ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Stoichiometry influence of oxide support on the catalytic efficiency of nano-palladium towards CH₃OH electrooxidation

Zahra Yavari, Shervin Shaybani, Jilla Saffari, Kagan Kerman, and Meissam Noroozifar

Department of Chemistry, University of Sistan and Baluchestan, Zahedan, Iran

E-mail: z_yavari@chem.usb.ac.ir

Received: 15 July 2020  Accepted: 19 December 2020

Abstract:

Abstract

Improving the yield of catalysts containing palladium for the polymeric fuel cells is the main challenge in the commercializing of this technology. The utilization of transition metal oxides as the promoters can be an efficient solution for more poisoning removal of the catalyst. The stoichiometry effect of the oxide support on the activity of Pd for electrooxidation of the CH₃OH is presented in this study. The lanthanum nickelate substitutes with different ratios of Fe:Ni (1:4, 1:1, and 4:1) are synthesized and characterized using SEM, EDX, XRD, FT-IR, and VSM analyses. The proposed oxide samples are in the Ruddlesden–Popper salts group with general chemical formula (LaNi_xFe_1−xO₃)_nLaO and the crystal structure of the lanthanum nickelate is changed from orthorhombic to rhombohedral with the increasing ratio of nickel to iron. Also, the nano-sized Pd catalyst is anchored on as-prepared oxides via wetness incorporation. The behavior and efficiency of as-prepared electrocatalysts are compared with each other using the electrochemical techniques. Based on the results, the current density presented an ascending trend from 92.07 to 130.83 mA/cm² for 0.8 M CH₃OH by increasing the Fe ratio. It means that the nanocomposites containing more iron improved the catalytic ability of palladium and the reaction kinetics of the CH₃OH oxidation. The functions of current and transferred charge vs. time are, respectively, obtained to simulate and integrate chronoamperometric data for oxidation of CH₃OH. It seems the lattice oxygens, and the activation of an oxidation–reduction cycle between the high and low chemical valences of iron, leading to progress the catalytic performance of palladium.

Graphic abstract

Keywords: Chronoamperometry; Lattice oxygen; Ruddlesden–popper salt; Lanthanum nickelate; Fuel cell; Transition metal oxides

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01485-8

Chemical Papers 75 (6) 2317–2329 (2021)