Electron transfer dynamics and electrocatalytic oxygen evolution activities of the Co(3)O(4) nanoparticles attached to indium tin oxide by self-assembled monolayers

The Co(3)O(4) nanoparticle-modified indium tin oxide-coated glass slide (ITO) electrodes are successfully prepared using dicarboxylic acid as the self-assembled monolayer through a surface esterification reaction. The ITO-SAM-Co(3)O(4) (SAM = dicarboxylic acid) are active to electrochemically catalyze oxygen evolution reaction (OER) in acid. The most active assembly, with Co loading at 3.31 × 10(−8) mol cm(−2), exhibits 374 mV onset overpotential and 497 mV overpotential to reach 1 mA cm(−2) OER current in 0.1 M HClO(4). The electron transfer rate constant (k) is acquired using Laviron’s approach, and the results show that k is not affected by the carbon chain lengths of the SAM (up to 18 -CH(2) groups) and that an increase in the average diameter of Co(3)O(4) nanoparticles enhances the k. In addition, shorter carbon chains and smaller Co(3)O(4) nanoparticles can increase the turn-over frequency (TOF) of Co sites toward OER. The Co(3)O(4) nanoparticles tethered to the ITO surface show both a higher number of electrochemically active Co sites and a higher TOF of OER than the Co(3)O(4) nanoparticles bound to ITO using Nafion.