Adsorption behavior of terephthalic acid on Au(100), Au(111) and Au(110) electrodes in neutral solution

Adsorption of terephthalic acid on Au(100), Au(111) and Au(110) electrodes in neutral solution has been investigated using in situ Fourier transform infrared (FT-IR) spectroscopy, differential capacity measurements and scanning tunneling microscopy (STM). At negative potentials, the terephthalate anions in solution adsorb in a flat orientation onto the electrode via the pi electrons of the aromatic ring. At positive potentials, the terephthalate anions adsorb in a vertical orientation via the oxygen atoms of one of the carboxyl groups as a form of dianion. At more positive potentials, the anions adsorb in a vertical orientation as a form of hydrogen terephthalate. For the three electrodes examined, the overtone and/or combination bands, due to vertically oriented hydrogen terephthalate, were observed at 2642 and 2517 cm(-1), respectively. For the Au(111) electrode, STM observations indicated a flat orientation in the form of terephthalic acid. (c) 2008 Elsevier Ltd. All rights reserved.