No abstract

The dissociation of methane in the intense laser field has been investigated experimentally and theoretically. Using an amplified ultrafast Ti:sapphire laser around 800 nm coupled to a TOF mass spectrometer, all the primary and secondary ions were produced and detected at the laser intensities 10 13 to 10 14 W/cm 2 . The experimental results show that the dissociation of methane proceeds via a stepwise mechanism by gradually increasing the laser intensity. The maximum H + yield is formed when the linearly polarized laser field is parallel to the axis of the TOF tube. A quasi-diatomic theoretical model has been proposed and used to interpret the dissociation of polyatomic molecules. The model assumes that only the dissociative bond is considered and the rest of the molecular geometry is fixed during the dissociation. For each step, the profiles of the dressed potential energy surfaces (PESs) along the dissociative bond of the molecule at different laser intensities are calculated. Quasi-classical trajectories on the dressed PESs are calculated, showing that the wave packet is modulated by the sinusoidal laser field. Theoretical dissociation probabilities are thus calculated. The results can fully interpret the overall dissociation processes and the angular dependence of H + yield.

The development of sustainable and renewable energy storage systems is a promising approach toward steady and reliable energy supply. In this study, cellulosic palm loofah fibers were used as a precursor to produce amorphous carbon (Am-C) with retained crystalline cellulosic planes via a simple activation method. The Am-C exhibits a fairly high BET surface area of 2000 m2/g and a 3D-microporous structure with small mesopores. The symmetric Am-C//Am-C supercapacitor device tested in 1.0 M NaCl aqueous electrolyte showed specific capacitances of 201 F/g at 5 mV/s and 337 F/g at 1 A/g. The device exhibits a stable performance across a potential window of 1.8 V with ultrahigh energy and power densities of 51.4 Wh/kg at 4.5 kW/kg and 16.95 Wh/kg at 18 kW/kg. The device showed extraordinary increasing capacitive behavior upon cycling at 10 A/g for over 25000 cycles. The exceptional device performance could be ascribed to the electrochemical graphitization during long-term cycling together with the enhanced wettability as confirmed via Raman, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and contact angle measurements.

This study addresses the enhancement of the oxygen evolution reaction (OER) on glassy carbon, Au, and Pt electrodes modified with binary catalysts composed of nickel oxide nanoparticles (nano-NiO x ) and cobalt oxide nanoparticles (nano-CoO x ). Binary NiO x /CoO x -modified electrodes (with NiO x initially deposited) show a high catalytic activity and a marked stability which far exceeds that obtained at the individual oxide-modified electrodes. This enhancement is demonstrated by a marked negative shift (more than ca. 600 mV) in the onset potential of the OER compared to that obtained at the unmodified electrodes. The modified electrodes show a significantly higher long-term stability, over a period of 5 h of continuous electrolysis, without any significant loss of activity towards the OER in alkaline medium. The influence of the solution pH, the loading level, and sequence of deposition of each oxide on the electrocatalytic activity of the modified electrodes is addressed with an aim to maximize the catalytic activity of the modified electrodes towards the OER. SEM imaging is used to disclose the size and morphology of the fabricated nano-NiO x and nano-CoO x binary catalysts at the electrode surface.

The dissociation of acetone in an intense (10 13 -10 14 W/cm 2 ) femtosecond laser field has been investigated. The stepwise nature of the dissociation has been verified by analyzing the time-of-flight mass spectroscopic patterns at different laser intensities. The stepwise nature was interpreted using a quasi-diatomic field-assisted dissociation model and the QCT calculations. Both the experimental identification and the theoretical predictions show that if the laser