Development of a Au/TiO2/Ti Electrocatalyst for the Oxygen Reduction Reaction in a Bicarbonate Medium

The oxygen reduction reaction (ORR) is a pivotal electrochemical process in energy technologies and in the generation of hydrogen peroxide (H2O2), which serves as both an effective agent for dye degradation and a fuel in H2O2-based fuel cells. In this regard, a titanium (Ti) sheet was anodized to generate a TiO2 layer, and then the oxide layer was modified with gold (presented as Au/TiO2/Ti) via electrodeposition. The developed electrocatalyst was confirmed by X-ray photoelectron spectroscopy (XPS), which showed characteristic binding energies for Ti4+ in TiO2 and metallic Au. In addition, the Nyquist plot verified the electrode modification process, since the diameter of the semicircular arc, corresponding to charge transfer resistance, significantly decreased due to Au deposition. Voltametric studies revealed that the TiO2 layer with a Ti surface exhibited a good synergistic effect on Au and the ORR in a bicarbonate medium (0.1 M KHCO3) by lowering the overpotential, enhancing current density, and boosting durability. The scan rate-dependent study of the ORR produced by the developed electrocatalyst showed a Tafel slope of 180 ± 2 mV dec−1 over a scan rate range of 0.05–0.4 V s−1, thereby indicating a 2e− transfer process in which the initial electron transfer process was the rate-limiting step. The study also revealed that the Au/TiO2/Ti electrode caused oxygen electro-reduction with a heterogenous rate constant (k0) of 4.40×10−3 cm s−1 at a formal potential (E0′) of 0.54 V vs. RHE.