Role of CO in the Water-Induced Formation of Cobalt Oxide in a High Conversion Fischer–Tropsch Environment

A Co/C model catalyst was exposed to increasing partial pressures of water simulating high Fischer–Tropsch conversions at varying concentrations of synthesis gas. The stability of the metallic cobalt phase against oxidation and sintering under such conditions was monitored in an <i>in situ</i> magnetometer. Direct oxidation of cobalt to cobalt oxide with water-derived oxygen through a water splitting mechanism was shown to be kinetically hindered, even at high partial pressures of water. Combined threshold partial pressures of carbon monoxide and water were identified for rapid oxidation of cobalt, above which the removal of adsorbed oxygen species, originating from the dissociation of carbon monoxide on the metallic cobalt surface, by surface produced water was hindered resulting in water-induced oxidation

Enhanced Electrochemical Behavior of Peanut-Shell Activated Carbon/Molybdenum Oxide/Molybdenum Carbide Ternary Composites

Biomass-waste activated carbon/molybdenum oxide/molybdenum carbide ternary composites are prepared using a facile in-situ pyrolysis process in argon ambient with varying mass ratios of ammonium molybdate tetrahydrate to porous peanut shell activated carbon (PAC). The formation of MoO2 and Mo2C nanostructures embedded in the porous carbon framework is confirmed by extensive structural characterization and elemental mapping analysis. The best composite when used as electrodes in a symmetric supercapacitor (PAC/MoO2/Mo2C-1//PAC/MoO2/Mo2C-1) exhibited a good cell capacitance of 115 F g−1 with an associated high specific energy of 51.8 W h kg−1, as well as a specific power of 0.9 kW kg−1 at a cell voltage of 1.8 V at 1 A g−1. Increasing the specific current to 20 A g−1 still showcased a device capable of delivering up to 30 W h kg−1 specific energy and 18 kW kg−1 of specific power. Additionally, with a great cycling stability, a 99.8% coulombic efficiency and capacitance retention of ~83% were recorded for over 25,000 galvanostatic charge-discharge cycles at 10 A g−1. The voltage holding test after a 160 h floating time resulted in increase of the specific capacitance from 74.7 to 90 F g−1 at 10 A g−1 for this storage device. The remarkable electrochemical performance is based on the synergistic effect of metal oxide/metal carbide (MoO2/Mo2C) with the interconnected porous carbon. The PAC/MoO2/Mo2C ternary composites highlight promising Mo-based electrode materials suitable for high-performance energy storage. Explicitly, this work also demonstrates a simple and sustainable approach to enhance the electrochemical performance of porous carbon materials

Nitridation temperature effect on carbon vanadium oxynitrides for a symmetric supercapacitor

Please read abstract in article.(SARChI) of the Department of Science and Technology and National Research Foundation (NRF) of South Africa.http://www.mdpi.com/journal/nanomaterialspm2020Physic

Valorization of biodigestor plant waste in electrodes for supercapacitors and microbial fuel cells

This study aims at demonstrating that wastes from anaerobic biodigester plants can be effectively valorized as functional materials to be implemented in technologies that enable efficient energy management and water treatment, therefore simultaneously addressing the Water-Energy-Waste Nexus challenges. Lignin, the main solid residue of the biodigester plant, has been valorized into activated biochar with a mild activation agent, like KHCO3, to produce electrode of supercapacitors and microbial fuel cells. In addition, the same sludge that is the liquid effluent of the biodigester plant has been exploited as inoculum and electrolyte for the MFC. The lignin-derived carbons obtained at lignin/KHCO3 mass ratios of 1:0.5 (LAC-0.5) and 1:2 (LAC-2) comprised of mesopores and micropores displaying BETs of 1558 m2g 121 and 1879 m2g 121, respectively. LAC-2 carbon exhibited a superior specific capacitance of 114 F g 121 in 2.5 M KNO3 with respect to LAC-0.5. A supercapacitor with LAC-2 electrodes was built displaying specific energy specific power up to 10 Wh kg 121 and 6.9 kW kg 121, respectively. Durability tests showed that the device was able to maintain a capacitance retention of 84.5% after 15,000 charge-discharge cycles. The ligninderived carbons were also studied as electrocatalysts for ORR in a neutral medium. The LAC-2 showed higher ORR electrocatalytic activity than LAC-0.5. The interconnected porous network and the high surface area made the lignin-derived porous carbons suitable electrode materials for dual applications. The feasibility of the use of LAC 2 carbon incorporated in an air breathing cathode for MFC applications is also reporte