title: La2O3Promoted Pd/rGO Electro-catalysts for Formic Acid Oxidation.
abstract: High activity, a low rate of CO poisoning, and long-term stability of Pd electro-catalysts are necessary for practical use as an anode material in direct formic acid fuel cells. Achieving a high degree of Pd nanoparticle dispersion on a carbon support, without agglomeration, while maintaining a facile electron transfer through the catalyst surface are two challenging tasks to be overcome in fulfilling this aim. Herein, we report the effect of addition of La/La-oxides on the efficiency of Pd nanoparticles supported on reduced graphene oxide (rGO) for formic acid electro-oxidation reaction. A series of electro-catalysts with different Pd-La molar ratios were successfully synthesized and characterized using a range of techniques including PXRD, XPS, TEM, FTIR, and Raman spectroscopy and then tested as anode materials for direct formic acid fuel cells. We explore that the lanthanum species (La/La-oxide) significantly promote the activity and stability of Pd catalyst toward electrocatalytic oxidation of formic acid. The metallic ratio is found to be critical, and the activity order of various catalysts is observed as follows; Pd30La70/rGO > Pd80La20/rGO > Pd70La30rGO. The obtained mass specific activity for Pd30La70/rGO (986.42 A/g) is 2.18 times higher than that for Pd/rGO (451 A/g) and 16 times higher than that for Pd/C (61.5 A/g) at given onset peak potentials. The high activity and stability of the electro-catalysts are attributed to the uniform dispersion of Pd nanoparticles over the rGO support, as evidenced from TEM images. It is believed that the role of La species in promoting the catalyst activity is to disperse the catalyst particles during synthesis and to facilitate the electron transfer via providing a suitable pathway during electrochemical testing.
authors.affiliation: Catalysis and Nanomaterials Lab 27, Department of Chemistry, Quaid-i-Azam University , Islamabad 45320, Pakistan.
authors.forename: Hassan
authors.initials: H
authors.lastname: Ali
authors.affiliation: School of Chemistry, University of New South Wales , Sydney, New South Wales 2052, Australia.
authors.forename: Fehmida K
authors.initials: FK
authors.lastname: Kanodarwala
authors.affiliation: Catalysis and Nanomaterials Lab 27, Department of Chemistry, Quaid-i-Azam University , Islamabad 45320, Pakistan.
authors.forename: Imran
authors.initials: I
authors.lastname: Majeed
authors.affiliation: School of Chemistry, University of New South Wales , Sydney, New South Wales 2052, Australia.
authors.forename: John Arron
authors.initials: JA
authors.lastname: Stride
authors.affiliation: Catalysis and Nanomaterials Lab 27, Department of Chemistry, Quaid-i-Azam University , Islamabad 45320, Pakistan.
authors.forename: Muhammad Arif
authors.initials: MA
authors.lastname: Nadeem
keywords: cyclic voltammetry; fuel cell; graphene; lanthanum oxide; palladium nanoparticles