Pt foil

Mn(CH₃COO)₃-2H₂O (99%), Ni(CH₃COO)₂-4H₂O (99%), 1-octadecene (90%), myristic acid (99%), decanol (98%), MnO (99.99%), Mn₃O₄ (97%), Mn₂O₃ (99.9%), NaH₂PO₄-H₂O (99.0%, ACS reagent), and Na₂HPO₄-7H₂O (98.0–102.0%, ACS reagent) were purchased from Sigma Aldrich. Ni(NO₃)₂–6H₂O (99.9985%), MnO₂ (99.9%), and Pt foil (99.997%) were purchased from Alfa Aesar. Acetone (99.5%), toluene (99.5%), hexane (95%), cyclohexane (99.5%), and ethanol (99.5%) were purchased from Daejung Chemicals. All chemicals used as received without further purification. Fluorine doped tin oxide coated glass (FTO) with the surface resistivity of 8 Ω sq^–1 was obtained as 1.0 cm × 1.5 cm pre-cut glass pieces.

All electrochemical experiments were conducted under a three-electrode electrochemical cell system. A BASi Ag/AgCl/3M NaCl reference electrode and a Pt foil (2 cm × 2 cm × 0.1 mm, 99.997% purity, Alfa Aesar) were used as a reference electrode and a counter electrode, respectively. Electrochemical tests were carried out at ambient temperature (21 ± 1 °C) using a potentiostat system (CHI 600D, CH Instruments). Electrode potential was converted to the NHE scale, using the following equation: E(NHE) = E(Ag/AgCl) + 0.197 V. The electrolyte was phosphate buffer with 300 mM buffer strength under the pH 7.8.

The electrochemical
characterization of the membranes was investigated in a tailor-made
four-chamber (anode rinse, base, acid, and cathode rinse) flow cell
shown in Figure 2.
A 1 M NaOH solution was fed to the anode rinse chamber and base chamber
at 10 mL min^–1, and 1 M H₂SO₄ was fed to the cathode rinse chamber and acid chamber at 10 mL min^–1. Two pieces of Pt foil (99.99%, 0.001 in.-thick,
Alfa Aesar) supported on Ti plates were used as the working and counter
electrodes. The BPM was placed at the center of the cell with an AEM
(Neosepta AHA) and a CEM (Nafion NR-212) at each side to minimize
the influence of the electrode reaction on measurements. The effective
BPM area was defined using a 1.2 cm-diameter circular aperture. All
the measurements were conducted at room temperature.
The potential difference across
the membrane was measured by a
Hg/Hg₂SO₄ reference electrode [filled with saturated
K₂SO₄, E⁰ = 0.64
V vs normal hydrogen electrode (NHE) at 25 °C] in the acidic
chamber and a Hg/HgO reference electrode (filled with 1 M NaOH, E⁰ = 0.098 V vs NHE at 25 °C) in the alkaline
chamber. Chronopotentiometry and galvanostatic EIS of BPMs were conducted
at room temperature using a Gamry Reference 3000 potentiostat in a
standard four-electrode setup. In EIS measurements, an AC amplitude
of 10% of the applied DC current and a frequency spectrum from 300
kHz to 1 Hz was employed.