Synthesis and characterization of LaNiO 3-based platinum catalyst for methanol oxidation

Abstract

Conductive perovskite type lanthanum nickelate (LaNiO 3) powders are prepared through a nitrilotriacetic acid (NTA) precursor complex route. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) results indicate complete decomposition of the precursor complex to LaNiO 3 at 900 °C in 4 h. Powder X-ray diffraction (XRD) patterns confirm the formation of the perovskite. Scanning electron microscopic (SEM) analysis and particle size determination reveal the formation of micron-sized particles, probably by the agglomeration of nanoparticles of LaNiO 3. Cyclic voltammetry (CV) is used to assess the electrochemical activity of LaNiO 3 in comparison with Pt/C, as well as the addition of small amounts of Pt/C to LaNiO 3 or a Vulcan XC-72R carbon support of three different compositions, towards methanol electro-oxidation. LaNiO 3 does not show much activity for methanol oxidation. However, a synergistic effect is observed when LaNiO 3 is mixed with small amounts of Pt/C. The increased oxidation current due to the addition of LaNiO 3 to small amounts of Pt/C in the three mixtures containing LaNiO 3 is attributed to either the additional catalyst site of the perovskite in addition to the Pt site, or the removal of CO poisoning on the Pt surface by the surface oxygen of the adjacent perovskite.