Ethanol Solvothermal Treatment on Graphitic Carbon Nitride Materials for Enhancing Photocatalytic Hydrogen Evolution Performance

Recently, Pt-loaded graphic carbon nitride (g-C3N4) materials have attracted great attention as a photocatalyst for hydrogen evolution from water. The simple surface modification of g-C3N4 by hydrothermal methods improves photocatalytic performance. In this study, ethanol is used as a solvothermal solvent to modify the surface properties of g-C3N4 for the first time. The g-C3N4 is thermally treated in ethanol at different temperatures (T = 140 °C, 160 °C, 180 °C, and 220 °C), and the Pt co-catalyst is subsequently deposited on the g-C3N4 via a photodeposition method. Elemental analysis and XPS O 1s data confirm that the ethanol solvothermal treatment increased the contents of the oxygen-containing functional groups on the g-C3N4 and were proportional to the treatment temperatures. However, the XPS Pt 4f data show that the Pt2+/Pt0 value for the Pt/g-C3N4 treated at ethanol solvothermal temperature of 160 °C (Pt/CN-160) is the highest at 7.03, implying the highest hydrogen production rate of Pt/CN-160 is at 492.3 μmol g−1 h−1 because the PtO phase is favorable for the water adsorption and hydrogen desorption in the hydrogen evolution process. In addition, the electrochemical impedance spectroscopy data and the photoluminescence spectra emission peak intensify reflect that the Pt/CN-160 had a more efficient charge separation process that also enhanced the photocatalytic activity.

Mutual Effects of Components of Protective Films Applied on Steel in Octadecylamine and 1,2,3-Benzotriazole Vapors

In this work, we used a combination of corrosion, electrochemical, and physical methods to determine the properties of nanoscale films obtained by treatment with octadecylamine (ODA), benzotriazole (BTA) vapors, and their mixtures at elevated temperatures. The mixture of ODA + BTA surpasses its components in protective aftereffect, but an analysis of their mutual effects shows that there is antagonism between them. Electrochemical impedance spectroscopy data indicate that the protection of steel by a mixture of ODA + BTA and its components is characterized by a mixed blocking activation mechanism. The processing of steel in hot vapors of the ODA + BTA mixture leads to hydrophobization of the surface and super-hydrophobization if a polymodal surface is created on the steel before processing in vapors.

Electrochemical Characterisations to Elucidate the Pseudocapacitance Mechanisms of a CdS/WOx Nanocomposite Photoanode in Acidic Aqueous Electrolytes

<p>The electrochemical properties of a cadmium sulphide/tungsten(VI) sub-oxide (CdS/WO_x) nanocomposite have been explored using aqueous solutions of acetic acid (pH 2.2) and acidified sodium acetate (pH 5.0), for the purpose of evaluating the origin of pseudocapacitance within the material. Through transient photocurrent response, galvanostatic charge/discharge and electrochemical impedance measurements, it was established that cation-intercalation phenomena were principally responsible for charge-accumulation in the composite and that the incorporation of ionic species into interstitial surface sites was more energetically favourable for protons than for sodium ions. The composite displayed promising capacitive performance in the tested electrolytes, exhibiting Coulombic efficiencies of up to 88% under galvanostatic cycling at 1.0 mA cm^-2 alongside a peak differential capacitance value of 560 mF cm^-2 during the discharge phase. From electrochemical impedance spectroscopy data it was further determined that whilst illumination by white light acted to decrease the series resistance of the photoanode, all other resistive and capacitive components of the impedance characteristics were affected negligibly by the irradiation. In combination, the investigations detailed herein provide an instructive resource for the development of CdS/WO_x composites and the optimisation of electrolytes to improve the performance and chemical stability of such materials. Furthermore, the study serves as a potential foundation from which to advance the concept of integrating the conversion and storage of solar energy into a single dual-functional electrode, in turn facilitating a new generation of photo-supercapacitor devices.</p>

Electrochemical Characterisations to Elucidate the Pseudocapacitance Mechanisms of a CdS/WOx Nanocomposite Photoanode in Acidic Aqueous Electrolytes

<p>The electrochemical properties of a cadmium sulphide/tungsten(VI) sub-oxide (CdS/WO_x) nanocomposite have been explored using aqueous solutions of acetic acid (pH 2.2) and acidified sodium acetate (pH 5.0), for the purpose of evaluating the origin of pseudocapacitance within the material. Through transient photocurrent response, galvanostatic charge/discharge and electrochemical impedance measurements, it was established that cation-intercalation phenomena were principally responsible for charge-accumulation in the composite and that the incorporation of ionic species into interstitial surface sites was more energetically favourable for protons than for sodium ions. The composite displayed promising capacitive performance in the tested electrolytes, exhibiting Coulombic efficiencies of up to 88% under galvanostatic cycling at 1.0 mA cm^-2 alongside a peak differential capacitance value of 560 mF cm^-2 during the discharge phase. From electrochemical impedance spectroscopy data it was further determined that whilst illumination by white light acted to decrease the series resistance of the photoanode, all other resistive and capacitive components of the impedance characteristics were affected negligibly by the irradiation. In combination, the investigations detailed herein provide an instructive resource for the development of CdS/WO_x composites and the optimisation of electrolytes to improve the performance and chemical stability of such materials. Furthermore, the study serves as a potential foundation from which to advance the concept of integrating the conversion and storage of solar energy into a single dual-functional electrode, in turn facilitating a new generation of photo-supercapacitor devices.</p>

Semiconductor-Ionic Nanocomposite La0.1Sr0.9MnO3−δ-Ce0.8Sm0.2O2−δ Functional Layer for High Performance Low Temperature SOFC

A novel composite was synthesized by mixing La0.1Sr0.9MnO3−δ (LSM) with Ce0.8Sm0.2O2−δ (SDC) for the functional layer of low temperature solid oxide fuel cell (LT-SOFC). Though LSM, a highly electronic conducting semiconductor, was used in the functional layer, the fuel cell device could reach OCVs higher than 1.0 V without short-circuit problem. A typical diode or rectification effect was observed when an external electric force was supplied on the device under fuel cell atmosphere, which indicated the existence of a junction that prevented the device from short-circuit problem. The optimum ratio of LSM:SDC = 1:2 was found for the LT-SOFC to reach the highest power density of 742 mW·cm−2 under 550 °C The electrochemical impedance spectroscopy data highlighted that introducing LSM into SDC electrolyte layer not only decreased charge-transfer resistances from 0.66 Ω·cm2 for SDC to 0.47–0.49 Ω·cm2 for LSM-SDC composite, but also decreased the activation energy of ionic conduction from 0.55 to 0.20 eV.