Charge storage mechanism in nanoporous carbons and its consequence for electrical double layer capacitors

Electrochemical capacitors, also known as supercapacitors, are energy storage devices that fill the gap between batteries and dielectric capacitors. Thanks to their unique features, they have a key role to play in energy storage and harvesting, acting as a complement to or even a replacement of batteries which has already been achieved in various applications. One of the challenges in the supercapacitor area is to increase their energy density. Some recent discoveries regarding ion adsorption in microporous carbon exhibiting pores in the nanometre range can help in designing the next generation of high-energy-density supercapacitors

Porous Graphene-like Carbon from Fast Catalytic Decomposition of Biomass for Energy Storage Applications

A novel carbon material made of porous graphene-like nanosheets was synthesized from biomass resources by a simple catalytic graphitization process using nickel as a catalyst for applications in electrodes for energy storage devices. A recycled fiberboard precursor was impregnated with saturated nickel nitrate followed by high-temperature pyrolysis. The highly exothermic combustion of in situ formed nitrocellulose produces the expansion of the cellulose fibers and the reorganization of the carbon structure into a three-dimensional (3D) porous assembly of thin carbon nanosheets. After acid washing, nickel particles are fully removed, leaving nanosized holes in the wrinkled graphene-like sheets. These nanoholes confer the resulting carbon material with ≈75% capacitance retention, when applied as a supercapacitor electrode in aqueous media at a specific current of 100 A·g–1 compared to the capacitance reached at 20 mA·g–1, and ≈35% capacity retention, when applied as a negative electrode for lithium-ion battery cells at a specific current of 3720 mA·g–1 compared to the specific capacity at 37.2 mA·g–1. These findings suggest a novel way for synthesizing 3D nanocarbon networks from a cellulosic precursor requiring low temperatures and being amenable to large-scale production while using a sustainable starting precursor such as recycled fiberwood.Spanish Government Agency Ministerio de Economí a y Competitividad (MINECO) (grant number MAT2016-76526-R)

CO2 storage properties of nanostructured carbons by a microwave plasma reactor

Nanostructured carbon was successfully produced by methane cracking in a relatively low-energy cold plasma reactor designed in-house. A followed thermal treatment was carried out to further enhance its porosity. The modified plasma carbon was then employed for CO2 adsorption at 25°C. The as-synthesized plasma carbon and the modified carbon were characterized by BET surface area/pore size analyzer, Raman spectra, and transmission electron microscopy (TEM). The results show thermal modification pronouncedly improves BET surface area and porosity of PC due to opening up of accessible micro-/mesopores in the graphitic structure and by the removal of amorphous carbons around the graphite surface. The modified PC displays a higher adsorption capacity at 25°C than that of the commercial activated carbon reported. The low hydrogen storage capacity of the modified PC indicates that it can be considered for CO2 removal in syngas

Synthesis of carbon nanotubes-mesostructured silica nanoparticles composites for adsorption of methylene blue

The mesostructured silica nanoparticles (MSN) have been widely developed for the removal of various pollutants due to their highly porous structure and other novel features. While carbon nanotubes (CNT) are attracting great interest owing to its large specific surface area, small size, hollow and layered structures. The integration of these outstanding properties by modification of MSN with singlewalled CNT (SWCNT) and multiwalled CNT (MWCNT) is quite new in this area of study and is expected to produce an adsorbent with higher adsorption capacity. In this study, three types of adsorbents were prepared by a simple one step method; MSN, series of SWCNT-MSN composites, and series of MWCNT-MSN composites. Their characteristics have been observed by XRD, N2 physisorption, FTIR, TEM, and FESEM, while their adsorption performance were evaluated on the adsorption of methylene blue (MB) at various pH, adsorbent dosage, initial MB concentration, and temperature. The results demonstrated that the adsorbents were prepared with mesoporous structures and produces relatively higher number of pores with larger diameters. The CNTs were found to improve the physicochemical properties of the MSN and led to an enhanced adsorptivity for MB. N2 physisorption measurements revealed the development of a bimodal pore structure in MWCNT-MSN composites that increased the pore size, pore volume and surface area. The best conditions for MSN, SWCNT-MSN and MWCNT-MSN composites achieved at pH 7 and 303 K using 0.05 g L-1 adsorbent and 100 mg L-1 MB. Fitting with linear Langmuir isotherm produce the maximum adsorption capacity of 500.1 mg g-1, 500.0 mg g-1, and 263.2 mg g-1 for MSNAP, SWCNT-MSN and MWCNT-MSN, respectively. The equilibrium data were evaluated using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models, with the Freundlich model affording the best fit to the adsorption data for MSN and Langmuir model for both SWCNT-MSN and MWCNT-MSN. The adsorption kinetics for all MSN, SWCNT-MSN and MWCNT-MSN were best described by the pseudo-second order model. Thermodynamic study showed that the nature of MSNs and MWCNT-MSNs are exothermic, and endothermic for SWCNT-MSNs. This study is proven to produce a relatively new and potential mesostructured materials used as adsorbent for dye removal and water treatment

Hierarchical Engineering of Multimodal Ordered Nanoporous Materials

Nanoporous materials have attracted extensive research interest owing to their potential for applications spanning arenas as diverse as energy (e.g., catalysts, separations), the environment (e.g., sorbents), and health (e.g., drug delivery). The ability to achieve tunable control over pore size, dimensionality, and specific pore topology is a persistent challenge when it comes to rational synthesis of micro-, meso-, and/or hierarchically-porous materials. In this thesis, we develop a multiscale synthetic strategy and its fundamental physicochemical underpinnings for realizing nanoporous and hierarchically porous materials with three-dimensionally ordered pores spanning classes of nanoporous materials as diverse as amorphous mesoporous silicas, micro-mesoporous carbons, and crystalline microporous zeolites. We also demonstrate the versatility of this approach in terms of material morphology from porous particles/powders to thin films.We establish strategies for bottom-up assembly of binary silica nanoparticles for realizing template-free ordered mesoporous silicas (OMSs). We first study the phase behavior of evaporation-induced convective assembly of binary silica nanoparticles, and show that even without specific solvent index matching or stabilization beyond intrinsic properties of the amino acid nanoparticle synthesis solution, symmetry of the binary assemblies is governed solely by particle size ratio, consistent with binary hard-sphere predictions. The demonstrated robustness of the binary nanoparticle assembly and the control over silica particle size translate to a facile, template-free approach to OMSs with independently tunable pore topology associated with the interstices of AB, AB2 , AB13, and AB interstitial nanoparticle crystals that are isostructural with NaCl, AlB2, and NaZn13. Moreover, we elucidate the role of the amino acid, L-lysine, employed in the nanoparticle synthesis, the structural evolution of the silica network upon aging of dialyzed nanoparticle sols, and substrate character in tuning particle stability and thereby the yield of ordered binary assemblies achievable in both bulk and thin film morphologies.We subsequently employ these novel multi-modal OMSs as sacrificial hard templates in realizing a facile method to synthesize a new class of bimodal three-dimensionally ordered mesoporous (b-3DOm) carbons with tunable bimodal mesoporosity. Continuously adjustable bimodal mesoporosity in the range of 15-23 nm for small pores and 40-50 nm for large pores with controlled pore topology is confirmed. Attractive textural properties result, including high surface areas (\u3e1000 m2/g), narrow pore size distributions, and large pore volumes (2-5 cm3/g). The structural stability of these large-pore volume materials is underscored by the pore robustness upon removal of the hard sacrificial silica template and even in the face of carbon loss during subsequent activation of microporosity in the carbon walls. We conclude the thesis by demonstrating a top-down strategy to scaffold the growth of ultra-thin crystalline microporous (zeolite) films. Here, we combine nanoparticle crystal-templated carbon thin films to force in-plane crystal growth. Through tuning of nucleation and growth within the carbon film scaffolds, the strategy developed in this thesis enables realization of large silicalite-1 crystal regions formed by intergrowth of separately nucleated crystal domains. The thickness of the silicalite-1 domains can be tuned and scaled down to the order of 10 nm by controlling the carbon scaffold thickness, with remarkable flexibility of the inorganic films observed