Fig. 5

a–f CVs (at a scan rate of 50 mV/s) in PBS containing 0.01 M 2-ATP at a bare GCE (black lines) or GCEs modified (red lines) with 5 mol% a anatase TiO₂, b Cr-TiO₂, c Mn-TiO₂, d Fe-TiO₂, e Co-TiO₂, and f Ni-TiO₂. g A sluggish oxidation current observed at a bare GCE because of the intrinsically slow oxidation of 2-ATP. h Catalytic currents resulting from the electrochemical oxidation of 2-ATP for the various types of anatase TiO₂ and the five TM-TiO₂