A systematic comparative study of the efficient co-catalyst-free photocatalytic hydrogen evolution by transition metal oxide nanofibers

The efficiencies of a series of hydrogen evolving catalysts based on metal oxide nanofibers (NiO, Co₃O₄, Mn₃O₄) are investigated for the photocatalytic hydrogen evolution from water without using any co-catalyst under the visible light irradiation by using triethanolamine (TEOA) as an electron donor and Eosin-Y (EY) dye as a photosensitizer. It is found that the photocatalytic hydrogen evolution activities follow the order as: Mn₃O₄<Co₃O₄<NiO (196 μmolg^?1h^?1, 5552 μmolg^?1h^?1, 7757 μmolg^?1h^?1, respectively). Moreover, the catalytic behavior of these nanofibers on the hydrogen production has been also compared to bulk forms of NiO, Co₃O₄ and Mn₃O₄ by producing hydrogen 937 μmolg^?1h^?1, 901 μmolg^?1h^?1 and 135 μmolg^?1h^?1, respectively. The nanofiber structures demonstrated much higher photocatalytic activity than bulk forms due to the effect of the increased surface to volume ratio deduced from the fibrous character. The photocatalytic plausible pathway for the hydrogen production is also discussed.     

Mechanical behavior and microhardness of swollen natural rubber loaded with carbon black

The mechanical behavior and microhardness characteristics of a natural rubber vulcanizate loaded with 40 phr high abrasion furnace carbon black swollen in kerosene were studied. The measured parameters (i.e., the Young's modulus, tensile strength, and elongation at break) varied with the swelling time in kerosene. The hardness degree decreased as the swelling time in kerosene increased. Different models were applied to describe this mechanical behavior. The Mooney–Rivilin relation agreed with the experimental data at low extension ratios, whereas the Blatz relation agreed at high extension ratios only. The strain rate sensitivity was taken into account to describe this mechanical behavior. The strain energy density as a function of the swelling time in kerosene was calculated with three different equations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Enhanced Bio-Electrochemical Reduction of Carbon Dioxide by Using Neutral Red as a Redox Mediator

Microbial electrosynthetic cells containing Methylobacterium extorquens were studied for the reduction of CO₂ to formate by direct electron injection and redox mediator-assisted approaches, with CO₂ as the sole carbon source. The formation of a biofilm on a carbon felt (CF) electrode was achieved while applying a constant potential of −0.75 V versus Ag/AgCl under CO₂-saturated conditions. During the biofilm growth period, continuous H₂ evolution was observed. The long-term performance for CO₂ reduction of the biofilm with and without neutral red as a redox mediator was studied by an applied potential of −0.75 V versus Ag/AgCl. The neutral red was introduced into the systems in two different ways: homogeneous (dissolved in solution) and heterogeneous (electropolymerized onto the working electrode). The heterogeneous approach was investigated in the microbial system, for the first time, where the CF working electrode was coated with poly(neutral red) by the oxidative electropolymerization thereof. The formation of poly(neutral red) was characterized by spectroscopic techniques. During long-term electrolysis up to 17 weeks, the formation of formate was observed continuously with an average Faradaic efficiency of 4 %. With the contribution of neutral red, higher formate accumulation was observed. Moreover, the microbial electrosynthetic cell was characterized by means of electrochemical impedance spectroscopy to obtain more information on the CO₂ reduction mechanism.     

Metal-Free Hydrogen-Bonded Polymers Mimic Noble Metal Electrocatalysts

The most active and efficient catalysts for the electrochemical hydrogen evolution reaction (HER) rely on platinum, a fact that increases the cost of producing hydrogen and thereby limits the widespread adoption of this fuel. Here, a metal-free organic electrocatalyst that mimics the platinum surface by implementing a high work function and incorporating hydrogen-affine hydrogen bonds is introduced. These motifs, inspired from enzymology, are deployed here as selective reaction centres. It is shown that the keto-amine hydrogen-bond motif enhances the rate-determining step in proton reduction to molecular hydrogen. The keto-amine-functionalized polymers reported herein evolve hydrogen at an overpotential of 190 mV. They share certain key properties with platinum: a similar work function and excellent electrochemical stability and chemical robustness. These properties allow the demonstration of one week of continuous HER operation without notable degradation nor delamination from the carrier electrode. Scaled continuous-flow electrolysis is reported and 1 L net molecular hydrogen is produced within less than 9 h using 2.3 mg of polymer electrocatalyst.     

Calculation of neutral fraction for ion neutralization at metal surfaces by bulk-plasmon excitation

The excitation of bulk plasmons during the neutralization of protons scattered from metal surfaces was analyzed theoretically in previous work. Also, experimental evidence for this mechanism is now discussed in the literature. In this work the neutral fraction generated by this mechanism is calculated. The calculation for the neutral fraction in the scattering of protons from aluminum surface shows that it is quite small compared to that for surface-plasmon-assisted neutralization. The characteristic velocity for bulk-plasmons-assisted neutralization is 0.0009 (in atomic units). Its value for surface-plasmon-assisted neutralization is 0.75. It is concluded that, within the assumption of our theory that there is no penetration of protons into the surface (implying low-energy protons), the mechanism of surface-plasmons-assisted neutralization would be expected to be more important than that of bulk-plasmon-assisted neutralization.     

Energy-Efficient Minimum Mobile Charger Coverage for Wireless Sensor Networks

Journal of Computer Science and Technology - Sustaining an operational wireless sensor network (WSN) is challenging due to the persistent need of the battery-powered sensors to be charged from time...