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

Abstract

Bare and anodically oxidized Ni(110) surfaces in 0.05 kmol m -3Na 2SO 4(pH=6.5) and 0.01 kmol m -3NaOH(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 × 1) structures in both 0.05 kmol m -3 Na 2SO 4 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 -3Na 2SO 4 solution agrees with NiO (110), whereas that in 0.01 kmol m -3 NaOH solution agrees withβ-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) [11̄0]//Ni(110)[11̄0] in neutral solution, and β-Ni(OH) 2(0001)[112̄0]//Ni (110) [001] and β-Ni(OH) 2 (0001)[11̄00]//Ni (110) [11̄0] in alkaline solution.