Extended Data Fig. 5: The importance of Cu(110) for the anti-corrosion properties.

a, STM topographies of the single-crystal Cu(110)-c(6 × 2) sample after exposure to air and then annealing at 120 °C. The zoom-in STM image shows distortion and darker depressions in the Cu(110)-c(6 × 2) superstructure, suggesting the occurrence of a hydration process during air exposure. b, STM image of the single-crystal Cu(110)-c(6 × 2) sample after air exposure followed by annealing at 300 °C. The regeneration of the dehydrated c(6 × 2) structure without dark depressions was confirmed. c, Structure models showing the adsorption of O₂ and Cl⁻ on clean Cu(110) (I, II) and FA-modified Cu(110) (III, IV). O₂ is easily dissociated on clean Cu(110) to form adsorbed O species. The Bader charge of Cu atoms on the modified Cu(110) and reference systems was as follows: (1) modified Cu(110): surface Cu +0.97 to +1.0, subsurface Cu +0.34 to +0.53, bulk Cu 0 to +0.14; (2) reference systems: bulk CuO +0.99, bulk Cu₂O +0.57, Cu(110) +0.01 to −0.02. d, XRD patterns of Cu(100), Cu(111) and Cu(110) single crystals. e, XRD patterns of scratched Cu(111) single crystal treated with formate at 160 °C for 0–60 h. If the surface was not scratched, no change on the XRD pattern was detected even for treatment time of up to 60 h. f, Micrographs and Raman spectra of Cu(110), Cu(100) and Cu(111) single-crystal samples treated by an aqueous solution of formate at 100 °C for 1 h, 10 h and 10 h, respectively. The two groups of Raman bands at (146, 217, 416, 535) cm⁻¹ and 635 cm⁻¹ are attributed to the Cu₂O and CuO species, respectively⁶⁸.