytic activity and stability using in situ analytical techniques. Upon ammonolysis, the support materials were characterized with respect to their elemental composition, the physical surface area, and the surface zeta potential. The nature of the introduced N-functionalities was assessed by X-ray photoelectron spectroscopy. At lower ammonolysis temperatures, pyrrolic-N were invariably the most abundant surface species while at elevated treatment temperatures pyridinic-N prevailed. The corrosion stability under electrochemical conditions was assessed by in situ high-temperature differential electrochemical mass spectroscopy in a single gas diffusion lay...

Synthesis of nitrogen enriched porous carbons from urea formaldehyde resin and their carbon dioxide adsorption capacity

Carbon dioxide capture needs development of cost effective CO2 capture technologies. This paper describes nitrogen enriched porous carbons synthesized from nanocasting technique using mesoporous silica as template and urea-formaldehyde resin as precursor. These carbon materials were evaluated as sorbents for CO2 capture by using a thermogravimetric analysis under dynamic conditions. Carbonization and physical activation with CO2 at different temperatures (500–800°C) were carried out that resulted in the generation of different carbon adsorbents containing nitrogen functional groups. The textural characterization result reveals effect of nanocasting technique, which is confirmed from the generation of mesopores (0.644cm3g−1), micropores (0.123cm3g−1) and high surface area (337.07m2g−1) of adsorbent. The CO2 capture capacity depends more on the nitrogen functionalities in addition to textural properties and nitrogen content, as the sample synthesized at 700°C shows highest uptake capacity of 1.3mmolg−1. Furthermore, it was found that adsorbent can be easily regenerated, which was also seen by the lower value of isosteric heat of adsorption. Ten adsorption-desorption cycles show established materials’ excellent stability as an adsorbent. Different kinetic models were fitted for the adsorption data and on the basis of correlation coefficient (R2), fractional order provided best fit with the experimental data. The heterogeneous nature of the adsorbent surface was seen by best fitting of Freundlich isotherm and from the pattern of isosteric heat of adsorption. Exothermic, spontaneous and feasible nature was suggested by thermodynamic parameters’ values. The thermal energy needed for desorption of CO2 from the adsorbent surface was around 1.28MJ per kg CO2.

Conjugated Microporous Polycarbazole Networks as Precursors for Nitrogen-Enriched Microporous Carbons for CO2 Storage and Electrochemical Capacitors

The design and synthesis of novel microporous materials have received tremendous attention in both CO2 storage and sequestration (CSS) and electrochemical energy storage (EES). We report molecular design and synthesis of conjugated microporous polycarbazole networks as new precursors for nitrogen-enriched porous carbons. As-prepared porous carbons exhibit a high nitrogen content (6.1 wt %), ultramicropore size (0.7–1 nm), and large surface area (1280 m2 g–1). As a result, these novel nitrogen-enriched carbons show highly efficient and reversible CO2 capture (can store 20.4 wt % at 1 bar and 11.1 wt % at 0.15 bar and at 273 K, while maintaining 100% CO2 uptake capacity after five cycles). Moreover, they can be applied as electrodes and enable high-performance EES devices with a fast charge/discharge rate (8 s), high electrochemical capacity (558 F g–1), and good cycle ability (retain 95% capacity after 1000 cycles).

Functional Groups and Pore Size Distribution Do Matter to Hierarchically Porous Carbons as High-Rate-Performance Supercapacitors

A series of nitrogen and oxygen enriched porous carbons are prepared from poly-N-phenylethanolamine (PNPEA) and polyaniline (PANI) conducting polymers through pyrolysis, chemical activation, and oxidation processes. Ar or N2-adsorption, Fourier transform infrared, and X-ray photoelectron spectroscopy are used to characterize the surface areas, pore volumes, surface chemical compositions, and oxygen and nitrogen content. Mikhail and Brunauer micropore analytical method (MP method) is successfully used to analyze the micropore size distribution of the samples. The electrochemical behavior of the samples is studied in two- and three-electrode cells. The contribution of pseudocapacitance is confirmed by cyclic voltammetry and galvanostatic tests performed in acidic (H2SO4) and basic (KOH) media. The potential drop and the equivalent series resistance value certify that the samples with wide micropore size distribution possess low interface resistances. A sample with a Brunauer–Emmett–Teller (BET) surface area...

Nitrogen-enriched carbonaceous materials with hierarchical micro-mesopore structures for efficient CO2 capture

Carboxyl-rich porous carbons (CPCs) derived from glucose are prepared by a hydrothermal method in the presence of acrylic acid and non-ionic surfactant Brij 72 as structure-directing agents. Tetraethylenepentamine molecules are then grafted onto the surfaces of CPCs via acylation–amidation route, yielding nitrogen-enriched porous carbons (NPCs). Material characterizations reveal that the CPCs display high surface areas with micro and mesoporous structures. Despite the surface functionalization of CPCs via acylation–amidation route the porous structures of NPCs are maintained. As a result, the NPCs exhibit excellent CO2 capture capacity (3.2mmolg−1) with high selectivity of CO2 over N2 (>46) at 298K and 1bar. In addition, good reversibility of CO2 adsorption can be achieved at different temperatures.