Azo dyes as electron transfer mediators in the electrochemical reduction of Cr(VI) using boron-doped diamond electrodes

► Boron doped diamond electrodes were used to electrochemically reduce Cr(VI). ► Methyl orange, methylene blue, and thionine azo dyes enhance the reduction. ► 90% of Cr(VI) is reduced and 98% of the methyl orange is oxidized.