Electrochemical oxidation of toluene with controlled selectivity: The effect of carbon anode

Benzaldehyde is much easier to be oxidized than toluene, which makes the selective oxidation of toluene to benzaldehyde highly challenging. Here, we investigated the electrochemical oxidation of toluene to benzaldehyde via direct electron transfer at a carbon electrode. Selectivity to benzaldehyde depended on the current and electrode type, being highest (92%) for a graphite rod. The higher selectivity to benzaldehyde at graphite rod attribute to its high electrochemically active surface area and the large number of defect sites, which favorably absorb benzaldehyde, thereby preventing further oxidation to benzoic acid. Tafel analysis revealed the rate-determining step in the electrochemical toluene oxidation reaction, which has been underexplored previously. The developed method was successfully applied to other para-substituted toluene and was therefore well suited for the sustainable production of benzaldehyde derivatives.