Electrocatalysis of carbon black- or activated carbon nanotubes-supported Pd–Ag towards methanol oxidation in alkaline media

Carbon black supported bimetallic palladium–silver (Pd–Ag/C) catalysts with different Ag loadings were prepared by borohydride reduction of mixed metal salts and carbon support. Electrochemical activities of these catalysts towards methanol oxidation in alkaline media were examined and the Pd–Ag(1:1)/C catalyst (onset potential of −0.59 V) shows better catalytic activity than the Pd/C catalyst (onset potential of −0.49 V). The addition of Ag also facilitates methanol oxidation and removal of the adsorbed CO. The synthesized activated carbon nanotubes (CNTs)-supported Pd–Ag(1:1) catalyst exhibits even better catalytic activity contributed from larger electroactive surface area and better intrinsic catalytic activity than the carbon black supported bimetallic palladium–silver (Pd–Ag/C) catalyst.     

Vertically aligned carbon nanotube – Polyaniline nanocomposite supercapacitor electrodes

We develop a fast and cost effective method for the fabrication of a nanocomposite supercapacitor electrode. In this study aluminum foils were decorated with vertically aligned carbon nanotubes (VACNT) via chemical vapor deposition (CVD) method, which was followed by the electrodeposition of polyaniline (PANI) layer on top of the VACNTs. Electrochemical behavior of the fabricated nanocomposite electrodes were evaluated through cyclic voltammetry, galvanostatic charge discharge cycles and electrochemical impedance spectroscopy method. Fabricated VACNT/PANI nanocomposite electrodes through 15 electrodeposition cycles showed significant electrochemical performance. The specific capacity of these electrodes was calculated as 16.17 mF/cm² at a current density of 0.25 mA/cm².     

Lost carbon emissions: the role of non-manufacturing “other industries” and refining in industrial energy use and carbon emissions in IEA countries

We present a review of trends in energy use and output in branches of industry not often studied in detail: petroleum refining and what we call the other industries — agriculture, mining, and construction. From a sample of IEA countries we analyze eight with the most complete data from the early 1970s to the mid-1990s. We carry out a decomposition analysis of changes in energy use and carbon emissions in the “other industries” sector. We also review briefly the impact of including refining in the evolution of manufacturing energy use, usually studied without refining. Despite many data problems, we present our results as a way of enticing others to study these important “lost” sectors more carefully. We have five basic findings. First, “other industries” tends to be a minor consumer of energy in many countries, but in some, particularly Denmark, the US, and Australia, mining or agriculture can be a major sector too large to be overlooked. Second, refining is an extremely energy intensive industry which despite a relatively low share of value added consumes as much as 20% of final energy use in manufacturing. Third, as a result of a slower decline in the carbon-intensity of these industries vis-à-vis the manufacturing industries, their share of industrial emissions has been rising. Fourth, for other industries variation in per capita output plays a relatively small role in differentiating per capita carbon emissions compared to the impact of subsectoral energy intensities. Finally, including this energy in CO₂ calculations has little impact on overall trends, but does change the magnitude of emissions in most countries significantly. Clearly, these industries provide important opportunities for searching for carbon emissions reductions.     

Opposite effects of self-growth amorphous carbon and carbon nanotubes on the reforming of toluene with Ni/α-Al2O3 for hydrogen production

Ni-based catalysts are prone to be deactivated by carbon deposition. This study aims to investigate the influence mechanism of different types of carbon deposition on the activity of Ni/α-Al₂O₃ catalyst at various steam-to-carbon (S/C) ratios during steam reforming of toluene for hydrogen production. At a low S/C ratio of 1, the catalytic activity of Ni/α-Al₂O₃ was inhibited due to the covering and blocking of Ni active sites by the formation of amorphous carbon on the Ni surface. While at a high S/C ratio of 3, more than 80 wt% of carbon deposition was found to be self-growth carbon nanotubes (CNTs) with an average diameter of around 15 nm. The activity of Ni/α-Al₂O₃ in steam reforming of toluene was unusually promoted, which can be attributed to the tip-growth mechanism of CNTs, whereby the Ni particles migrated to the tip or the surface of CNTs, resulting in the improved active site dispersion.     

A methanol – Tolerant carbon supported Pt–Sn cathode catalysts

Carbon supported Pt–Sn bimetallic electrocatalysts with a Pt:Sn 90:10 atomic ratio were prepared by impregnation method and then heat treated at 300 and 500 °C under Helium atmosphere. The purpose of this work is to investigate the effect of tin addition to platinum for methanol tolerant oxygen reduction reaction. In this sense, structure and morphological properties of supported bimetallic catalysts were correlated to the catalytic performance. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterizations confirm the formation of Pt–Sn bimetallic electrocatalysts with a Pt single-phase material alloy and revealed an increase in the average particle size after heat treatment. The electrocatalytic activities of these samples for the oxygen reduction reaction (ORR) were examined in acidic medium using both a rotating disk (RDE) and a rotating ring disk (RRDE) electrodes. Compared with the Pt/C, Pt–Sn/C bimetallic catalysts show superior electrocatalytic activity towards ORR with an approaching four electron pathway leading to water formation. The specific and mass activity for ORR follow the order of Pt–Sn/C-500 ≈ Pt–Sn/C-300 > Pt–Sn/C > Pt/C. Furthermore, it is found that among the three Pt–Sn samples, Pt–Sn/C-500 exhibits the highest methanol tolerance. These experimental observations indicate that the addition of Sn into Pt is favorable to maximize the ORR performances of platinum and further the heat treatment is beneficial to improve the methanol tolerance behavior. On this basis, the novel Pt–Sn catalysts can be considered as potential candidates to be used as cathodes in Direct Methanol Fuel Cells.     

Multiple bed regenerative adsorption cycle using the monolithic carbon–ammonia pair

A refrigeration/heat-pump system based on a number of simple tubular adsorption modules is described. A single module is comprised of a generator and a receiver/condenser/evaporator. A single generator consisting of a 12.7 mm stainless steel tube lined with 2.6 mm of monolithic active carbon has been manufactured. A complete module has been tested in a simple rig, which subjects it to alternating hot and cold airstreams, desorbing and adsorbing ammonia. A complete system, consisting of 32 modules has been modelled in detail and its predicted performance is presented. Key parameters have been varied and their effect on the performance discussed.     

High-performance and stable La0.8Sr0.2Fe0.9Nb0.1O3-δanode for direct carbon solid oxide fuel cells fueled by activated carbon and corn straw derived carbon

The novel perovskite La_0.8Sr_0.2Fe_0.9Nb_0.1O_3-δ (LSFNb) anode for direct carbon-solid oxide fuel cells (DC-SOFCs) is evaluated using activated carbon and corn straw carbon as fuels. Activated carbon possesses less ratio of disorder carbon, smaller average particle size and much higher specific surface area, as well as porous structure with micropores and mesopores compared with corn straw carbon. Electrolyte-supported DC-SOFCs with LSFNb anode demonstrate excellent performance with peak power densities of 302.8 mW cm^?2 and 218.5 mW cm^?2, respectively, when operated with activated carbon and corn straw carbon at 850 °C. Polarization resistances of LSFNb anode indicate that performance of DC-SOFCs is largely determined by the reverse Boudouard reaction, which is related to specific surface area of fuels. Cells fueled by corn straw carbon exhibit more stable output, higher released electric quantity and higher fuel utilization rate than that using activated carbon. Despite more disorder carbon and better thermal reactivity of corn straw carbon, higher initial output performance is obtained with activated carbon, proving that specific surface area of fuels, particle size and porosity have a considerable influence on the reverse Boudouard reaction and cell performance. These results indicate that LSFNb is a promising perovskite anode material for DC-SOFC.     

Development of adsorption air-conditioning technology using modified activated carbon – A review

Adsorption air-conditioning technology has attracted much attention recently due to its environmental friendly property. Some successes have been reported in the literature on the adsorption technology for air-conditioning applications. This paper presents an overview of the researches which had been carried out on adsorption refrigeration system with the commonly used adsorbent and adsorbate working pairs, solar adsorption refrigeration and adsorption technologies in automobile. Activated carbon has been widely used as the adsorbent in adsorption refrigeration system. However, one of the bottlenecks which prevent the improvement of the adsorption refrigeration technology using activated carbon is the use of the readily available commercial activated carbon without prior treatment, which has resulted in relatively lower performance as compared to the conventional absorption and vapour compression technologies. Various modification methods on activated carbon are thus discussed in this paper for future development and improvement of adsorption air-conditioning system.     

Price drivers and structural breaks in European carbon prices 2005–2007

This article aims at characterizing the daily price fundamentals of European Union Allowances (EUAs) traded since 2005 as part of the Emissions Trading Scheme (ETS). The presence of two structural changes on April 2006 following the disclosure of 2005 verified emissions and on October 2006 following the European Commission announcement of stricter Phase II allocation allows to isolate distinct fundamentals evolving overtime. The results extend previous literature by showing that EUA spot prices react not only to energy prices with forecast errors, but also to unanticipated temperatures changes during colder events. Besides, the sub-period decomposition of the pilot phase gives a better grasp of institutional and market events that drive allowance price changes.     

Advanced solid sorption air conditioning modules using monolithic carbon–ammonia pair

In order to design and build a low cost rotary regenerative adsorption air conditioning system using monolithic carbon–ammonia in a multiple bed design, three single module configurations have been tested. The basic single module named MODULAR1-0.0 consists of stainless steel tube 12.7 mm in diameter, wall thickness 0.25 mm and 600 mm long and contains about 2.6 mm layer of monolithic carbon (about 40 g) from WaterLink Sutcliffe Carbons Ltd. The far end of the module (about 230 mm long) is the evaporator–condenser (receiver). An inert material (PTFE) is inserted between the receiver and the generator as an adiabatic section that reduces the longitudinal conduction between them. From the basic module, two other module configurations (MODULAR2-0.125 and MODULAR2-0.3) are considered with external aluminium fins to improve the heat transfer capacity of the module: each consists of two basic single modules with both generator and receiver fitted with rectangular aluminium fins. This paper is focused on detailed design, construction and testing of modules. The experimental results are presented and discussed. At typical conditions (T_G=100 °C, T_C=30 °C and −5 °C<T_E<20 °C), MODULAR2-0.125 has provided the best performance with a maximum specific cooling of about 0.600 kW kg⁻¹ carbon which is 30% and 60% better than the performance of MODULAR2-0.3 and 2-MODULAR1-0.0 respectively. The typical COP of each module is about 0.20 without regeneration and about 0.50 with regeneration.     

Electrochemical characterization of activated carbon–ruthenium oxide nanoparticles composites for supercapacitors

The high specific capacitance of ruthenium oxide (denoted as RuO_x) nanoparticles prepared by a modified sol–gel method with annealing in air for supercapacitors was demonstrated in this work. The specific capacitance of activated carbon (denoted as AC) measured at 5 mA/cm² is significantly increased from 26.8 to 38.7 F/g by the adsorption of RuO_x nanoparticles with ultrasonic weltering in 1 M NaOH for 30 min. This method is a promising tool in improving the performance of carbon-based double-layer capacitors. The total specific capacitance of a composite composed of 90 wt.% AC and 10 wt.% RuO_x measured at 25 mV/s is about 62.8 F/g, which is increased up to ca. 111.7 F/g when RuO_x has been previously annealed in air at 200 °C for 2 h. The specific capacitance of RuO_x nanoparticles was promoted from 470 to 980 F/g by annealing in air at 200 °C for 2 h. The nanostructure of RuO_x was examined from the transmission electron microscopic (TEM) morphology.     

Integrated carbon composite bipolar plate for polymer–electrolyte membrane fuel cells

The electrical resistance of bipolar plates for polymer–electrolyte membrane fuel cells (PEMFCs) should be very low to conduct the electricity generated with minimum electrical loss. The resistance of a bipolar plate consists of the bulk material resistance and the interfacial contact resistance when two such plates are contacted to provide channels for fuel and air (oxygen) supplies.     

Aligned carbon nanotube–Pt composite fuel cell catalyst by template electrodeposition

Solution phase deposition of aligned arrays of carbon nanotubes (CNTs) in a platinum (Pt) matrix composite is demonstrated. The catalyst material is electrodeposited in an oriented manner on the nanoscale using anodised aluminium oxide (AAO) templates. The catalyst performance of the composite for the oxidation of methanol is shown. The carbon monoxide (CO) tolerance is increased and the catalyst function is improved by minimising the influence of adsorbed CO on the kinetics of the methanol oxidation reaction.     

Graphite–carbon nanotube composite electrodes for all vanadium redox flow battery

The voltammetric behaviors of graphite (GP) and its composites with carbon nanotube (CNT) were studied in 5 M H₂SO₄ + 1 M VOSO₄ solution with cyclic voltammetry (CV), and the surface morphology of the composites was observed with scanning electron microscope (SEM). The results obtained from voltammetry show that the redox couples of V(IV)/V(V) and V(II)/V(III), as positive and negative electrodes of all vanadium flow liquid battery, respectively, have good reversibility but low current on the GP electrode, and the current can be improved by CNT. It is found from the observation of SEM that the CNT is dispersed evenly on the surface of sheet GP when they are mixed together. The best composition for the positive and the negative of all vanadium flow liquid battery determined by comparing voltammetric behavior of the composite electrodes with different content of CNT is 5:95 (w_CNT/w_GP) for both positive and negative electrodes. The activity of the composite electrode can be affected by the heat treatment of CNT. CNT treated at 200 °C gives better activity to the composite electrode.     

Charge–discharge properties of surface-modified carbon by resin coating in Li-ion battery

The effect of an epoxy resin coating on the electrochemical performance of Li-ion batteries is investigated. Mesocarbon microbeads (MCMB), which constitute a promising carbon anode material for rechargeable Li-ion batteries is used as a starting carbon material. The surface coating of the MCMB is carried out by refluxing in a dilute H₂SO₄ solution and mixing in the epoxy resin-dissolved tetrahydrofuran (THF) solution. After heat treatment at 1000–1300 °C, the resin coating layer on the MCMB is converted to an amorphous phase which is identified by means of a high resolution transmission electron microscope (HRTEM) and a electron energy loss spectroscopy (EELS) analyses. The Brunauer–Emmett–Teller (BET) surface area of MCMB is increased by the formation of the amorphous epoxy resin coating layer. The electrochemical performance of the MCMB, such as the charge–discharge capacity and cycleability, is enhanced by the surface modification through epoxy resin coating. The reasons for the improvement of electrochemical performance are discussed in terms of the results from HRTEM observation, EELS analysis, and cyclicvoltammetry     

Hydrogen and carbon dioxide as raw materials for an ecological energy—technology

The Fachhochschule Wiesbaden has developed and operated two decentral energy-systems of hydrogen-technology where the hydrogen serves as storage-medium for solar and wind-energy. The principal economical results are described. It is evident that the hydrogen-price is too high for energy-technology. One of the reasons is the high storage-price for pressurized hydrogen. A price-reduction is possible if also the electrolytical oxygen is used, for instance in a waste-water purification plant. The storage problem can be solved if one lets react the hydrogen with carbon dioxide. The reaction product is methanol, a liquid energy-carrier for which exists the distribution infrastructure. The principles of this energy-technology (to store energy by reaction-products of hydrogen and carbon-dioxide) are known, because nature has applied it for millions of years in plants. But a lot of details have to be developed. The introduction of this new technology requires considerable efforts in the development of procedures, catalysts, apparatus, materials. There are many possibilities to solve the problem; the optimized one has to be found.