In situ x-ray scattering studies of the Pt(110) electrode show that a
stable (1 x 2) reconstruction is present over a wide electrode potenti
al range and that the topmost rows of Pt atoms are expanded into the e
lectrolyte. Additional expansion occurs upon the potential-induced ads
orption of hydroxyl or hydrogen atoms. The presence, and stability of
the (1 x 2) reconstruction have an important influence on some of the
surface reactions that can occur in electrolyte.