Metal-support interactions in electrocatalysis: influence of supports containing carbides on oxygen reduction in Pd nanoparticles

Author(s)

Gabriel Martins de Alvarenga

• Document type: Doctoral Thesis
• Press: Araraquara. 2021-05-05.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara
• Defense date: 2021-04-28
• Advisor: Hebe de las Mercedes Villullas

Abstract

Metal-support interactions can modify the electronic properties of the metal, which can considerably modify the speed of steps of the reaction mechanism where adsorbed species participate. This thesis presents a comparative and systematic study of the effects of alternative supports on the electrocatalysis of the oxygen reduction reaction on Pd nanoparticles in acidic and alkaline media, that was studied on Pd nanoparticles supported on hybrids carbon-carbide (C-SiC, C-TiC and C-WC) and on pure carbides (SiC, TiC and WC) aiming to elucidate the influence of the supports on the catalytic activity of Pd. These studies were performed comparing the catalytic responses for the oxygen reduction reaction of catalysts prepared with identical Pd nanoparticles and analyzing the effect of different carbides with the same particle size (TiC – 50nm vs. SiC – 50nm; TiC – 200 nm vs. WC – 200nm), as well as by evaluating the effects of particle size of the carbide (TiC – 50nm vs. TiC – 200nm). Besides characterizing the catalysts by X-ray diffraction (XRD) and transmission electron microscopy (TEM), the effects of metal-support interactions on the electronic occupancy of the Pd 4d band were investigated by in situ X-ray absorption spectroscopy (XAS). The catalytic activity for the oxygen reduction reaction and the stability of the materials were evaluated by electrochemical techniques (rotating ring disc electrode and cyclic voltammetry). This work demonstrated the effects of supports containing carbides on the Pd electronic properties and their relation with the catalytic activity for the oxygen reduction reaction and aimed to contribute to the understanding of the factors that influence the catalytic activity of Pd catalysts and to the development of Pt-free catalysts for fuel cell cathodes. (AU)

• FAPESP's process: 18/20780-4 - Metal-support interactions in electrocatalysis: influence of supports containing carbides on the oxygen reduction reaction on PD nanoparticles
• Grantee: Gabriel Martins de Alvarenga
• Support Opportunities: Scholarships in Brazil - Doctorate