The electroreduction of benzoic acid: voltammetric observation of adsorbed hydrogen at a platinum microelectrode in room temperature ionic liquids

Abstract

The electrochemical reduction of benzoic acid in the presence and absence of hydrogen (H₂) has been investigated using a 10 μm diameter platinum microelectrode in four different room temperature ionic liquids (RTILs), namely [C₄mim][NTf₂], [C₄mpyrr][NTf₂], [C₄mim][OTf] and [C₄mim][BF₄], versus Ag/Ag⁺. In all cases, reductive voltammetry is observed, and is suggested to occur via a CE mechanism in which dissociation of benzoic acid is followed by electron transfer to H⁺ ultimately forming adsorbed hydrogen. Furthermore, the adsorbed H atoms, formed from the reduction of benzoic acid, could be used to achieve the rapid hydrogenolysis of the organic compound (bis(benzyloxycarbonyl)-L-lysine) on the timescale of the voltammetric technique under moderate conditions (25 °C).