John P. Ferraris

Carbon molecular sieve membranes (CMSMs) provide a means to greatly improve gas separations. CMSMs have a pore size distribution comprising micropores and ultramicropores which provide high flux and high selectivity, enabling them to outperform polymeric membranes. CMSMs, however, suffer from physical aging that results from the collapse of the pores that severely reduces their gas permeability. Therefore, reducing physical aging of CMSMs is an important step in the development of these types of materials. In this work, a method for reducing physical aging through the incorporation of metal nanoparticles that serve as a structural scaffold for the membrane pore structure is presented. The pore structure in CMSMs is dependent upon the polymeric precursor, and thus the support system incorporated must be tailored. The copper nanoparticles were formed in situ from soluble, copper-based metal–organic polyhedra 18 (MOP-18) dispersed into Matrimid^® 5218, a low free volume polymer. The size (2 to 20 nm) and shape (sphere, rods) of the copper particles were refined by adjusting MOP-18 loading, pyrolysis temperature, and soaking time. The Cu-pillared Matrimid^® 5218 CMSMs from this work showed no decline in permeability or selectivity for methane (107 Barrer) and carbon dioxide (1785 Barrer) over a period of 21 d. The results suggest that tailored metal pillars can suppress physical aging in CMSMs, thereby enhancing their long-term stability and applicability in gas separations.

Carbon nanorods have been synthesized from acetylene and steam using europium oxide nanorods as a template. The resulting carbon exhibits a high conductivity of 4.66 × 10⁵ S/m and a surface area of 1226 m²/g. The Eu₂O₃ was partially or completely washed from the carbon, creating hollow nanorods. Hybrid supercapacitors were fabricated where the Eu₂O₃ contributes a redox pseudocapacitance. A gravimetric capacitance of 501.2 F/g for the hybrid cell and 202 F/g for the carbon-only cell was measured at 1 A/g using 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in propylene carbonate as an electrolyte. The hybrid supercapacitor exhibited an excellent energy density of 108 Wh/kg at 1 A/g compared to 43 Wh/g at 1 A/g for the carbon-only supercapacitor.

The necessity for substantial advancements in electrical energy storage systems is underscored by the increasing demand driven by the extensive integration of renewable energy sources into the grid, the growing popularity of hybrid and electric vehicles, and the escalating safety requirements. Supercapacitors, characterized by their high-power density, inherently superior safety features, and longer cycle life compared to other energy storage systems, are poised to meet these escalating expectations. In this research, an in situ dispersion of Metal-Organic Polyhedra (MOP)-18 in Matrimid is employed to construct a hybrid supercapacitor electrode with enhanced redox activity and improved electrical conductivity. A uniform solution of Matrimid and MOP-18 was electrospun, subsequently carbonized, and activated with CO₂ to yield Cu/Cu₂O decorated carbon fiber electrode materials. The remarkable solubility of MOP-18 was leveraged to ensure the even dispersion of nanoparticles. The thermally decomposable porous structure of MOP-18 augmented the surface area and electrolyte accessibility of the fabricated electrode. Conversely, Matrimid provided a highly conductive free-standing carbon for the electrode. The amalgamation of these factors culminated in a notable enhancement in capacitance and energy density in a 6 M KOH electrolyte solution. The synthesized composite material achieved a peak capacitance of 253 Fg^-1 and an energy density of 12.5 Whkg^-1 at a current density of 1 Ag^-1. The materials, methods, and techniques employed in the study can be readily scaled up industrially without significant alterations. As illustrated in the study, the use of soluble metal-organic structures to deliver redox-active materials in highly conductive carbon can result in composite electrode materials with synergistic properties. Figure 1

Increased energy consumption has triggered the development of various energy storage devices. Supercapacitors have gained attention as energy storage devices due to their high-power density and long cycle life. The energy density of supercapacitor can be increased by combining electric double layer capacitance (EDLC) and pseudocapacitance (PC). A hybrid material based on rare-earth metal oxide templated carbon will be presented that combines both EDLC and PC within the same material. Specifically, neodymium hydroxide (Nd(OH)₃) reacted with acetylene and steam to form carbon coated Nd₂O₃. Both Nd(OH)₃ nanorods and nanospheres were used to prepared templated carbon followed by partial or complete washing of metal oxide. The resulting carbon exhibit the surface area of 1245 m²/g. Asymmetric coin cell was constructed with capacitance of 180.5 F/g and energy density of 76.8 Wh/kg This work paves the door to develop novel hybrid supercapacitors.

The use of immiscible polymer blends in gas separations is limited due to uncontrollable phase separation. In contrast, compatibilized immiscible polymer blends can be used as precursors with controlled morphologies that allow for a unique pore architecture. Herein, an immiscible polymer blend (1:1) comprising polybenzimidazole (PBI) and the copolyimide 6FDA-DAM:DABA [3:2], derived from reacting 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 2,4,6-trimethyl-1,3-phenylenediamine (DAM) and 3,5-diaminobenzoic acid (DABA), were combined with durene diamine as a compatibilizer. The compatibilizer helped reduce the 6FDD domain sizes from 5.6 µm down to 0.77 µm and induced a more even 6FDA distribution and the formation of continuous thin-selective PBI layers. The carbon–carbon composite membranes derived from the compatibilized immiscible polymer blends showed a 3-fold increase in both H₂ permeability and H₂/CO₂ selectivity compared to the membranes derived from non-compatibilized polymer blends. The H₂ permeability of the compatibilized immiscible polymer blends increased from 3.6 to 27 Barrer, and their H₂/CO₂ selectivity increased from 7.2 to 20. The graphitic domain size of the carbon–carbon composite membranes derived from the polymer blends also increased from 6.3 nm for the non-compatibilized blend to 10.0 nm for the compatibilized blend.

Matrimid and metal-organic polyhedra–18 (MOP-18) electrospun composite nanofibers were utilized to fabricate free-standing, electrically conducting, and high-energy density hybrid supercapacitor electrodes. Electrospinning multiple compositions of Matrimid and MOP-18 mixture followed by carbonization and activation with CO₂ resulted in C/Cu/Cu₂O nanocomposite fibers that exhibited an energy density of up to 12.69 Wh/kg and a specific capacitance of 253.4 F/g at 1 A/g current density in 6 M KOH electrolyte. The high energy density of the material can be attributed to the uniform dispersion of redox-active metal/metal oxide particles facilitated by the high solubility of the MOP-18 precursor. The thermal decomposition of MOP-18 during carbonization produced volatile species that increase the surface area and porosity of the resultant carbon allowing for better access of electrolyte ions during charging/discharging. Furthermore MOP-18 carbonization lowered the I_D/I_G of the composite electrodes, consistent with increased graphitization.

This study explores a simple method of fabricating hybrid supercapacitor electrodes, which could potentially broaden the application of this technology. The method involves electrospinning a uniform solution of Matrimid/Metal−Organic Polyhedra 18 (MOP−18) followed by carbonization at a relatively low temperature of 700 °C in air, rather than in an inert atmosphere, to create free−standing, redox−active hybrid supercapacitor electrodes. Additionally, the synthesis procedure requires no stabilization or activation steps, which enhances the cost effectiveness of the synthesized electrode materials. The resulting C/CuO composite was used as the working electrode, with a polyacrylonitrile (PAN)/Poly(methyl methacrylate) (PMMA) carbon nanofiber (CNF) electrode as the counter and 6 M KOH as the electrolyte in a T−cell configuration. The cell performance and redox activity were evaluated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS) and cycling stability tests. Additionally, the physical and chemical structures of the electrode materials were assessed using X−ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron spectroscopy (TEM), X−ray diffractometry (PXRD), surface area analysis and other characterization techniques. The electrode material demonstrated a specific capacitance of up to 206 F/g. Supercapacitors utilizing this material display an energy density of 10.3 Wh/kg (active material) at a current density of 1 A/g in electrochemical testing.