Renewable energy systems have gained remarkable attention as potential green energy sources with ... more Renewable energy systems have gained remarkable attention as potential green energy sources with escalating energy demand and environmental issues. Direct alcohol fuel cells are potential energy sources with quick start-up, zero emissions, and high power density. However, current electrocatalysts' poor efficiency and catalytic activity hinder their commercialization. In this study, Pd−Nb metal nanoparticles (MNPs) supported on carbon nano-onions (CNOs) were synthesized using the polyol method for the electro-oxidation of isopropanol and ethanol in an alkaline medium. An inexpensive CNO support was synthesized using the soot-based approach. High-resolution transmission electron microscopy analysis confirmed the successful synthesis of CNOs with a quasi-spherical structure and concentric rings resembling an onion. The Fourier transform infrared spectroscopy analysis confirmed the presence of oxygen moieties on the surface of the CNOs, which were used to anchor the MNPs to the surface of the support. The X-ray photoelectron spectroscopy analysis confirmed the composition of the electrocatalysts and the presence of Pd and Nb in different oxidation states. The synthesized Pd−Nb/CNOs exhibited high catalytic activity and stability for isopropyl alcohol and ethanol electro-oxidation. The addition of Nb to Pd reduced the loading of Pd, thus reducing the cost of the electrocatalyst and improving the physicochemical properties and electrocatalytic activity of Pd toward isopropanol and ethanol electro-oxidation. The increased electrocatalytic activity of Pd−Nb/CNOs is attributed to the increased active sites on the surface of the MNPs and the synergistic effects arising from the CNO support and the Pd−Nb MNPs.
Due to their low cost, accessibility of resources, and improved stability and durability, carbon‐... more Due to their low cost, accessibility of resources, and improved stability and durability, carbon‐based nanomaterials have attracted significant attention as cathode materials for oxygen reduction reactions. These materials also exhibit intrinsic physical and electrochemical features. However, their potential for use in fuel cells is constrained by low ORR activity and slow kinetics. Carbon nanomaterials can be functionalized and doped with heteroatoms to change their morphologies and generate a large number of oxygen reduction active sites to lessen the problems. Doping the carbon lattice with heteroatoms like N, S, and P and functionalizing the carbon structure with −OCH3, −F, −COO−, −O− are two of these modifications that can change specific properties of the carbon nanomaterials like expanding interlayer distance, producing a large number of active sites, and enhancing oxygen reduction activity. When compared to pristine carbon‐based nanomaterials, these doped and functionalized ...
Carbon nanofibers (CNFs) supported by Pd and Pd-Sn electro-catalysts were prepared by the chemica... more Carbon nanofibers (CNFs) supported by Pd and Pd-Sn electro-catalysts were prepared by the chemical reduction method using ethylene glycol as the reducing agent. Their physicochemical characteristics were studied using high resolution-transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Bruanaer-Emmett-Teller (BET) analysis. FTIR revealed that oxygen, hydroxyl, carboxylic and carbonyl functional groups facilitated the dispersion of Pd and Sn nanoparticles. The doping of Pd with Sn to generate PdSn alloy was also confirmed by XPS data. The amorphous nature of CNFs was confirmed by XRD patterns which exhibited the Pd diffraction peaks. When Sn was added to Pd/CNFs, the diffraction peaks moved to lower angles. HRTEM images revealed that the CNFs with cylindrical shape-like morphology and also Pd-Sn nanoparticles dispersed on carbon support. The cata...
Carbon nano-onions (CNOs) were successfully synthesized by employing the flame pyrolysis (FP) met... more Carbon nano-onions (CNOs) were successfully synthesized by employing the flame pyrolysis (FP) method, using flaxseed oil as a carbon source. The alcohol reduction method was used to prepare Pd/CNOs and Pd-Sn/CNOs electro-catalysts, with ethylene glycol as the solvent and reduction agent. The metal-nanoparticles were supported on the CNO surface without adjusting the pH of the solution. High-resolution transmission electron microscopy (HRTEM) images reveal CNOs with concentric graphite ring morphology, and also PdSn nanoparticles supported on the CNOs. X-ray diffractometry (XRD) patterns confirm that CNOs are amorphous and show the characteristic diffraction peaks of Pd. There is a shifting of Pd diffraction peaks to lower angles upon the addition of Sn compared to Pd/CNOs. X-ray photoelectron spectroscopy (XPS) results also confirm the doping of Pd with Sn to form a PdSn alloy. Fourier transform infrared spectroscopy (FTIR) displays oxygen, hydroxyl, carboxyl, and carbonyl, which fa...
Renewable energy systems have gained remarkable attention as potential green energy sources with ... more Renewable energy systems have gained remarkable attention as potential green energy sources with escalating energy demand and environmental issues. Direct alcohol fuel cells are potential energy sources with quick start-up, zero emissions, and high power density. However, current electrocatalysts' poor efficiency and catalytic activity hinder their commercialization. In this study, Pd−Nb metal nanoparticles (MNPs) supported on carbon nano-onions (CNOs) were synthesized using the polyol method for the electro-oxidation of isopropanol and ethanol in an alkaline medium. An inexpensive CNO support was synthesized using the soot-based approach. High-resolution transmission electron microscopy analysis confirmed the successful synthesis of CNOs with a quasi-spherical structure and concentric rings resembling an onion. The Fourier transform infrared spectroscopy analysis confirmed the presence of oxygen moieties on the surface of the CNOs, which were used to anchor the MNPs to the surface of the support. The X-ray photoelectron spectroscopy analysis confirmed the composition of the electrocatalysts and the presence of Pd and Nb in different oxidation states. The synthesized Pd−Nb/CNOs exhibited high catalytic activity and stability for isopropyl alcohol and ethanol electro-oxidation. The addition of Nb to Pd reduced the loading of Pd, thus reducing the cost of the electrocatalyst and improving the physicochemical properties and electrocatalytic activity of Pd toward isopropanol and ethanol electro-oxidation. The increased electrocatalytic activity of Pd−Nb/CNOs is attributed to the increased active sites on the surface of the MNPs and the synergistic effects arising from the CNO support and the Pd−Nb MNPs.
Due to their low cost, accessibility of resources, and improved stability and durability, carbon‐... more Due to their low cost, accessibility of resources, and improved stability and durability, carbon‐based nanomaterials have attracted significant attention as cathode materials for oxygen reduction reactions. These materials also exhibit intrinsic physical and electrochemical features. However, their potential for use in fuel cells is constrained by low ORR activity and slow kinetics. Carbon nanomaterials can be functionalized and doped with heteroatoms to change their morphologies and generate a large number of oxygen reduction active sites to lessen the problems. Doping the carbon lattice with heteroatoms like N, S, and P and functionalizing the carbon structure with −OCH3, −F, −COO−, −O− are two of these modifications that can change specific properties of the carbon nanomaterials like expanding interlayer distance, producing a large number of active sites, and enhancing oxygen reduction activity. When compared to pristine carbon‐based nanomaterials, these doped and functionalized ...
Carbon nanofibers (CNFs) supported by Pd and Pd-Sn electro-catalysts were prepared by the chemica... more Carbon nanofibers (CNFs) supported by Pd and Pd-Sn electro-catalysts were prepared by the chemical reduction method using ethylene glycol as the reducing agent. Their physicochemical characteristics were studied using high resolution-transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Bruanaer-Emmett-Teller (BET) analysis. FTIR revealed that oxygen, hydroxyl, carboxylic and carbonyl functional groups facilitated the dispersion of Pd and Sn nanoparticles. The doping of Pd with Sn to generate PdSn alloy was also confirmed by XPS data. The amorphous nature of CNFs was confirmed by XRD patterns which exhibited the Pd diffraction peaks. When Sn was added to Pd/CNFs, the diffraction peaks moved to lower angles. HRTEM images revealed that the CNFs with cylindrical shape-like morphology and also Pd-Sn nanoparticles dispersed on carbon support. The cata...
Carbon nano-onions (CNOs) were successfully synthesized by employing the flame pyrolysis (FP) met... more Carbon nano-onions (CNOs) were successfully synthesized by employing the flame pyrolysis (FP) method, using flaxseed oil as a carbon source. The alcohol reduction method was used to prepare Pd/CNOs and Pd-Sn/CNOs electro-catalysts, with ethylene glycol as the solvent and reduction agent. The metal-nanoparticles were supported on the CNO surface without adjusting the pH of the solution. High-resolution transmission electron microscopy (HRTEM) images reveal CNOs with concentric graphite ring morphology, and also PdSn nanoparticles supported on the CNOs. X-ray diffractometry (XRD) patterns confirm that CNOs are amorphous and show the characteristic diffraction peaks of Pd. There is a shifting of Pd diffraction peaks to lower angles upon the addition of Sn compared to Pd/CNOs. X-ray photoelectron spectroscopy (XPS) results also confirm the doping of Pd with Sn to form a PdSn alloy. Fourier transform infrared spectroscopy (FTIR) displays oxygen, hydroxyl, carboxyl, and carbonyl, which fa...
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Papers by Cyril Selepe