Electrodeposition of gold on fluorine-doped tin oxide: Characterization and application for catalytic oxidation of nitrite

Sub-micrometer size gold particles were electrodeposited on a transparent fluorine-doped tin oxide (FTO) from acetonitrile solution containing AuCl ₄ - and tetramethylammonium tetraflouroborate (TMATFB) for detecting NO₂ -. A series of two-electron (2e-) and one-electron (1e-) reductions of the AuCl₄ -AuCl₂ -Au redox systems were observed at FTO and a highly stable and homogeneous distribution of Au on FTO (Au/FTO) was obtained by stepping the potential from 0 to -0.55 V (vs. Ag/Ag+). The Au/FTO electrode exhibited sufficiently high catalytic activity toward the oxidation of NO₂ - with a detection limit (S/N = 3) and sensitivity of 2.95 μM and 223.4 μA•cm-2•mM-1, respectively, under optimal conditions. It exhibited an interference-free signal for NO₂ - detection with excellent recoveries from real samples.