Electrochemical carboxylation of titanium to generate versatile new interfaces
Abstract
Titanium covered with a thin layer of titanium dioxide was reduced in aprotic polar solvents (dimethylformamide or acetonitrile) saturated with carbon dioxide in the presence of tetraalkylammonium salts (TAAX). When using tetramethylammonium salts CO2 is irreversibly reduced at potentials andlt; −1.6 V vs. Ag/AgCl/KClsat, generating an inactive surface down to −3.2 V. Anodic oxidation of the modified surface in the same solvent led to regeneration of a titanium interface free of oxide. Employing other TAAX salts permits reversible reduction of CO2 (Ep/2 = −2.21 V in the presence of TBuABF4). Under conditions of total passivation of the Ti surface followed by sonication, stable electrode surfaces inactive in organic polar solvents between −3 V and +2 V were obtained. Within the cathodic range, several organic π-acceptors were reversibly reduced down to −3 V, which shows the potential of such “Ti-CO2” surfaces as new working electrodes. © 2018