Alpha ra 8

A conventional three-electrode electrochemical cell was used for electrochemical measurements. The fabricated NiMo/Ti and Au(NiMo)/Ti catalysts were employed as working electrodes, a Pt sheet was used as a counter electrode, and a calomel electrode was used as a reference. All potentials in this work were converted to the reversible hydrogen electrode (RHE) scale using the following Equation (5):
Current densities were calculated using the electrodes’ geometric area of 2 cm². Linear sweep voltammograms were recorded in a 1 M NaOH solution and always deaerated by argon (Ar) for 20 min prior to measurements. HER polarization curves were recorded from the open circuit potential (OCP) to −0.42 V (vs. RHE) at a polarization rate of 10 mV·s⁻¹. Polarization curves were recorded at several temperatures from 25 to 75 °C, and temperatures were set with a water jacket connected to a LAUDA Alpha RA 8 thermostat. Stability was studied by recording chronoamperometry (CA) curves for HER at a potential of −0.22 V (vs. RHE) for half an hour. All electrochemical measurements were performed with a Metrohm Autolab potentiostat (PGSTAT302, Utrecht, The Netherlands) using the Electrochemical Software (Nova 2.1.4).

Carbon steel L360NB was chosen since this is the commercialized and realistic material for CO₂ transport pipeline. The chemical composition of this steel is shown in Table 1. From the as-received pipeline sections, testing coupons were machined to the size of 20 mm × 15 mm × 5 mm. Typical sample preparation included mechanical polishing using 60, 120, and finally, 320 grit silicon carbide abrasive papers, cleaning with ethanol and degreasing with acetone and drying using nitrogen gas prior to every test. The mass and the dimensions of the specimens were measured for weight loss calculation. Experimental condition is summarized in Table 2.
All tests in this study were conducted in a system consisting of three double-walled glass cells connected to a cooling system (Alpha RA8, Lauda, Lauda-Königshofen, Germany) to maintain the temperature at 278 K (5 °C). Each cell has 4 ports to purge the CO₂ gas (purity > 99.995%, Linde AG, Germany) (50–60 mL/min) and to insert working, counter, and Ag/AgCl reference electrodes. In the case of exposure test, the coupon was hanged on the Teflon wire, while in the electrochemical test, the coupons were weld to a stick made of high-alloyed material. Before each test, 500 mL condensate was used and purged strongly with Ar (purity > 99.998%, Linde) for 30 min, then 1 h with CO₂ to reach the saturation state and stable pH (≈1.9).