Extended Data Fig. 6: Enhanced anti-corrosion performance in harsh conditions by introducing alkanethiol.

a, Structure model of Cu-FA with alkanethiol bound to the step sites, and experimental evidence of the successful introduction of 1-DT ligands. Whereas the change of contact angle of the water droplets suggests the change of surface hydrophobicity, TPD-MS confirms the presence of formate and DT on Cu-FA/DT. The Cu-FA foils were prepared by Method III. b, Electrochemical measurements (CV, Tafel, Nyquist impedance and Bode plots) confirming the enhanced anti-corrosion properties of Cu-FA after the DT treatment. All measurements were carried out in 0.1 M NaOH solution. The Nyquist impedance and Bode plots were measured at 0.1 V versus Ag/AgCl. The polarization parameters of Cu-FA/DT foils in 0.1 M NaOH and 1 M NaOH are: E_corr = −258 mV, J_corr = 0.067 μA cm⁻², corrosion rate 0.755 μm yr⁻¹, anti-corrosion enhancement 103.6 (0.1 M NaOH); E_corr = −331 mV, J_corr = 0.38 μA cm⁻², corrosion rate 4.40 μm yr⁻¹, anti-corrosion factor 158.1 (1 M NaOH). The anti-corrosion factor is defined as the ratio of the corrosion rate of the bare Cu foil to that of the modified Cu in the same NaOH solutions. c, Comparison of optical images and Raman spectra for the evaluation of the enhanced anti-corrosion of Cu-FA (prepared by Method III) against salt spray after introducing DT. Before the measurements, Cu, Cu-FA and Cu-FA/DT foil samples were subjected to a 5% NaCl salt spray test at 47 °C for 24 h. The Raman bands around (149, 217) cm⁻¹ and 640 cm⁻¹ are attributed to Cu₂O and CuO species, respectively⁶⁸. d, Comparison of optical imaging data that reveals the enhanced anti-corrosion of Cu-FA/DT against Na₂S. Before recording the images, both Cu-FA and Cu-FA/DT foils were exposed to Na₂S solutions with concentrations ranging from 0.1 mM to 1 M for 1 h. Compared to Cu-FA, Cu-FA/DT could survive and keep its copper colour in a much higher concentration of Na₂S. e, SEM images and Raman spectra of Cu-FA and Cu-FA/DT after treatment in 10 mM Na₂S for 1 h and 5 h, respectively. The Raman bands around 296 cm⁻¹ and 624 cm⁻¹ indicate the formation of oxidized and sulfurized Cu species. f, SEM images of Cu, Cu-FA and Cu-FA/DT foils after seawater inundation at room temperature for 30 days. g, Photographs showing enhanced anti-corrosion of Cu-FA/DT in H₂O₂. The photographs of the Cu-FA/DT, Cu-FA and Cu foils were taken after they were immersed in 30% H₂O₂ for different intervals.