Perchloric acid hclo4

All of the chemicals are of analytical grade and used without further purification. Commercial references of Vulcan carbon-supported Pt electrocatalyst (50 wt%, TEC-10E50E) was purchased from TKK, Japan. Other reagents are as follows: isopropanol (IPA, >99.9%, analytical reagent grade, Kermel), Nafion D521 dispersion (5 wt%, EW = 1100, Ion Solution Inc), potassium tetrachloroplatinate (K₂PtCl₄, 98%, RHAWN), nickel dichloride (NiCl₂, 99%, RHAWN), sulfuric acid (H₂SO₄, 95–98 wt%, analytical reagent grade, SCR, China), perchloric acid (HClO4, 70%, Sigma Aldrich). Argon and oxygen gases having high purity (>99.99%) were purchased from Yihong Gas Company, China. Deionized water (20 ± 1°C, pH 7, ρ = 18.3 MΩ/cm) was purified by passing through pure compact ultrapure water system (Arium mini, Sartorius).

For ¹H-NMR, a solution was prepared (6% (w/w)) of MeHA polymer in D₂O and analyzed on a 300 mHz Gemini Spectrometer (Varian, Palo Alto, CA). All samples were measured with a relaxation delay of 0.6 seconds for 512 scans. The degree of methacrylate substitution was calculated by comparing the integrals of the peaks of the methacrylate groups at 1.9, 5.7 and 6.1 ppm relative to the integrals originating from the protons of HA.
For the HPLC measurements, 15 mg of MeHA was dissolved in 10 ml of 0.02 M NaOH solution, and incubated at 37°C for 30 minutes to ensure complete hydrolysis of the ester bonds. After that, 2 ml of 2 M acetic acid (Merck) was added to acidify the solution. Samples were filtered over 0.2 μm filters and injected onto a Sunfire RP-18 column (Lichrospher, Darmstadt, Germany). Samples were analyzed using a HPLC Waters 2695 system equipped with an UV detector model 2487 (λ = 210 nm, Waters Inc., Dublin, Ireland). The mobile phase consisted of a mixture of acetonitrile (Actu-All Chemicals, Oss, the Netherlands) and water (ratio: 15/85) adjusted to pH 2 with perchloric acid (HClO₄, 70%, Sigma-Aldrich) and a flow rate of 1 ml/min was used. A calibration curve was obtained by injection of methacrylic acid solutions in eluent with a concentration range of 0 to 160 μg/ml. Empower Pro software (Waters) was used to calculate the concentration of methacrylic acid.

An austenitic
316L stainless SS foil (0.5 mm) was cut into 1 × 1 cm-sized samples.
Prior to anodization, the samples were ultrasonically cleaned in acetone,
ethanol, and distilled water each for 10 min. For anodization, the
samples were connected to a DC power supply (Genesys 300V/5, TDK Lambda),
which had a two-electrode configuration. A platinum mesh was used
as the cathode and a 316L SS sample was used as the anode. 316L SS
samples were anodized in ethylene glycol monobutyl ether (EG, Sigma-Aldrich)
solution containing 7.5% (v/v) perchloric acid (HClO₄,
Sigma-Aldrich) to obtain nanofeatured surfaces. Anodization experiments
were carried out at temperatures lower than 6 °C. To control
the feature size of the nanofeatures, the applied potentials were
altered between 25 and 80 V, and the anodization durations were set
between 1 and 20 min. After the anodization process, all the samples
were rinsed with distilled water and dried at room temperature.