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Abstract: IrO2 electrocatalysts were prepared and electrochemically characterized for the oxygen evolution reaction in a Solid Polymer Electrolyte (SPE) electrolyzer. By using a sulfite complex-based preparation procedure, an amorphous iridium oxide precursor was obtained at 80 °C, which was, successively, calcined at different temperatures: 350 °C, 400 °C and 450 °C. A physico-chemical characterization was carried out by X Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray-photoelectron spectroscopy (XPS). The various IrO2 catalysts were sprayed onto a Nafion 115 membrane with a loading of 2.5 mg cm−2 to form the anode. A Pt/C catalyst (Pt loading 0.5 mg cm−2) was used as cathode. The best electrochemical performance was obtained for the cell based on the IrO2 calcined at 350 °C. The maximum current density at high potentials (1.8  V) was about 1.75 A cm−2. Accelerated time-tests at 2 A cm−2 demonstrated a suitable stability of the IrO2 calcined at 350 °C; however, the intrinsic stability appeared to increase with the calcination temperature. The sample calcined at 400 °C could represent a good compromise between performance and intrinsic stability. [Copyright &y& Elsevier]

Abstract: An optimization study of components and assembling characteristics for a proton exchange membrane (PEM) short stack electrolyzer (3 cells of 100 cm2 geometrical area) was carried out. The electrochemical properties were investigated by polarization, impedance spectroscopy and chrono-potentiometric measurements. A decrease of the ohmic contact resistance between the bipolar plates and the electrode backing layer was obtained by using an appropriate thickness for the gas diffusion layers/current collectors as well as by an optimization of stack compression. The amount of H2 produced was ∼90 l h−1 at 60 A (600 mA cm−2) and 75 °C under 300 W of applied electrical power. No significant leakage or gas recombination was observed. The stack electrical efficiency was 75% and 88%, at 60 A and 75 °C, with respect to the low and high heating value of hydrogen, respectively. [Copyright &y& Elsevier]

Abstract: A nanosized IrO2 anode electrocatalyst was prepared by a sulfite-complex route for application in a proton exchange membrane (PEM) water electrolyzer. The physico-chemical properties of the IrO2 catalyst were studied by termogravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The electrochemical activity of this catalyst for oxygen evolution was investigated in a single cell PEM electrolyzer consisting of a Pt/C cathode and a Nafion® membrane. A current density of 1.26Acm−2 was obtained at 1.8V and a stable behavior during steady-state operation at 80°C was recorded. The Tafel plots for the overall electrochemical process indicated a slope of about 80mVdec−1 in a temperature range from 25°C to 80°C. The kinetic and ohmic activation energies for the electrochemical process were 70.46kJmol−1 and 13.45kJmol−1, respectively. A short stack (3 cells of 100cm2 geometrical area) PEM electrolyzer was investigated by linear voltammetry, impedance spectroscopy and chrono-amperometric measurements. The amount of H2 produced was 80lh−1 at 60A under 330W of applied electrical power. The stack electrical efficiency at 60A and 75°C was 70% and 81% with respect to the low and high heating value of hydrogen, respectively. [Copyright &y& Elsevier]