Hierarchically porous carbons (HPCs) with 1D to 3D network are attracting vast interest due to their potential technological application profile ranging from electrochemical capacitors, lithium ion batteries, solar cells, hydrogen storage systems, photonic material, fuel cells, sorbent for toxic gas separation and so on. Natural raw-materials such as biomass-biopolymer derived hierarchical nanostructured carbons are especially attractive for their uniform pore dimensions which can be adjustable over a wide range of length scales. Good electrical conductivity, high surface area, and excellent chemical stability are unique physicochemical properties which are responsible for micro/nanostructured porous carbon to be highly trusted candidate for emerging nanotechnologies. This review focuses on the ‘out-of-the-box’ synthetic techniques capable of deriving HPC with superior application profiles. The article presents the promising scope of accessing HPCs from (1) hard-templating, soft-templating, and non-templating routes, (2) biopolymers with a major focus on non-templating strategies. Subsequently, emerging strategies of hetero-atom doping in porous carbon nanostructures are discussed. The review will highlight the contribution of synergistic effect of macro–meso–micropores on a range of emerging applications such as CO2 capture, carbon photonic crystal sensors, Li–S batteries, and supercapacitor. Mechanism of ion transport and buffering, electrical double layer enhancement have been discussed in the context of pore structure and shapes. We will also show the differences of HPC and ordered mesoporous carbon (OMC) in terms of their synthesis strategies and choices of template for self-assembly. How the remarkable mechanical strength of the HPCs can be achieved by selecting self-assembling template, whereas collapse of mesostructure via decomposition of framework occurs due to poor thermal stability or high N-content of the carbon source will be discussed.

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Hierarchically porous carbon derived from polymers and biomass: effect of interconnected pores on energy applications

The aim of this review is to provide an exposition of some of the most recent applications of deep-eutectic solvents (DESs) in the synthesis of polymers and related materials. We consider that there is plenty of room for the development of fundamental research in the field of DESs because their compositional flexibility makes the number of DESs susceptible of preparation unlimited and so do the range of properties that DESs can attain. Ultimately, these properties can be transferred into the resulting materials in terms of both tailored morphologies and compositions. Thus, interesting applications can be easily envisaged, especially in those fields in which the preparation of high-tech products via low cost processes is critical. We hope that the preliminary work surveyed in this review will encourage scientists to explore the promising perspectives offered by DESs.

Deep-eutectic solvents playing multiple roles in the synthesis of polymers and related materials

High-surface-area N-decorated nanoporous carbons have been successfully synthesized using the N-rich metal–organic framework ZIF-8 as a template and precursor along with furfuryl alcohol and NH4OH as the secondary carbon and nitrogen sources, respectively. These carbons exhibited remarkable CO2 adsorption capacities and CO2/N2 and CO2/CH4 selectivities. The N-decoration in these carbons resulted in excellent activity for the oxygen reduction reaction. Samples NC900 and NC1000 having moderate N contents, high surface areas, and large numbers of mesopores favored the four-electron reduction pathway, while sample NC800 having a high N content, a moderate surface area, and a large number of micropores favored the two-electron reduction process.

From Metal–Organic Framework to Nitrogen-Decorated Nanoporous Carbons: High CO2 Uptake and Efficient Catalytic Oxygen Reduction

Business costs and energy/environmental concerns have increased interested in biomass materials for production of activated carbons, especially as electrode materials for supercapacitors or as solid-state adsorbents in CO2 adsorption area. In this paper, waste celtuce leaves were used to prepare porous carbon by air-drying, pyrolysis at 600 °C in argon, followed by KOH activation. The as-prepared porous carbon have a very high specific surface area of 3404 m2/g and a large pore volume of 1.88 cm3/g. As an electroactive material, the porous carbon exhibits good capacitive performance in KOH aqueous electrolyte, with the specific capacitances of 421 and 273 F/g in three and two-electrode systems, respectively. As a solid-state adsorbent, the porous carbon has an excellent CO2 adsorption capacity at ambient pressures of up to 6.04 and 4.36 mmol/g at 0 and 25 °C, respectively. With simple production process, excellent recyclability and regeneration stability, the porous carbon that was derived from celtuce le...

Promising Porous Carbon Derived from Celtuce Leaves with Outstanding Supercapacitance and CO2 Capture Performance

A series of carbon spheres (CS) was prepared by carbonization of phenolic resin spheres obtained by the one-pot modified Stober method. Activated CS (ACS), having diameters from 200 to 420 nm, high surface area (from 730 to 2930 m2/g), narrow micropores (<1 nm) and, importantly, high volume of these micropores (from 0.28 to 1.12 cm3/g), were obtained by CO2 activation of the aforementioned CS. The remarkably high CO2 adsorption capacities, 4.55 and 8.05 mmol/g, were measured on these AC spheres at 1 bar and two temperatures, 25 and 0 °C, respectively.

Activated carbon spheres for CO2 adsorption.

Unprecedented CO2 uptake over highly porous N-doped activated carbon monoliths prepared by physical activation.

Fabrication of mesoporous polymer monolith: a template-free approach.

Mesoporous polyacrylonitrile (PAN) monoliths have been prepared by thermally induced phase separation technique (TIPS) using the unique affinity of PAN towards a mixture of water/dimethyl sulphoxide (DMSO). The overall microstructure, porosity and skeleton size of the polymer monoliths are controlled by optimizing the concentration of the polymer, ratio of water and DMSO, and the cooling temperature. The monoliths have been functionalized by amidoximation of the –CN functional groups in methanolic hydroxyl amine. The amidoximated PAN monoliths can be used as efficient ion-exchangers for the separation of different metal ions. On the other hand, the copper(II)-exchanged amidoximated monolith can be used as catalyst for oxidation of cycloalkanes and toluene under liquid-phase condition using mild oxidizing agent, tert-butyl hydroperoxide (TBHP).

Functional mesoporous polymer monolith for application in ion-exchange and catalysis

Disclosed is a method for producing a porous body that contains polyacrylonitrile as a main component, comprising the steps of obtaining a polyacrylonitrile solution by heating and dissolving this polyacrylonitrile in a solvent, obtaining a molded body by cooling and precipitation from this polyacrylonitrile solution, separating and drying this molded body and obtaining a porous body containing polyacrylonitrile as a main component. The solvent contains a poor solvent for polyacrylonitrile and a good solvent for polyacrylonitrile.

Polyacrylonitrile porous body

A poly(acrylonitrile) monolith having a three-dimensionally developed, continuous porous structure was uniformly coated with carbon nanotubes (CNTs) just by dipping the monolith in an aqueous dispersion of CNTs. This simple procedure successfully realized the modification of the monolith surface with the electron-conductive material. Cyclic voltammetry showed that electrochemical capacitance was indeed imparted to the CNT-coated monolith. © The Electrochemical Society of Japan, All rights reserved.

Keisuke Okada

Papers

Unprecedented CO2 uptake over highly porous N-doped activated carbon monoliths prepared by physical activation.

Fabrication of mesoporous polymer monolith: a template-free approach.

Functional mesoporous polymer monolith for application in ion-exchange and catalysis

Polyacrylonitrile porous body

Fabrication and Electrochemical Capacitive Behaviors of a Carbon Nanotube-Coated Polymer Monolith