Preparation and Characterization of Ti/SnO2-Sb Electrodes without or with a Platinum Interlayer Using the Polymeric Precursor Method and Thermal Decomposition

Abstract

SnO2-Sb electrodes on a Ti substrate, prepared without (Ti/SnO2-Sb) or with a Pt interlayer (Ti/Pt/SnO2-Sb), were prepared using the polymeric precursor method followed by thermal decomposition. The platinum film on titanium (Ti/Pt) was prepared by thermal decomposition of an alcoholic solution of Pt. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and elemental mapping were used to characterize the surfaces of Ti/Pt, Ti/SnO2-Sb, and Ti/Pt/SnO2-Sb. The electrochemical characterization of the electrodes was performed using cyclic voltammetry in a 0.5 M H2SO4 solution. The electroactive area of the electrodes was determined using measurements of the electrosorption hydrogen charge for Ti/Pt and the capacitance of the electric double layer for Ti/SnO2-Sb and Ti/Pt/SnO2-Sb. Tafel slopes for the oxygen evolution reaction (OER) were estimated from polarization curves. The SEM and EDS results obtained from the electrodes prepared with or without a platinum interlayer displayed distinct behaviors. In the absence of Pt, the SnO2-Sb coating on titanium formed a compact layer with a good distribution of Sn, Sb, O, and a low Ti content. In the presence of the Pt coating, SnO2-Sb was heterogeneously distributed. The heterogeneous character of the Ti/Pt/SnO2-Sb film resulted from surface segregation during the calcination process. The voltammetric behaviors of the SnO2-Sb electrodes prepared with or without a Pt interlayer displayed similar trends, although the presence of Pt produced a greater electroactive area and shifted the oxygen evolution potential toward less positive values; therefore, the electrocatalytic activity toward the OER was higher compared to the Ti/SnO2-Sb electrode. The Tafel slope estimated for Ti/Pt/SnO2-Sb is consistent with a mechanism in which OH- generation is the rate controlling step.