In situ AFM studies of the stability of MgO(1 0 0) in aqueous electrolytes

• Stability and dissolution of MgO(1 0 0) surfaces in alkaline solutions of NaCl and NaClO4.
• Stability determined by the hydrogen network between the water and the oxide surface.
• Formation of a hydroxide gel-like layer in absence of chloride.
• Report of square pits oriented in the 〈1 1 0〉 directions during immersion in NaCl.
• Substitution of hydroxides by chlorides at the electrolyte/MgO interface.

The stability and dissolution of MgO(1 0 0) single crystal surfaces in alkaline solutions of NaClO4 and NaCl were investigated by means of in situ atomic force microscopy (AFM) and ex situ angle resolved X-ray photoelectron spectroscopy (AR-XPS). MgO surfaces showed higher resistance to dissolution in NaClO4 electrolyte due to the formation of a gel-like hydroxide layer. The emergence of rectangular/square formed pits oriented in the 〈1 1 0〉 directions during immersion in NaCl electrolytes at alkaline pH was observed. The results are discussed on the basis of a substitution of hydroxides by chlorides at the electrolyte/MgO interface.

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