Domain-selective reactivity of hydroquinone-derived adlayers at basal Pt(hkl) single-crystal electrodes

The electrochemical reactivity of hydroquinone-derived adlayers (Q((ads))) is compared at basal Pt(hkl) single-crystal surfaces, revealing that the electrochemically controlled desorption of Q((ads)) is a highly selective surface reaction. At well-ordered Pt(111) single-crystal surfaces, classical electrochemical methods are combined with in situ SNIFTIRS measurements to demonstrate that the reductive desorption of Q((ads)) and their full oxidative readsorption can be achieved, even in the presence of hydroquinone solution (H(2)Q(aq)), by controlling the potential of Pt(111) electrodes. At well-ordered Pt(111) domains, the presence of vertically adsorbed molecules within the Q((ads)) adlayer is deduced from the spectroelectrochemical SNIFTIRS measurements. The desorption mechanism, detected voltammetrically at Pt(111) electrodes, is precluded at well-ordered Pt(110) and Pt(100) single-crystal electrodes immersed in hydroquinone-containing solutions, requiring the presence of well-ordered Pt(111) surface domains in order to be detected. In clean supporting electrolyte, the partial desorption of Q((ads)) layers may take place, but predominantly from minority surface imperfections at Pt(110) and Pt(100) via a different mechanism than at Pt(111) surface domains.