Adsorption of hydroquinone (QH(2)) onto a polycrystalline gold electrode surface in an unbuffered aqueous solution was confirmed by cyclic voltammetry (CV) and time-of-flight secondary ion mass spectrometry. The adsorption appeared to inhibit direct electron transfer between QH(2) in the solution and the gold electrode. CV indicated that the surface coverage was ca. 9 x 10(-1)1 mol cm(-2). It was also demonstrated that when QH(2) was electrochemically oxidized, the adsorbed QH(2) likely desorbed from the gold surface. (C) 2017 The Electrochemical Society.