Optimization of the Pd-Fe-Mo Catalysts for Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells

Lee, Y.,Jang, J.,Lee, J.G.,Jeon, O.S.,Kim, H.S.,Hwang, H.J.,Shul, Y.G. Pergamon Press 2016 ELECTROCHIMICA ACTA Vol.220 No.-

Highly active and durable non-platinum catalysts for oxygen-reduction reaction (ORR) have been developed for energy conversion devices such as proton-exchange membrane fuel cells (PEMFCs). In this study, Pd-Fe-Mo catalyst is reported as a non-platinum catalyst for ORR. The atomic ratio and annealing temperatures are controlled on the catalysts to understand interplay between their physical and chemical properties and electrochemical activities. The Pd-Fe-Mo catalyst optimized with 7.5:1.5:1.0 of the atomic ratio and 500<SUP>o</SUP>C of the annealing temperature shows 32.18mAmg<SUP>-1</SUP><SUB>PGM</SUB> (PGM: platinum group metal) of the kinetic current density at 0.9V for ORR, which is comparable to that of commercial Pt/C catalyst. The current density is degraded to 6.20mAmg<SUP>-1</SUP><SUB>PGM</SUB> after 3000 cycling of cyclic voltammetry, but it is greatly enhanced value compared to other non-platinum catalysts. In actual application to PEMFCs, the 20% Pd-Fe-Mo catalyst supported on carbons exhibits a high performance of 506mAcm<SUP>-2</SUP> at 0.6V. The results suggest that the Pd-Fe-Mo catalyst can be a good candidate for non-platinum ORR catalysts.

Highly dispersed and CO_ad-tolerant Pt_shell-Pd_core catalyst for ethanol oxidation reaction: Catalytic activity and long-term durability

Choi, Insoo,Lim, Dong-Hee,Shin, Dong Yun Elsevier 2018 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.43 No.24

<P><B>Abstract</B></P> <P>Highly dispersed Pt<SUB>shell</SUB>-Pd<SUB>core</SUB> catalyst is synthesized via an electroless deposition and a galvanic displacement. From electrochemical analysis, the catalyst is confirmed to be active toward an ethanol oxidation reaction for a prolonged time, and is more resistive against CO<SUB>ad</SUB>-poisoning than a conventional Pt/C catalyst. The stable activity of Pt<SUB>shell</SUB>-Pd<SUB>core</SUB>/C is ascribed to the modified electronic property of Pt over-layer, which leads to a weak CO-adsorption strength with a high affinity for OH. The weakened binding property of surface Pt with CO<SUB>ad</SUB> was experimentally confirmed by conducting a CO<SUB>ad</SUB>-stripping and by measuring an electrochemically active surface area of the catalyst over multiple cycles. The CO<SUB>ad</SUB> oxidation ability of as-synthesized catalyst is further proved by a computational method via density functional theory (DFT) calculation. The result presents a potential application of the catalyst for the efficient ethanol oxidation in a direct ethanol fuel cell.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pt<SUB>shell</SUB>-Pd<SUB>core</SUB>/C catalyst was synthesized by electroless deposition and displacement. </LI> <LI> The catalyst is more active in ethanol oxidation reaction than commercial Pt catalyst. </LI> <LI> The catalyst showed moderate CO<SUB>ad</SUB>-tolerance and long-term durability. </LI> <LI> The stable activity was ascribed to the modified electronic property of the catalyst. </LI> <LI> The higher CO oxidation capacity was supported by density functional theory. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>A Pt<SUB>shell</SUB>-Pd<SUB>core</SUB>/C catalyst was electrochemically synthesized, and exhibited higher catalytic activity with CO<SUB>ad</SUB>-tolerance toward ethanol oxidation at prolonged time. The core-shell configuration induced the change in the binding ability of catalyst with adsorbate, which ultimately increased its CO oxidation capacity.</P> <P>[DISPLAY OMISSION]</P>

Hydrogen Production Through Catalytic Dehydrogenation of Decalin over Pt/C Catalyst Using Activated Carbon Aerogel

Lee, Gihoon,Kang, Ji Yeon,Jeong, Yeojin,Jung, Ji Chul Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.4

To improve its textural properties as a support for platinum catalyst, carbon aerogel was chemically activated with KOH as a chemical agent. Carbon-supported platinum catalyst was subsequently prepared using the prepared carbon supports(carbon aerogel(CA), activated carbon aerogel(ACA), and commercial activated carbon(AC)) by an incipient wetness impregnation. The prepared carbon-supported platinum catalysts were applied to decalin dehydrogenation for hydrogen production. Both initial hydrogen evolution rate and total hydrogen evolution amount were increased in the order of Pt/CA < Pt/AC < Pt/ACA. This means that the chemical activation process served to improve the catalytic activity of carbon-supported platinum catalyst in this reaction. The high surface area and the well-developed mesoporous structure of activated carbon aerogel obtained from the activation process facilitated the high dispersion of platinum in the Pt/ACA catalyst. Therefore, it is concluded that the enhanced catalytic activity of Pt/ACA catalyst in decalin dehydrogenation was due to the high platinum surface area that originated from the high dispersion of platinum.

A study on the CO oxidation reaction by manufacturing methods of room temperature catalysts

김수빈,홍성창 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

A platinum catalyst exhibits excellent CO to CO₂ conversion in room temperature CO oxidation reaction. However, over the course of the reaction time, the catalyst is deactivated by the carbonate formation, so research on the durability enhancement of the catalyst is necessary. In this study, antimony was supported by platinum catalysts in various ways. At this time, all catalysts to which antimony is added have increased CO oxidation removal capability and increase the durability of the catalysts. Accordingly, characteristics of catalysts were observed using various analyses such as FE-TEM, XPS and PL. Active metal particles in the catalyst exhibiting the best reactive activity are found to be very small in size and SMSI effects are produced by increased surface electron density. Therefore, it has been confirmed that the size of active metal particles and SMSI effects act as important factors for the superior efficiency of CO oxidation catalysts at room temperature.

Direct formation of Pt catalyst on gas diffusion layer using sonochemical deposition method for the application in polymer electrolyte membrane fuel cell

Kim, Youngkwang,Karuppannan, Mohanraju,Sung, Yung-Eun,Lim, Taeho,Kwon, Oh Joong Elsevier 2018 International journal of hydrogen energy Vol.43 No.22

<P><B>Abstract</B></P> <P>In this study, the facile and direct formation of platinum catalyst on a carbon paper (gas diffusion layer) via the sonochemical deposition method is demonstrated. An ultrasound irradiation with a carbon paper substrate in a platinum precursor solution formed interconnected platinum grains on the carbon paper surface. The surface morphology and deposition amount of platinum were strong functions of both ultrasound parameters (power and time) and solution composition. The platinum-deposited carbon paper was then directly used as a gas diffusion electrode in PEMFC without adding the ionomer. This exhibited high stability in the accelerated stress test in a single cell operation. The interconnected grains of platinum on carbon paper had high resistance to dissolution in an oxidizing environment and the absence of carbon support also enhanced resistance to carbon oxidation. Although the overall performance did not exceed that of the commercial Pt/C, this approach may be an option to form a stable platinum catalyst for PEMFCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A Pt catalyst was formed directly on a carbon paper via sonochemical deposition. </LI> <LI> The sonochemical deposition formed interconnected grains of Pt on the carbon paper surface. </LI> <LI> The sonochemical deposition condition was optimized for obtaining a uniform Pt catalyst. </LI> <LI> The Pt catalyst/carbon paper showed superior durability to Pt/C in a single cell test. </LI> </UL> </P>

Electrochemical preparation of Pt-based catalysts on carbon paper treated with Sn sensitization and Pd activation

Ahn, Sang Hyun,Choi, Insoo,Kwon, Oh Joong,Lim, Taeho,Kim, Jae Jeong Elsevier 2012 International journal of hydrogen energy Vol.37 No.1

<P><B>Abstract</B></P><P>CoRuPt and CoPtRu catalysts were prepared on carbon paper (CP) using various electrochemical processes including Sn sensitization, Pd activation, Co electrodeposition and galvanic displacement. The Sn–Pd process is a surface treatment that guarantees a larger number of nucleation sites on CP for subsequent Co electrodeposition by modifying the surface to be more hydrophilic. Co particles were deposited on Sn-Pd-treated CP (SCP) by controlling deposition potential and time. Then, Pt and Ru galvanic displacements were performed on the Co particles to form CoRuPt/SCP and CoPtRu/SCP catalysts. Electrochemical measurements confirmed that the CoRuPt/SCP – 1 catalyst with a 1.02 Pt/Ru surface molar ratio showed a peak potential of 741 mV (vs. NHE) for methanol oxidation and 637 mV for carbon monoxide stripping. These values were 80 and 8 mV lower, respectively, than those of a PtRu/C commercial catalyst.</P> <P><B>Graphical abstract</B></P><P>CoRuPt and CoPtRu catalysts were prepared on carbon paper using various electrochemical processes including Sn sensitization, Pd activation, Co electrodeposition and galvanic displacement. The Pt and Ru metals were well dispersed over the Co particles. The synthesized catalysts showed higher catalytic activity in methanol oxidation and greater tolerance against carbon monoxide poisoning compared to a commercial PtRu/C catalyst.</P><P><B>Highlights</B></P><P>▶ CoRuPt and CoPtRu catalysts were prepared on a carbon paper by using electrochemical methods. ▶ Sn–Pd treatment enabled uniform formation of Co with high density. ▶ High wettability of Co surface led well dispersion of Pt and Ru metals over Co particles. ▶ Synthesized catalysts showed higher performance in methanol and carbon monoxide oxidation.</P>

Selective methane chlorination to methyl chloride by zeolite Y-based catalysts

Joo, Hyeonho,Kim, Daeho,Lim, Kwang Soo,Choi, Yong Nam,Na, Kyungsu Elsevier 2018 SOLID STATE SCIENCES Vol.77 No.-

<P><B>Abstract</B></P> <P>The CH<SUB>4</SUB> chlorination over Y zeolites was investigated to produce CH<SUB>3</SUB>Cl in a high yield. Three different catalytic systems based on Y zeolite were tested for enhancement of CH<SUB>4</SUB> conversion and CH<SUB>3</SUB>Cl selectivity: (i) HY zeolites in H<SUP>+</SUP>-form having various Si/Al ratios, (ii) Pt/HY zeolites supporting Pt metal nanoparticles, (iii) Pt/NaY zeolites in Na<SUP>+</SUP>-form supporting Pt metal nanoparticles. The reaction was carried out using the gas mixture of CH<SUB>4</SUB> and Cl<SUB>2</SUB> with the respective flow rates of 15 and 10 mL min<SUP>−1</SUP> at 300–350 °C using a fixed-bed reactor under a continuous gas flow condition (gas hourly space velocity = 3000 mL g<SUP>−1</SUP> h<SUP>−1</SUP>). Above the reaction temperature of 300 °C, the CH<SUB>4</SUB> chlorination is spontaneous even in the absence of catalyst, achieving 23.6% of CH<SUB>4</SUB> conversion with 73.4% of CH<SUB>3</SUB>Cl selectivity. Under sufficient supplement of thermal energy, Cl<SUB>2</SUB> molecules can be dissociated to two chlorine radicals, which triggered the C-H bond activation of CH<SUB>4</SUB> molecule and thereby various chlorinated methane products (i.e., CH<SUB>3</SUB>Cl, CH<SUB>2</SUB>Cl<SUB>2</SUB>, CHCl<SUB>3</SUB>, CCl<SUB>4</SUB>) could be produced. When the catalysts were used under the same reaction condition, enhancement in the CH<SUB>4</SUB> conversion was observed. The Pt-free HY zeolite series with varied Si/Al ratios gave around 27% of CH<SUB>4</SUB> conversion, but there was a slight decrease in CH<SUB>3</SUB>Cl selectivity with about 64%. Despite the difference in acidity of HY zeolites having different Si/Al ratios, no prominent effect of the Si/Al ratios on the catalytic performance was observed. This suggests that the catalytic contribution of HY zeolites under the present reaction condition is not strong enough to overcome the spontaneous CH<SUB>4</SUB> chlorination. When the Pt/HY zeolite catalysts were used, the CH<SUB>4</SUB> conversion reached further up to 30% but the CH<SUB>3</SUB>Cl selectivity decreased to 60%. Such an enhancement of CH<SUB>4</SUB> conversion could be attributed to the strong catalytic activity of HY and Pt/HY zeolite catalysts. However, both catalysts induced the radical cleavage of Cl<SUB>2</SUB> more favorably, which ultimately decreased the CH<SUB>3</SUB>Cl selectivity. Such trade-off relationship between CH<SUB>4</SUB> conversion and CH<SUB>3</SUB>Cl selectivity can be slightly broken by using Pt/NaY zeolite catalyst that is known to possess Frustrated Lewis Pairs (FLP) that are very useful for ionic cleavage of H<SUB>2</SUB> to H<SUP>+</SUP> and H<SUP>−</SUP>. Similarly, in the present work, Pt/NaY(FLP) catalysts enhanced the CH<SUB>4</SUB> conversion while keeping the CH<SUB>3</SUB>Cl selectivity as compared to the Pt/HY zeolite catalysts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Selective chlorination of CH<SUB>4</SUB> with Cl<SUB>2</SUB> molecule was studied using zeolite Y-based catalysts. </LI> <LI> CH<SUB>4</SUB> conversion increased with HY zeolites having acidity, but CH<SUB>3</SUB>Cl selectivity decreased. </LI> <LI> CH<SUB>4</SUB> conversion increased further with Pt/HY zeolites, but CH<SUB>3</SUB>Cl selectivity decreased further. </LI> <LI> Pt/NaY with Frustrated Lewis Pairs improved CH<SUB>4</SUB> conversion and CH<SUB>3</SUB>Cl selectivity simultaneously. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

프로판 탈수소화 반응용 백금촉매의 코크 생성에 미치는 수소비와 주석첨가의 영향

김수영(Soo Young Kim),김가희(Ga Hee Kim),고형림(Hyoung Lim Koh) 한국청정기술학회 2016 청정기술 Vol.22 No.2

코크에 의한 촉매의 불활성화는 산업현장에서 촉매가 사용되는 동안 매우 중요하다. 본 연구에서는 프로판 탈수소 반응을 위한 Pt-Sn 촉매에서 반응조건인 수소의 비율이 코크생성에 미치는 영향과 코크버닝에 의한 촉매 활성의 회복여부, 그리고 코크양에 따른 코크버닝 중의 백금소결여부, Pt-Sn-K 촉매에서 Sn의 함량이 코크생성과 불활성화에 미치는 영향을 확인하고자 하였다. Pt-Sn-K는 Pt와 Sn, K를 순차적으로 각각 θ-알루미나와 γ-알루미나에 담지 하여 제조하였다. 프로판 탈수소 반응은 먼저 반응물중의 수소비를 달리하여 620 ℃에서 수행한 후, 코크버닝을 통해 재생하고 다시 프로판 탈수소 성능을 비교하였다. 재생촉매의 B.E.T 분석과 코크분석, XRD (X-ray diffraction)와 같은 물리분석을 동시에 수행하였다. 촉매의 활성테스트와 특성분석을 통하여 반응물 상에서 수소의 비와 촉매의 Sn함량이 촉매표면의 코크 형성에 영향을 줄 수 있다는 것을 알 수 있다. 또한, 과량의 코크는 Air 재생 과정에서의 백금입자의 소결을 일으키고 촉매의 활성을 저하시킬 수 있다. The loss of activity by coke is an important cause of catalyst deactivation during industrial operation. In this study, hydrogen ratio of reaction condition, which has influenced on coke formation over Pt-Sn catalyst, and regeneration of catalysts activity by coke burning, Pt sintering of coke burning as coke contents, effects of coke formation and deactivation with different Sn contents were confirmed. Pt-Sn-K catalyst supported on θ-alumina and γ-alumina was prepared progressively. Activity of regenerated catalyst for propane dehydrogenation was compared with fresh catalyst by coke burning, after propane dehydrogenation was carried out with different hydrogen ratio at 620 ℃ on fresh catalyst. Regenerated catalyst’s physical characterization such as BET, coke analysis and XRD was investigated. Through catalytic activity test and characterization, Sn contents of catalyst and hydrogen ratio in feed stream could affect coke formation on catalyst surface. Excessive coke makes loss of activity and Pt sintering during air regeneration process.

A Comparative Study on Ternary Low-Platinum Catalysts with Various Constructions for Oxygen Reduction and Methanol Oxidation Reactions

Yan-Ni Wu,Hai-Fu Guo,Peng Hu,Xiao-Peng Xiao,Zhao-Wang Xiao,Shi-Jun Liao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.7

Three types of ternary low-platinum nanocatalysts, alloy PdPtIr/C, core–shell PdPt@PtIr/C and Pd@PtIr/C, have been prepared, and their catalytic behaviors toward methanol oxidation reaction (MOR)/oxygen reduction reaction (ORR) are comparatively investigated via cyclic voltammetry and chronoamperometry analysis in an acidic medium. Through a two-step colloidal technique, the synthesized core–shell structured catalyst PtPd@PtIr/C with alloy core and alloy shell show the best catalytic activity toward MOR and the best poisoning tolerance. The alloy PdPtIr/C catalyst prepared via a one-step colloidal technique exhibits the best performance toward ORR among the three catalysts. All the three catalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and other characterization techniques.

Application of carbon nanotube coated aluminosilicate beads as “support on support” catalyst for hydrogenation of nitrobenzene

László Vanyorek,Ádám Prekob,EmÅke Sikora,Edina Reizer,Gábor Muránszky,Ferenc Kristály,Béla Viskolcz,Béla Fiser 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.79 No.-

Nitrogen-doped bamboo-like carbon nanotube (N-BCNT) coating was synthesized onto the surface ofzeolite beads by using Catalytic Chemical Vapour Deposition (CCVD) method to develop a “support onsupport” (SoS) system. These complex structured materials were used as supports during the preparationof hydrogenation catalysts. Rhodium, palladium and platinum nanoparticles were depositedhomogeneously onto the surface of the N-BCNTs of the SoS (final metal content 2 wt%). The catalyticactivity of these samples was compared in the hydrogenation of nitrobenzene. The Pt/N-BCNT-zeolitesample was the most active (182 mol nitrobenzene after 30 min). The activity of the other two catalysts at20 bar was well below this value, 99.5 mol after 60 min and 96 mol after 120 min for Pd and Rh,respectively. The aniline selectivity was different for the three catalysts and they facilitate the formationof various by-products (e.g. N-methylaniline, cyclohexylamine). The usage of the Pd and Pt/NBCNT-zeolite catalysts are more convenient, as only one main by-product was formed. It was confirmedthat the zeolite supported N-BCNTs are efficient catalyst supports in hydrogenation processes. Furthermore, by using this special SoS structure to support the catalytic metals the applicability iswidened and the catalyst removal is easier.