Studies of the activity of nickel based catalysts, supported on carbon, toward glycerol electrooxidation

Author(s)

Vanessa Luciane Oliveira

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2013-12-06

Examining board members

Germano Tremiliosi Filho; Adalgisa Rodrigues de Andrade; Flávio Colmati Junior; Kouakou Boniface Kokoh; Paulo Olivi

• Advisor: Germano Tremiliosi Filho

Abstract

Carbon supported nickel nanomaterials were synthesized by different routes and evaluated toward the oxidative transformation of glycerol in alkaline medium. The impregnation method, followed by heat-treatment in reducing H2 atmosphere for 2 hours, was chosen by providing a more active material. This method was used to prepare catalysts with metal loadings of 20 wt. %, such as CoNi/C, FeNi/C and FeCoNi/C. Physical characterizations of the materials were performed by using Thermogravimetric Analysis-Differential Thermal Analysis (TGA-DTA) and X-Ray Diffraction (XRD) to determine their metallic load and the crystallite size, respectively. Cyclic voltammetry was mainly used to evaluate the electrochemical activity of the catalysts for glycerol oxidation reaction. The results demonstrated that nickel oxyhydroxide, β-NiOOH, is the active catalytic specie for the glycerol oxidation reaction in alkaline medium. Since the formation of cobalt and iron oxy-hydroxides occurs at lower potentials than those of nickel, amounts of cobalt and iron were added to modify the Ni material. Studies under several well defined experimental conditions were performed by Cyclic Voltammetry. The process of glycerol oxidation was influenced by the scan rate, temperature, glycerol and NaOH concentration. The linear relationship between the peak current density and square root of scan rate corresponds to a diffusion-controlled process for glycerol oxidation on Ni/C. It was found that both the Ipeak and Epeak are strongly depending on the glycerol concentration. In a selected potential chronoamperometry experiments were carried out and the glycerol oxidation products on the Ni-based anodes were analyzed by High-Performance Liquid Chromatography (HPLC). The glycerol conversion depends on the catalyst composition and the distribution. The products were correlated with those identified by infrared reflectance spectroscopy, which supported the simplified mechanism proposed. (AU)

• FAPESP's process: 08/11601-7 - Basic and applied studies of the electrooxidation of glycerol with the purpose of the development of the direct glicerol fuel cell
• Grantee: Vanessa Luciane Oliveira
• Support Opportunities: Scholarships in Brazil - Doctorate