Pgstat302n

Electrocatalytic HER measurement of all samples was carried out on an electrochemical workstation (Metrohm, PGSTAT302N, Herisau, Switzerland) in a three-electrode cell at room temperature. The three-electrode system was composed of a self-supporting working electrode, a graphite rod counter electrode, and a Hg/HgO (1 M KOH) reference electrode. The measured potential was converted to a reversible hydrogen electrode (RHE) using the following equation:
Linear sweep voltammetry (LSV) was carried out at the scan rate of 0.002 V/s to evaluate the overpotential and Tafel slope during the HER process. Cyclic voltammetry (CV) was performed at various scan rates ranging from 0.04 to 0.12 V/s to estimate the ECSA of the electrocatalyst. In addition, electrochemical impedance spectroscopy (EIS) was recorded at an overpotential of 74.6 mV with a 10 mV amplitude in the frequency range from 100 kHz to 0.1 Hz. Prior to the electrochemical test, Ar gas (≥99.999%) was bubbled into the electrolyte for 20 min to preclude the inference of the oxygen reduction reaction. All LSV potentials were demonstrated through a 95% iR-compensation based on the EIS results. All current densities were demonstrated after normalization using the geometric area of the electrocatalyst.

Transmission electron microscopy (TEM) images were obtained on a JEM-2100 microscope (JEOL, Japan) at an acceleration voltage of 200 kV. VMSF was mechanically peeled off from the ITO electrode surface, dispersed into ethanol, and finally dropped onto copper grids, to obtain TEM specimen. Scanning electron microscopy (SEM) images were collected from the SU8100 microscope (Hitachi, Japan) at an acceleration voltage of 10 kV. Cyclic voltammetry (CV) was taken on an Autolab PGSTAT302N electrochemical workstation (Metrohm, Switzerland). A conventional three electrodes system was employed with bare ITO or modified ITO electrode as the working electrode, an Ag/AgCl electrode (saturated with KCl) as the reference electrode, and a platinum electrode as the counter electrode.

Corrosion performance was tested in dilute Harrison’s solution [58 ] (3.5 g/L (NH₄)₂SO₄ + 0.5 g/L NaCl) using electrochemical impedance spectroscopy (EIS). Measurements were made in a three-electrode corrosion cell placed in a Faraday cage. An area of 1 cm² of the sample was exposed to the corrosive solution. As the reference electrode, a silver/silver chloride (Ag/AgCl, sat. KCl, E = 0.197 V vs. saturated hydrogen electrode) was used. A carbon rod served as a counter electrode. Electrochemical experiments were carried out with an Autolab PGSTAT302N (Metrohm Autolab, Utrecht, The Netherlands) potentiostat/galvanostat and controlled by Nova 1.11 software. EIS measurements were acquired in the frequency range from 100 kHz to 10 mHz with a 10 mV amplitude signal. Prior to measurement, the open circuit potential (OCP) was measured for 10 min. The EIS measurements were performed at the OCP, the first after 1-h immersion and then after regular intervals up to 4 months.

The morphology of bp-SNF was observed using transmission electron microscopy (TEM, JEM-2100, JEOL, Tokyo, Japan) and scanning electron microscopy (SEM, SU8010, Hitachi, Tokyo, Japan). For the TEM investigation, bp-SNF was gently scraped from the surface of the ITO electrode and dispersed in ethanol. After ultrasonic treatment, the resulting solution was dropped onto the supporting copper mesh. All electrochemical tests were conducted at the Autolab electrochemical workstation (PGSTAT302N, Metrohm, Herisau, Switzerland). The three-electrode system was applied. Briefly, bare or modified ITO electrode acted as the working electrode, a platinum wire was the counter electrode, and an Ag/AgCl electrode (saturated with KCl) was applied as the reference electrode. The supporting electrolyte solution was KHP (0.05 M). The concentration of the two standard electrochemical probes including K₃Fe(CN)₆ and Ru(NH₃)₆Cl₃ was 0.5 mM. The scanning rate for the cyclic voltammetry (CV) measurement was 50 mV/s. The parameters for the differential pulse voltammetry (DPV) measurement including step potential, pulse amplitude, pulse time, and interval time were 0.005 V, 0.05 V, 0.05 s, and 0.2 s, respectively.

Optical absorption spectra of the BBL-P films were taken on a PerkinElmer Lambda 900 spectrometer. For spectroelectrochemistry, BBL-P thin film was coated on FTO substrates which were inserted into a cuvette filled with 0.1 M KCl_(aq) as the electrolyte. The polymer film area was 2.75 ± 0.18 cm², and the polymer film thickness was 44.4 ± 8.8 nm. Three-electrode configuration containing Ag/AgCl pellet as the reference electrode, Pt mesh as the counter electrode, and FTO/BBL-P as the working electrode was used. A Metrohm Autolab PGSTAT302N potentiostat was used to control the potential via the Metrohm NOVA software (Version 2.1.6). The BBL-P working electrodes were biased at different potentials for 60 s for doping to be equilibrated before collecting the optical absorption spectra. The films were thoroughly de-doped by applying +0.5 V (vs. Ag/Ag⁺) between each doping cycle. Both the doping and the de-doping currents were simultaneously collected during the optical measurements for coulometry analysis. The electrolyte was degassed by purging with N₂ stream for at least 20 min prior to measurements.