In-situ electrochemical atomic force microscopy with atomic resolution of Ni(110) in neutral and alkaline aqueous solutions

Bare and anodically oxidized Ni(110) surfaces in 0.05 kmol m(-3) Na2SO4 (pH = 6.5) and 0.01 kmol m(-3) NaOH (pH = 12) aqueous solution have been investigated by in-situ electrochemical atomic force microscopy (EC-AFM) with atomic resolution. We have succeeded in in-situ observation of unreconstructed Ni(110)-(1 x 1) structures in both 0.05 kmol m(-3) Na2SO4 and 0.01 kmol m(-3) NaOH solution. Under passive region, we have observed well-ordered structures differing from those of the bare surfaces and we found that surface structure of anodically oxidized Ni(110) in 0.05 kmol m(-3) Na2SO4 solution agrees with NiO(110), whereas that in 0.01 kmol m(-3) NaOH solution agrees with beta-Ni(OH)(2)(0001). These EC-AFM observations reveal the following orientation relationship of the surface structures on the anodic oxide layers and the substrates: NiO(110)[001]//Ni(110) [001] and NiO(110)[1 (1) over bar0]//Ni(110)[1 (1) over bar0] in neutral solution, and beta-Ni(OH)(2)(0001)[11 (2) over bar0]//Ni(110)[001] and beta-Ni(OH)(2) (0001)[1 (1) over bar 00]//Ni(110)[1 (1) over bar0] in alkaline solution.