Activated carbons are prepared from raw hemp stem (hurd and bast) via hydrothermal processing and chemical activation. Both hemp bast and hemp hurd are converted into activated carbons of low-dimensional structures under certain experimental conditions. The experimental results show that hemp hurd is a better precursor than hemp bast for the preparation of activated carbons. The activated carbons are used to construct the electrodes of supercapacitor cells. The electrochemical performance of the activated carbons used in the supercapacitor cells is dependent on hydrothermal processing conditions and the mass ratio of KOH/biochar in the chemical activation. Excellent electrochemical performance metrics are achieved, including a specific capacitance of 160 F/g, and a high energy density of 19.8 Wh/kg at a power density of 21 kW/kg. Both the specific capacitance and capacitance retention increase with the increase of surface area and mesopore fraction. A simple relationship between the specific area capacitance and the fraction of micropores is proposed, via the rule of mixtures, and is supported by the experimental results. This relationship reveals the effect of the distribution of pore sizes on the specific area capacitance of electrochemical double layer capacitors.

The performance of carbon-supported cobalt catalysts was compared with that of Co/γ-Al2O3 reference catalysts for the Fischer–Tropsch synthesis (FTS) reaction. The carbon support (CS) was prepared using a hydrothermal method that formed mostly spherical ∼300–800 nm carbons that were first carbonized at 900 °C and then partially graphitized at 1900 °C. The FTS study was conducted using a continuously stirred tank reactor, and the cobalt catalysts were promoted with Pt (0.2% Pt–10% Co) to facilitate the reduction of cobalt oxides. Catalysts were prepared by an evaporative method (Co/CS-IWI) and by a chemical vapor deposition technique (Co/CS-CVD). The CVD technique led to a higher CO conversion (26.5%) relative to the conventional evaporative (IWI) method (7.4%) at the same temperature (220 °C) and space velocity (1.5 NL/gcath). Remarkably, the Co/CS-CVD displayed a high oxygenate selectivity (∼10%) in comparison with cobalt alumina catalysts (i.e., including one having similar Pt and Co loadings, as well as a conventional cobalt alumina catalyst with a higher Co loading of 25% Co) at similar conversion levels. The difference in the CO conversion on a per gram catalyst basis observed between Co/CS-IWI and Co/CS-CVD catalysts was due to the smaller average Co particle size and more uniform distribution resulting from the CVD method.

Knowledge of the carrier type (p- or n-type) and the carrier density of carbon nanotubes is critical in semiconductor applications such as thermoelectric power generation and Peltier cooling. In this paper, an experimental procedure for electrochemically characterizing multiwalled carbon nanotubes (MWCNTs) doped with boron or nitrogen has been presented. The carrier type and carrier density of the doped MWCNTs were determined by generating Mott–Schottky plots. The boron-doped nanotubes were synthesized using the substitution reaction method and the nitrogen-doped MWCNTs were synthesized using the continuous-feed chemical vapor deposition (CVD) method using pyridine or acetonitrile as the carbon precursor and ferrocene as the metal catalyst particle precursor. The nitrogen-doped nanotubes were synthesized at different CVD reaction temperatures: 650, 700, 800, and 900°C , and the effect of reaction temperature on the carrier densities of the carbon nanotubes was examined. Thermoelectric devices were constructed using pyridine nanotubes synthesized at different synthesis temperatures, and it was found that with any change (increase/decrease) in the carrier densities reflected a corresponding change in the thermoelectric power of the nanotubes.

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The electrochemical behavior of carbon fiber epoxy matrix electrodes has been tested. A simple outer‐sphere redox couple was used as the test reaction. The results indicate no dependence on fiber orientation (random, parallel, or perpendicular). Rate constants are not significantly different from those observed for the same reaction on Pt electrodes, indicating that the catalytic activity plays little or no role in determining the kinetics of this reaction. Chronoamperometric measurements at short times, in the millisecond range, reveal the unique features of composite electrodes as ensembles of microelectrodes.