• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3145-3150
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• 2010

Ruthenium catalysts modified by selenium have been introduced as alternative materials to Pt in Direct methanol fuel cells (DMFCs). RuSe nano-particles were synthesized on the Vulcan XC72R carbon supports via polyol method. The prepared catalysts were electrochemically and physically characterized by cyclic voltammetry (CV,) linear sweep voltammetry, methanol tolerance test, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energydispersive Spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). Increasing the Se concentration up to 20 at % increased the electro-catalytic activity for the oxygen reduction. By increasing Se amount, Ru metallic form on the surface was increased. The $Ru_{80}Se_{20}$/C catalysts showed the highest oxygen reduction reaction (ORR) activity and outstanding methanol tolerant property in half cell tests as well as single cell test.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.677-684
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• 2016

Various commercially available gas diffusion layers (GDLs) from different manufacturers were used to prepare an air electrode using $La_{0.8}Sr_{0.2}CoO_3$ perovskite (LSCP) as the catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in an alkaline solution. Various GDLs have different physical properties, such as porosity, conductivity, hydrophobicity, etc. The ORR and OER of the resulting cathode were electrochemically evaluated in an alkaline solution. The electrochemical properties of the resulting cathodes were slightly different when compared to the physical properties of GDLs. Pore structure and conductivity of GDLs had a prominent effect and their hydrophobicities had a minor effect on the electrochemical performances of cathodes for ORR and OER.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.3
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• pp.276-282
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• 2016

The effects of conductive additives in a $La_{0.8}Sr_{0.2}MnO_3$ perovskite bifunctional electrode for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated in an alkaline solution. Highly porous carbon black (CB) and Ni powder were added to the bifunctional electrodes as conductive additives. The surface morphologies of electrodes containing CB and Ni were observed by scanning electron microscopy (SEM). The current densities for both ORR and OER were changed by the addition of CB. The conductive additive changed physical properties of bifunctional electrodes such as the sheet conductance, gas permeability and contact angle. It was observed that the air permeability of electrode was most effective to enhance the currents for ORR and OER.

• Journal of the Korean institute of surface engineering
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• v.51 no.3
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• pp.179-184
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• 2018

In this study, Ni and tungsten carbide (WC) nanoparticles are simultaneously synthesized with the mesoporous carbon nanoparticles (CNP) using a solution plasma processing (SPP) in the benzene. The Ni and WC nanoparticles were formed through the sputtering effect of electrodes during discharge, and mean time CNP were formed through reduction reaction. TEM observation showed that loaded Ni and WC nanoparticles were evenly dispersed on the CNP. The results of electrochemical analysis demonstrated that an introduction of Ni nanoparticles promoted to improve catalytic activity for oxygen reduction reaction (ORR). Moreover, Ni-WC/CNP lead to fast electron transfer process compared to that of WC/CNP. Therefore, the inexpensive Ni-WC/CNP might be a promising as catalytic material for cathodes in fuel cell applications.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.12-18
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• 2012

The prohibitively high cost of Pt catalyst might be the biggest barrier for the commercialization of proton exchange membrane fuel cells (PEMFC) of which wide application is expected. Worldwide research efforts for the development of alternative to Pt oxygen reduction reaction (ORR) catalyst are made recently. One of the important considerations in the catalyst development is durability issue as well as economic aspect. From this point of view, platinum group metals (PGM) except Pt can be a candidate for replacing Pt catalyst because the material properties and the catalytic activity of PGM are expected to be similar to Pt. In contrast to Ir, Rh and Os to which not so much attention has been paid as an ORR catalyst, Pd that is most similar to Pt in terms of material properties and catalytic activity and Ru that is in the form of chalcogenide have been studied intensively. Activity comparison between non-Pt and Pt oxygen reduction catalysts by half cell test using RDE (rotating disk electrode) or PEMFC MEA (membrane electrode assembly) operation indicates that Pd-based catalysts show the most similar activity to Pt. In this paper we analyze the composition of PGM ORR catalyst in literature to promote the development of non-Pt ORR catalyst.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.3
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• pp.260-266
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• 2018

To enhance catalyst activity of the palladium (Pd) towards oxygen reduction reaction (ORR), iridium (Ir) and yttrium (Y) were alloyed by polyol method. Due to the low reduction potential of Y, it is hard to reduce Y ion completely by polyol method. In XPS spectra, the binding energy of the Pd is shifted to a lower value, which indicates the d-electron of Pd is filled by the electron from the Y. And other phases of Y are observed by the XPS. Among the catalysts, the $Pd_4IrY_{0.1}/C$ showed the best activity towards ORR, which indicates the metallic Y is effective for improving the catalytic activity. Thus, for further enhancing ORR activity, the novel method for complete reduction of Y is needed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.5
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• pp.447-452
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• 2008

We synthesized nano-sized $La_{1-x}Sr_xCoO_3$ ($x=0.1{\sim}0.4$) cathode catalyst for the zinc air secondary batteries by citrate method, And we measured the cathode's electrochemical characteristics according to content of strontium compose the cathode catalyst. We controlled the pH of precursor solution by 10 in the process of manufacturing the precursor, We heat treated the prepared precursor at various calcination temperature ($500{\sim}900^{\circ}C$), and examined the optimum calcinations temperature by XRD analysis and electrochemical evaluation. We examined the ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) performance of the prepared $La_{1-x}Sr_xCoO_3$ catalyst powder. When we consider ORR and OER performance simultaneously, $La_{0.7}Sr_{0.3}CoO_3$ catalyst has shown the best performance because of its lowest voltage deference between charge and discharge.

• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.7-14
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• 2017

This study aims to examine the influences of substrates/diffusion layers (DL) and oxygen reduction reaction catalysts ($M_{ORR}$) on the performance of $M_{ORR}/IrO_2$/DL-type bifunctional oxygen electrodes for use in polymer electrolyte membrane (PEM)-type unitized regenerative fuel cells (URFC). The $M_{ORR}/IrO_2$/DL electrodes were prepared via two sequential steps: anodic electrodeposition of $IrO_2$ on various DLs and fabrication of $M_{ORR}$ layers (Pt, Pd, and Pt-Ru) by spraying on $IrO_2/DL$. Experiments using different DLs, with Pt as the $M_{ORR}$, revealed that the roughness factor of the DL mainly determined the electrode performance for both water electrolyzer (WE) and fuel cell (FC) operations, while the contributions of porosity and substrate material were insignificant. When Pt-Ru was utilized as the $M_{ORR}$ instead of Pt, WE performance was enhanced and the electrode performance was assessed by analyzing round-trip efficiencies (${\varepsilon}_{RT}$) at current densities of 0.2 and $0.4A/cm^2$. As a result, using Pt-Ru instead of Pt alone provided better ${\varepsilon}_{RT}$ at both current densities, while Pd resulted in very low ${\varepsilon}_{RT}$. Improved efficiency was related to the additional catalytic action by Ru toward ORR during WE operation.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.406-409
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• 2012

Recently, enormous research efforts have been focused on the development of non-precious catalysts to replace Pt for electrocatalytic oxygen reduction reaction (ORR), and to reduce the cost of proton exchange membrane fuel cells (PEMFCs). In recent years, heteroatom (N, B, and P) doped carbon nanostructures have been received enormous importance as a non-precious electrode materials for oxygen reduction. Doping of foreign atom into carbon is able to modify electronic properties of carbon materials. In this study, nitrogen and boron doped carbon nanostructures were synthesized by using a facile and cost-effective thermal annealing route and prepared nanostructures were used as a non-precious electrocatalysts for the ORR in alkaline electrolyte. The nitrogen doped carbon nanocapsules (NCNCs) exhibited higher activity than that of a commercial Pt/C catalyst, excellent stability and resistance to methanol oxidation. The boron-doped carbon nanostructure (BC) prepared at $900^{\circ}C$ showed higher ORR activity than BCs prepared lower temperature (800, $700^{\circ}C$). The heteroatom doped carbon nanomaterials could be promising candidates as a metal-free catalysts for ORR in the PEMFCs.

• Journal of Electrochemical Science and Technology
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• v.6 no.4
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• pp.121-130
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• 2015

The micro emulsion method has been successfully used for preparing perovskite LaCoO₃ with uniform, fine-shaped nanoparticles showing high activity as electro catalysts in oxygen reduction reactions (ORRs). They are, therefore, promising candidates for the air-cathode in metal-air rechargeable batteries. Since the activity of a catalyst is highly dependent on its specific surface area, nanoparticles of the perovskite catalyst are desirable for catalyzing both oxygen reduction and evolution reactions. Herein, LaCoO₃ powder was also prepared by sol-gel method for comparison, with a broad particle distribution and high agglomeration. The electro catalytic properties of LaCoO₃ and LaCoO₃-carbon Super P mixture layers toward the ORR were studied comparatively using the rotating disk electrode technique in 0.1 M KOH electrolyte to elucidate the effect of carbon Super P. Koutecky-Levich theory was applied to acquire the overall electron transfer number (n) during the ORR, calculated to be ~3.74 for the LaCoO₃-Super P mixture, quite close to the theoretical value (4.0), and ~2.7 for carbon-free LaCoO₃. A synergistic effect toward the ORR is observed when carbon is present in the LaCoO₃ layer. Carbon is assumed to be more than an additive, enhancing the electronic conductivity of the oxide catalyst. It is suggested that ORRs, catalyzed by the LaCoO₃-Super P mixture, are dominated by a 2+2-electron transfer pathway to form the final, hydroxyl ion product.