Papers by Keyword: Oxygen Reduction Reaction

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Authors: Jun Sheng Zheng, Xin Sheng Zhang, Sun Wen, Ping Li, Chun An Ma, Wei Kang Yuan
Abstract: A novel non-metal electrocatalyst based on platelet carbon nanofiber (p-CNF) is prepared, and a palladium electrocatalyst supported on activated carbon (AC) is also synthesized. The physico-chemistry properties of the p-CNF and palladium catalyst on AC (Pd/AC) are investigated by high resolution transmission electron microscopy, N2 physisorption and Raman spectra analysis. From cyclic voltammetric studies, it is found that p-CNF is more active than Pd/AC in acidic media. The p-CNF shows a more positive oxygen reduction reaction (ORR) onset reduction potential and a higher oxygen reduction current density than Pd/AC. Moreover, the ORR is controlled by a surface reaction process when Pd/AC is used, while it becomes diffusion controlled when p-CNF is used.
Authors: Guadalupe Ramos-Sanchez, Fernando Godínez-Salomón, Omar Solorza-Feria, Perla Balbuena
Abstract: Low temperature fuel cells are one of the most promising systems for the transformation of fuels into electricity in an efficient, silent, and environmentally friendly manner. In this paper we show the advances accomplished in the synthesis and a theoretical-experimental analysis of the changes induced by the Ni@Pt structure and the presence of the almost unavoidable NiO species. The synthesis of core-shell nanoparticles is described and then physical and electrochemical characterizations confirm the presence of core-shell nanoparticles with a high electrochemical activity towards the Oxygen Reduction Reaction. Periodic density functional theory calculations are used to analyze the shift in the oxidation potential for Pt, Ni@Pt and NiO@Pt with different number of layers in the shell. The changes in the electrochemical activity towards oxygen reduction are evaluated by allowing oxygen to adsorb on the surface of the nanoparticle and alloys. It is found that only the first and second layers of Pt are being affected by the presence of the Ni or NiO core.
Authors: Akimitsu Ishihara, Shotaro Doi, Yan Liu, Shigenori Mitsushima, Nobuyuki Kamiya, Kenichiro Ota
Authors: Sheng Zhou Chen, Wei Yang, Liang Wei Li, Han Bo Zou, Wei Ming Lin
Abstract: Nitrogen-doped carbon supported Co catalysts (CoNC) were synthesized via condensation reaction of pre-polymer of melamine formaldehyde resin with addition of cobalt nitrate salt, followed by carbonization in nitrogen. Rotating disk electrode technique (RDE) and scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS) were used to identify the structure and oxygen reduction reaction (ORR) kinetics of the catalysts. The results show that the catalysts with 3.77 wt% Co loading yield the best ORR catalytic activity. Koutecky-Levich plots indicate ORR mechanism is governed by mixed mechanisms and the measured electron number varies between 2 and 4. SEM image shows an irregular lamellar structure of CoNC catalyst formed at high temperature, and different Co loadings in CoNC catalyst do not change its surface morphology.
Authors: Lei Ding, Li Xu, Ling Ling Liu, Jin Li Qiao, Yu Yu Liu
Abstract: Effect of heat-treatment on the activity of nickel phthalocyanine (NiPc) catalysts for oxygen reduction reaction (ORR) was studied in both acid and alkaline electrolytes. The catalytic activity was found to depend strongly on the electrolyte and heat treatment temperature. High ORR activity was demonstrated on 40%NiPc/C electrode in 0.1M KOH solution, and the heat-treatment of 800oC is optimal for the catalyst synthesized. Further using rotating disk electrode (RDE) measurements and Koutechy-Levich analysis, the overall electron transfer number in the catalyzed ORR on 40%NiPc/C was found to be 2.8, suggesting the catalyzed ORR proceeds via both the 2e- transfer reduction and the 4e- transfer reduction.
Authors: M.T. Nguyen, A. Iannaci, B. Mecheri, I. Luisetto, A. d’Epifanio, S. Licoccia
Abstract: Novel electrocatalysts from iron phthalocyanine (FePc) and polyindole (PID) supported on carbon nanotubes (CNTs) have been synthesized for oxygen reduction reaction (ORR) in Direct Methanol Fuel Cell (DMFC). Two synthetic strategies have been proposed: i) preparation of PID on CNTs (PID/CNTs) through indole polymerization followed by the mechanical mixing of PID/CNTs with FePc (FePc_PID/CNTs); and ii) dispersion of polymerized PID, FePc, and CNTs in methanol and subsequent drying (FePc/PID/CNTs). The morphology of prepared catalysts was examined by SEM, and the electrochemical activity towards ORR was evaluated by cyclic voltammetry. FePc/PID/CNTs catalysts were found to have higher activity than that of FePc_PID/CNTs, due to a better dispersion of PID and FePc on carbon support, as demonstrated by SEM. Furthermore, in comparison with platinum on carbon black the prepared PID-based catalysts exhibited a stable ORR potential in both H2SO4 and H2SO4 + CH3OH solution. These new iron-based catalysts are thus promising to substitute platinum/carbon black at the cathode side of DMFC.
Authors: S. Mentus, Ivan Krstić, Ž. Tešić, Amelia Montone
Abstract: Potentiodynamic polarization of a mechanically polished titanium electrode in a diluted solution of Rhodium(III) chloride in 0.1 M perchloric acid was performed, resulting in simultaneous formation of both Rh and TiO2 films. The morphology of obtained Rh/TiO2 composite film followed the morphology of titanium support, as evidenced by SEM technique. This composite surface was examined by cyclic voltammetry in both acidic and alkaline solutions, in the potential region of both hydrogen and oxygen underpotential deposition. The charge related to hydrogen underpotential deposition corresponded to a surface roughness of 43. As a consequence of high surface roughness, the diffusion current of oxygen reduction in an oxygen saturated 0.1 M NaOH solution, measured by voltammetry on rotating disc electrode, was found to be comparable to the current of hydrogen underpotential deposition.
Authors: Yi Li, Juan Yang, Kai Xu
Abstract: High platinum requirements in electrocatalyst bring about huge expenditure, which hinders the commercialization and wide adoption of proton electrolyte membrane fuel cells (PEMFCs). Therefore, developing new fuel cell catalysts with excellent oxygen reduction reaction (ORR) performance may be a potential way to solve this drawback. In this paper, a facile ultrasonic-assisted method is introduced to synthesize bimetallic PtCo nanoparticles supported on three-dimensional reduced graphene oxide (Pt-Co/3DrGO). Results indicate that PtCo nanoparticles with alloy structure, small size (12.4 nm), and uniform distribution are well-dispersed onto rGO sheets. With 3D porous structure, the fabricated Pt-Co/3DrGO catalyst exhibits better ORR activity and long-term stability than that of commercial Pt/C (20 wt%). The increased electrocatalytic activity is attributed to the formation of 3D porous structure together with the effective surface structure and the highly uniform distribution of the PtCo alloy nanoparticles on rGO sheets.
Authors: Jing Yan Chen, Xiao Guang He, Hai Yan Qi, Hao Chen Shi, Feng Gao
Abstract: Non-precious metal Fe-C-N thin films were prepared by magnetron sputtering at different sputtering currents applied on a Fe target. The films were subsequently heated at 700 °C in N2 atmosphere. Fe-C-N thin films were investigated as an alternative cathode catalyst for the oxygen reduction reaction (ORR) in a neutral solution. The results indicated that the catalytic activity of Fe-C-N thin films for the ORR increased with the increase of the sputtering current. When the sputtering current was 0.2 A, limiting current density was 5.50 mA cm-2 and onset potential was-0.10 V vs. Ag/AgCl, which were comparable with those of commercial Pt/C catalysts. The current density of films was unchanged in 5000 seconds in the chronoamperometric experiment, indicating that the catalytic activity was very stable in a neutral solution for potential use in microbial fuel cells.
Authors: Shi Qiang Chen, Dun Zhang, Jia Jia Wu
Abstract: Different from the corrosion under anaerobic conditions, oxygen (O2) takes part in the cathodic reaction under aerobic conditions. Sulfate-reducing bacteria (SRB) have been regarded for many years as strictly anaerobic bacteria, but recently, they are found to be able to survive in the presence of O2, and how they affect the oxygen reduction reaction (ORR) has not been clear. In this study, the role of sulfide, a key inorganic metabolite of SRB, in ORR has been investigated on Q235 carbon steel electrode with cyclic voltammetry and electrochemical impedance spectroscopy. Three cathodic processes are recorded on cyclic voltammograms in O2-saturated 3.5% NaCl solution: ORR, iron oxides reduction and hydrogen evolution. The peak current of ORR decreases with the introduction of sulfide, and finally vanishes when the sulfide concentration is more than 0.5 mM. EIS reveals that sulfide leads to the disappearance of the feature of semi-infinite diffusion of ORR and the fitting results demonstrate that charge transfer resistance increases with increasing sulfide concentration. Therefore sulfide hinders the cathodic reduction of O2 on Q235 carbon steel in 3.5% NaCl solution.
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