We explored the electrochemical behavior of antimony-doped tin oxide (ATO) and perylene diimide (PDI)-sensitized ATO (ATO-PDI) for the (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) mediated conversion of 5-hydroxymethyl furfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a value-added substrate for alternative polymer synthesis. We first showed that ATO displayed good electrocatalytic properties towards TEMPO, affording a quasi-reversible response with a heterogeneous rate constant on the order of 2×10