• Korean Journal of Materials Research
• /
• v.28 no.11
• /
• pp.646-652
• /
• 2018

During a long-term operation of polymer electrolyte membrane fuel cells(PEMFCs), the fuel cell performance may degrade due to severe agglomeration and dissolution of metal nanoparticles in the cathode. To enhance the electrochemical durability of metal catalysts and to prevent the particle agglomeration in PEMFC operation, this paper proposes a hybrid catalyst structure composed of PtCo alloy nanoparticles encapsulated by porous carbon layers. In the hybrid catalyst structure, the dissolution and migration of PtCo nanoparticles can be effectively prevented by protective carbon shells. In addition, $O_2$ can properly penetrate the porous carbon layers and react on the active Pt surface, which ensures high catalytic activity for the oxygen reduction reaction. Although the hybrid catalyst has a much smaller active surface area due to the carbon encapsulation compared to a commercial Pt catalyst without a carbon layer, it has a much higher specific activity and significantly improved durability than the Pt catalyst. Therefore, it is expected that the designed hybrid catalyst concept will provide an interesting strategy for development of high-performance fuel cell catalysts.

• Clean Technology
• /
• v.29 no.4
• /
• pp.313-320
• /
• 2023

In order to increase the usability of H₂-SCR, the NOx removal characteristics with catalyst powder of PtNi/CeO₂-W-TiO₂ using Ce as a co-catalyst was synthesized and coated on a porous metal structure (PMS) were evaluated. Catalyst powder of PtNi/CeO₂-W-TiO₂(PtNi nanoparticles onto W-TiO₂, with the incorporation of ceria (CeO₂) as a co-catalysts) was synthesized and coated onto a porous metal structure (PMS) to produce a Selective Catalytic Reduction (SCR) catalyst. H₂-SCR with CeO₂ as a co-catalyst exhibited higher NOx removal efficiency compared to H₂-SCR without CeO₂. Particularly, at a 10wt% CeO₂ loading ratio, the NOx removal efficiency was highest at 90℃. As the amount of catalyst coating on PMS increased, the NOx removal efficiency was improved below 90℃, but it was decreased above 120℃. When the space velocity was changed from 4,000 h^-1 to 20,000 h^-1, the NOx removal efficiency improved at temperatures above 120℃. It was expected that the use of the catalyst could be reduced by applying the PMS with excellent specific surface area as a support.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.781-781
• /
• 2009

We demonstrate that trasition metal catalyst nanoparticle (NP) attached to carbon nitride nanotubes (CNNTs) show selective catalytic activities on hydrogen generation from the water solution including chemical hydride negative ions. The natural bonding orbitals (NBO) obtained from the first-principle calculations shows that the catalysts attached on CNNTs are quite differently polarized when they play for hydrogen generation from chemical hydride ions and hydrogen of water. For Co and Ni nanoparticles attached on CNNTs, their charges are more positively polarized when they interact with $BH_4^-Na^+$ and $H_2O$ while Pt atoms are less positively charged. In this matter, the increased positive charges on catlyst nanoparticles are proven to be more efficient in attracting hydride negative ions, thus improving hydrogen generate rates. Consequently, this result implies that these different charge polarization leads to selective catalytic activities of NPs-CNNTs. In the hydrogen generation experiments, Co-CNNTs shows the highest hydrogen generation rate when the similar amounts of catalyst nanoparticles (Co, Ni, and Pt) are dispersed on the sidewalls of CNNTs.

• Clean Technology
• /
• v.30 no.1
• /
• pp.62-67
• /
• 2024

In this study, an alkali metal Na was introduced into iron-based catalysts used in the carbon dioxide-based Fischer-Tropsch process by wet impregnation and physical mixing methods to compare their performance. The as-prepared catalysts were evaluated for reactivity at 3.5 MPa, 330 ℃, feed ratio of H₂/CO₂ = 3 with a space velocity of 4,000 mL h^-1 g_cat^-1. Comparing the two catalysts, it was found that Na was uniformly distributed throughout the catalyst when wet-impregnated, but Na for physically mixed catalyst was relatively located on the surface of the catalyst. In addition, the wet-impregnated catalyst showed higher liquid hydrocarbon (C₅₊) yield and lower CO selectivity. In conclusion, the effect of Na distribution in the catalyst on the reaction was identified and can be controlled by the introduction method.

• Journal of the Korean Applied Science and Technology
• /
• v.30 no.4
• /
• pp.726-739
• /
• 2013

Fischer-Tropsch synthesis (FTS) converts synthesis gas (CO and $H_2$) into longer chain hydrocarbons by a surface polymerization reaction. Cobalt- or iron-based catalysts normally show excellent activity for syngas conversion to petroleum products leading to super clean diesel fuels. The catalytic activities of the catalysts in FTS depend on the number of active sites on the surface. The number of active site was determined by the active metal particle size, loading amount, reduction degree and support-active metal interaction. The investigation adopts new methodology in preparing FT catalyst, which contains the controlled synthesis of active metal. The main focus of this paper is to give an overview of the types of catalysts, also including their preparation and reduction; the types of FT reactors; and also including the reaction conditions.

• Transactions of the Korean hydrogen and new energy society
• /
• v.27 no.5
• /
• pp.471-477
• /
• 2016

In this research, the Ir supported $TiO_2$ (P25) catalyst was prepared by precipitation method for oxygen evolution reaction. The $Ir/TiO_2$ catalyst was synthesised by reduction reaction using reducing agent. Physiochemical characterizations of synthesized $Ir/TiO_2$ catalyst was studied by means of SEM, EDS mapping, TEM and XRD. The Electrochemical characterizations were tested by using the technique of CV and LSV by RDE and Potentiostat. Physicochemical properties were characterized with XRD where Iridium metal morphology and Ir(111) and Ir(222) peaks were founded. $Ir0.2Ru0.8O_2$ exhibited higher OER activity than $Ir0.5Ru0.5O_2$ followed by $Ir/TiO_2$ and $IrO_2$.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.12
• /
• pp.1310-1314
• /
• 1998

The oligo(methylsilene) (1) was treated with the group 4 metallocene Cp2MCl2/Red-Al (M = Ti, Zr, Hf) combination catalysts and with the group 6 metal carbonyl M(CO)6 (M = Cr, W) catalysts, producing the modified, cross-linked polymers. The average molecular weights and percent ceramic residue yields of modified polymers increase as the catalyst goes down from Ti to Hf and similarly as the catalyst goes down from Cr to W. An interrelationship between average molecular weights and percent ceramic residue yield is found within the respective group of catalysts, but is not observed as the catalyst goes down from Ti to W. The polymers modified with the group 4 metallocene combination catalysts have higher molecular weights and similar percent ceramic residue yields as compared to the polymers modified with the group 6 metal carbonyl catalysts. The catalytic activities of group 4 metallocene combinations appear to be higher -100 ℃, but to be lower at very high temperature than those of group 6 metal carbonyls.

• Journal of the Korean Chemical Society
• /
• v.42 no.6
• /
• pp.696-702
• /
• 1998

The effect of alkali metal salt on the activity of Co-Mo catalyst which has high resistance to sulfur poisoning for water gas shift reaction(WGSR) was studied. Two groups of catalysts were prepared to investigate the effects of anion and cation in alkali metal salts. For K-doped catalysts made with various potassium salts having different anion, the catalytic activity was explained to depend mainly on the BET surface area. Among the catalysts prepared by various nitrates of alkali metal as precursor, the Li-doped catalyst showed the best activity, and the others did not make significant differences giving relatively low activities. And the change of BET surface area by varying the loading of alkali metal showed a similar trend to that of activity. In this case, the activity was dependent on both BET surface area and the ratio of $Mo^{6+}$ with a tetrahedral coordination symmetry to $Mo^{6+}$ with an octahedral one, $Mo^6+[T]/Mo^{6+}[O]$ value.

• Journal of the Korean Institute of Gas
• /
• v.13 no.5
• /
• pp.33-38
• /
• 2009

Synthetic natural gas was producd by the reaction of carbon monoxide and hydrogen via methanation. Ni-Co bimetallic catalyst supported on $Al_2O_3$ for methanation was prepared using deposition-precipitation method. For the comparison, Ni, Co monometallic catalyst was prepared using the same method. The prepared catalysts were characterized by TEM, XRD and TPR and applied to methanation reaction. The catalysts prepared using deposition-precipitation method showed the high metal dispersion. The activity of Ni-Co bimetallic catalyst was higher than that of Ni, Co monometallic catalyst. TPR measurements indicated that Ni-Co bimetallic catalyst had more active hydrogen species than Ni, Co monometallic catalyst due to the synergetic effect in the presence of Ni and Co.

• Journal of Industrial and Engineering Chemistry
• /
• v.68
• /
• pp.335-341
• /
• 2018

We report the catalytic effects of metal oxides on the $CO_2$ absorption rate in an aqueous potassium salt of ${\text\tiny{L}}-lysine-HCl$ using the vapor liquid equilibrium method. The best $CO_2$ absorption rate obtained through testing metal oxides in a highly concentrated potassium salt of amino acids (2.0 M) was identified using CuO. The recyclability of the metal oxides was tested over three cycles. The catalyst CuO was found to enhance the absorption rate of $CO_2$ by 61%. A possible mechanism was proposed based on NMR spectroscopy studies. Further, the effect of change in liquid absorbent viscosity on $CO_2$ absorption is discussed.