Pt-Doped and Pt-Supported La1-xSrxCoO3: Comparative Activity of Pt4+ and Pt0 Toward the CO Poisoning Effect in Formic Acid and Methanol Electro-oxidation

Pt-supported La<inf>1-x</inf>Sr<inf>x</inf>CoO<inf>3</inf> and Pt-doped La<inf>1-x</inf>Sr<inf>x</inf>CoO<inf>3</inf> are synthesized using chemical reduction and solution combustion method, respectively. Chemical reduction is carried out using formaldehyde as a reducing agent giving Pt-supported La<inf>1-x</inf>Sr<inf>x</inf>CoO<inf>3</inf>. Solution combustion method is used to prepare Pt-doped La<inf>1-x</inf>Sr<inf>x</inf>CoO<inf>3</inf>. Detailed characterization using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area measurement, and transmission electron microscopy (TEM) is carried out to distinguish the Pt-supported and Pt-doped compounds in terms of their morphology and Pt oxidations states. TEM results indeed show the differences in their morphology. Further, electrochemical measurements are performed in neutral medium to differentiate their electrochemical activity. Cyclic voltammetry (CV) shows noticeable differences between Pt-supported La<inf>1-x</inf>Sr<inf>x</inf>CoO<inf>3</inf> and Pt-doped La<inf>1-x</inf>Sr<inf>x</inf>CoO<inf>3</inf>. Importantly, our results show that Pt⁴⁺ in doped compound has poor to zero electrocatalytic activity toward formic acid and methanol electro-oxidation in comparison to Pt⁰ in supported compound. This study shows that metallic Pt in zero oxidation state is a superior catalyst to Pt in +4 oxidation state.