Thomas E. Rufford

KOH catalysed preparation of activated carbon aerogels for dye adsorption.

Organic carbon aerogels (CAs) were prepared by a sol-gel method from polymerisation of resorcinol, furfural, and hexamethylenetetramine catalysed by KOH at around pH 9 using ambient pressure drying. The effect of KOH in the sol-gel on CA synthesis was studied. It was found that addition of KOH prior to the sol-gel polymerisation process improved thermal stability of the gel, prevented the crystallinity of the gel to graphite, increased the microporosity of CA and promoted activation of CA. The CAs prepared using the KOH catalyst exhibited higher porosity than uncatalysed prepared samples. Activation in CO(2) at higher temperature also enhanced the porosity of CAs. Adsorption tests indicated that the CAs were effective for both basic and acid dye adsorption and the adsorption increased with increasing surface area and pore volume. The kinetic adsorption of dyes was diffusion control and could be described by the second-order kinetic model. The equilibrium adsorption of dyes was higher than activated carbon.

A comparative study of chemical treatment by FeCl3, MgCl2, and ZnCl2 on microstructure, surface chemistry, and double-layer capacitance of carbons from waste biomass

The effect of chemical treatment on the capacitance of carbon electrodes prepared from waste coffee grounds was investigated. Coffee grounds were impregnated with FeCl3 and MgCl2 and then treated at 900 degrees C. The resultant carbons were compared with activated coffee ground carbons prepared by ZnCl2 treatment. The carbon treatment processes of FeCl3 and MgCl2 were studied using thermal gravimetric analysis. Raman spectroscopy, x-ray photoelectron spectroscopy, and N-2 and CO2 adsorption were used to characterize the activated carbons. Activation with ZnCl2 and FeCl3 produced carbons with higher surface areas (977 and 846 m(2)/g, respectively) than treatment with MgCl2 (123 m(2)/g). Electrochemical double-layer capacitances of the carbons were evaluated in 1 M H2SO4 using two-electrode cells. The system with FeCl3-treated carbon electrodes provided a specific cell capacitance of 57 F/g.

Nitrogen and phosphorous co-doped graphene monolith for supercapacitors

The co-doping of heteroatoms has been regarded as a promising approach to improve the energy-storage performance of graphene-based materials because of the synergetic effect of the heteroatom dopants. In this work, a single precursor melamine phosphate was used for the first time to synthesise nitrogen/phosphorus co-doped graphene (N/P-G) monoliths by a facile hydrothermal method. The nitrogen contents of 4.27-6.58 at% and phosphorus levels of 1.03-3.00 at% could be controlled by tuning the mass ratio of melamine phosphate to graphene oxide in the precursors. The N/P-G monoliths exhibited excellent electrochemical performances as electrodes for supercapacitors with a high specific capacitance of 183 F g(-1) at a current density of 0.05 A g(-1), good rate performance and excellent cycling performance. Additionally, the N/P-G electrode was stable at 1.6 V in 1 m H2 SO4 aqueous electrolyte and delivered a high energy density of 11.33 Wh kg(-1) at 1.6 V.

A review of conventional and emerging process technologies for the recovery of helium from natural gas

Helium is a unique gas with a wide range of important medical, scientific and industrial applications based on heliums extremely low boiling temperature, inert and non-flammable nature and small molecular size. The only practical sources of helium are from certain natural gas (NG) fields. As world demand for helium rapidly increases, the value of NG fields that contain it even in very small amounts is likely to rise significantly if the helium can be recovered efficiently. However, recovering the helium from the NG using conventional cryogenic distillation processes is expensive and energy intensive. We review the scope for improving the efficiency of the conventional helium recovery and upgrade processes, and evaluate the potential of emerging technologies based on adsorption or membrane separations for helium upgrade and purification. Helium recovery and purification processes are comparable in many ways with systems designed for hydrogen purification and thus, many of recent technological advances for H2 separation from CH4 N2 and CO2 may be applicable to a helium recovery process. Furthermore, some recent patents and pilot plant studies indicate there exist several opportunities for the development of advanced materials, such as helium-selective adsorbents, and optimized process operations for the recovery of helium from NG.

Synthesis and characterization of three amino-functionalized metal-organic frameworks based on the 2-aminoterephthalic ligand.

The incorporation of Lewis base sites and open metal cation sites into metal-organic frameworks (MOFs) is a potential route to improve selective CO2 adsorption from gas mixtures. In this study, three novel amino-functionalized metal-organic frameworks (MOFs): Mg-ABDC [Mg3(ABDC)3(DMF)4], Co-ABDC [Co3(ABDC)3(DMF)4] and Sr-ABDC [Sr(ABDC)(DMF)] (ABDC = 2-aminoterephthalate) were synthesized by solvothermal reactions of 2-aminoterephthalic acid (H2ABDC) with magnesium, cobalt and strontium metal centers, respectively. Single-crystal structure analysis showed that Mg-ABDC and Co-ABDC were isostructural compounds comprising two-dimensional layered structures. The Sr-ABDC contained a three-dimensional motif isostructural to its known Ca analogue. The amino-functionalized MOFs were characterized by powder X-ray diffraction, thermal gravimetric analysis and N2 sorption. The CO2 and N2 equilibrium adsorption capacities were measured at different temperatures (0 and 25 °C). The CO2/N2 selectivities of the MOFs were 396 on Mg-ABDC, 326 on Co-ABDC and 18 on Sr-ABDC. Both Mg-ABDC and Co-ABDC exhibit high heat of CO2 adsorption (>30 kJ mol(-1)). The Sr-ABDC displays good thermal stability but had a low adsorption capacity resulting from narrow pore apertures.

Structure Control of Nitrogen-Rich Graphene Nanosheets Using Hydrothermal Treatment and Formaldehyde Polymerization for Supercapacitors

Nitrogen-rich graphene nanosheets (NGN) with intentionally crumpled, stacked, and cross-linked sheet structures were developed using hydrothermal and/or formaldehyde polymerization processes. It is revealed that the hydrothermal treatment produced crumpled NGN (6.0 at% N) with a high surface area of 383 m(2)·g(-1). In contrast, the formaldehyde polymerization process yielded stacked NGN (11.3 at% N) with very low surface area. The combination of formaldehyde polymerization synthesis with hydrothermal treatment led to NGN (14.7 at% N) with a cross-linked structure and a moderate surface area of 88 m(2)·g(-1). Interestingly, this cross-linked NGN exhibited the best electrochemical performance compared with other NGN, with a remarkable specific capacitance of 201 F·g(-1) at 0.05 A·g(-1) in 1 M H2SO4 electrolyte, and an excellent retention rate of 96.2% of the initial capacitance after 10 000 charge-discharge cycles at a current density of 5 A·g(-1) was achieved.

Low‐Temperature Synthesis of Hierarchical Amorphous Basic Nickel Carbonate Particles for Water Oxidation Catalysis

Amorphous nickel carbonate particles are catalysts for the oxygen evolution reaction (OER), which plays a critical role in the electrochemical splitting of water. The amorphous nickel carbonate particles can be prepared at a temperature as low as 60 °C by an evaporation-induced precipitation (EIP) method. The products feature hierarchical pore structures. The mass-normalized activity of the catalysts, measured at an overpotential of 0.35 V, was 55.1 A g(-1) , with a Tafel slope of only 60 mV dec(-1) . This catalytic activity is superior to the performance of crystalline NiOx particles and β-Ni(OH)2 particles, and compares favorably to state-of-the-art RuO2 catalysts. The activity of the amorphous nickel carbonate is remarkably stable during a 10 000 s chronoamperometry test. Further optimization of synthesis parameters reveals that the amorphous structure can be tuned by adjusting the H2 O/Ni ratio in the precursor mixture. These results suggest the potential application of easily prepared hierarchical basic nickel carbonate particles as cheap and robust OER catalysts with high activity.

Gate opening effect of zeolitic imidazolate framework ZIF-7 for adsorption of CH4 and CO2 from N2

We report adsorption isotherms of CO2 and CH4 on the zeolitic imidazolate framework ZIF-7 that exhibit gate opening features associated with a flexible framework structure. This phenomenon has been reported by others for CO2 and light alkanes (e.g. ethane, ethylene, propane), but our study presents for first time experimental data to show that CH4 can also induce a gate opening effect in ZIF-7. Uptakes of CO2, CH4 and N2 on ZIF-7 were measured by a gravimetric adsorption apparatus at temperatures of 303–323 K and pressures up to 4494 kPa. From the CH4 isotherm measured at 303 K the transition pressure for the gate opening in ZIF-7 was estimated as 1245 kPa and the free-energy change associated with the structural phase change was 5.70 kJ mol−1. At an adsorption temperature of 303 K the phase transition pressure for CO2 in ZIF-F was 78 kPa and the free energy change was 2.43 kJ mol−1. The gate opening behaviour observed in this study shows ZIF-7 may have a potential selectivity for CH4 from N2 of more than 10 from an equimolar CH4 + N2 mixture. The equilibrium selectivity of ZIF-7 at 303 K and pressures close to 100 kPa are predicted to be 24 for CO2 from CH4 and 101 for CO2 from N2.

The effect of rank and lithotype on coal wettability and its application to coal relative permeability models

We report the effect of rank and lithotype on the wettability of artificial cleat channels in five coals from the Bowen Basin with ranks in the Rmax% range 0.98-1.91%. Wettability was assessed by measuring contact angles of air and water in the artificial cleats using a microfluidic Cleat Flow Cell (CFC) instrument. The artificial cleats were produced by reactive ion etching and had widths in the range 20-40 m that replicate the width and shape of some natural coal cleats under sub-surface reservoir conditions. These model cleats were developed to allow systematic laboratory investigations of water and gas relative permeability behaviour. Imbibition and drainage experiments were performed in the artificial channels using air and 0.1 %wt. fluorescein in fresh tap water to observe contact angles, the entry pressure of the air-water and water-air interface to the channel, and the pressure at which the channel was filled by the displacing fluid. Relative contact angles on the coal surface of 110 -140° were determined from images collected in the imbibition experiments. A trend of increasing contact angle with coal rank was observed. The low rank coal exhibited smaller contact angles and lower breakthrough pressures than the higher rank coal samples. In the drainage experiments the injection air displaced the water but left a residual liquid film on cleat walls across dull, inertinite rich bands. This residual film was not observed in the bright, vitrinite rich bands. The results of this study may provide the basis to consider an improved relative permeability model that explicitly accounts for wettability and the effect of coal rank.

Efficient water oxidation with amorphous transition metal boride catalysts synthesized by chemical reduction of metal nitrate salts at room temperature

We present a variety of amorphous transition-metal borides prepared at room temperature by a chemical reduction method as highly active catalysts for the oxygen evolution reaction (OER). The amorphous borides exhibit activities much higher than the corresponding crystalline (spinel, layered double hydroxide and perovskite) metal oxides containing the identical metal compositions, which have already been regarded as promising OER catalysts. The amorphous Ni/Fe borides showed the best mass normalized OER current density of 50 A g−1 at an overpotential of 0.35 V, transcending the performance of the state-of-the-art OER catalyst, RuO2. Amorphous transition-metal borides demonstrated extremely high active OER catalytic activity. The outstanding catalytic activity can be attributed to the amorphous structure, the large specific surface areas (above 110 m2 g−1) and the electron-enriched transition metal sites stemming from boron doping. The stoichiometry of the catalysts can be controlled precisely even for the synthesis of quaternary metal boride catalysts, which made it feasible to further optimize the catalytic activity. These results indicated that it is facile to prepare highly active OER catalysts by the one-step chemical reduction process at room temperature.