Interface 1000 electrochemical workstation

An Interface 1000 electrochemical workstation (Gamry Instruments, Warminster, PA, USA) was used for electrochemical measurements. A three-electrode electrochemical cell was used with a platinum plate as a counter electrode and a saturated calomel electrode (SCE) as a reference electrode. BG90SS steel and the Ni-based alloy coating specimens were respectively employed as the working electrode (WE). After the WE was immersed in the solution for 30 min to obtain a stable open circuit potential (OCP), the potentiodynamic polarization curve was carried out in a range of −500 mV–1000 mV with respect to the corrosion potential, and with a scan rate of 0.5 mV/s. All the potentials in this study referred to this reference electrode.
The test solution to simulate the formation water from a gas condensate field in China was made up of analytical grade reagents and deionized water. The chemical composition of the test solution is listed in Table 2. Prior to the tests, the solution was purged with N₂ (99.99%) for at least 4 h, and then the test solution was saturated with H₂S/CO₂ mixed gases at a speed of 200 mL/min for 1 h. Afterwards, the WE was immersed in the solution, and the H₂S/CO₂ mixed gases were then bubbled through the solution at a low flow rate of 20 mL/min. The tests were performed under static conditions at 25 °C and atmospheric pressure (H₂S/CO₂ pressure was 0.1 MPa).

The electrochemical
characterizations
were conducted using the Biologic MPG-2 Battery Testing System at
room temperature. Galvanostatic cycling tests were measured in two-electrode
cells, first discharged-charged at a constant current density of 0.1
mA cm^–2 within a voltage window of 2.0 to 0.0 V
(vs Li⁺/Li) for five initial formation cycles and then
discharged at a certain content current density (i.e., 0.2, 0.5, 1.0,
or 2.0 mA cm^–2) under constant capacity conditions
(i.e., 0.5, 1.0, 2.0, or 5.0 mAh cm^–2) in subsequent
cycles. The electrochemical impedance spectroscopy (EIS) was recorded
by using three-electrode cells in a frequency range from 100 mHz to
100 kHz. The ex situ EIS curves of the t-CN@Cu electrode were collected
at various selected SOCs during the first formation cycle. The galvanostatic
intermittent titration technique (GITT) was measured with a polarization
process consisting of a current pulse of 0.1 mA cm^–2 for 10 min followed by an open circuit stand process for 60 min
to relax to quasiequilibrium potential. The detailed calculation of
Li⁺ chemical diffusion coefficients is shown in Supporting Information. The Tafel plots were
obtained on a Gamry Interface 1000 electrochemical workstation at
a scan rate of 0.1 mV s^–1 between −0.3 and
0.3 V (vs Li⁺/Li).