Enhancement of the layered double Perovskite oxides PrBa_0.5Sr_0.5Co_1.5Fe_0.5O5+δ as a Bifunctional catalyst and its Application in Metal-air Battery

( Yunfei Bu ),권오훈,김건태 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Considerable efforts have been devoted to the developing and fabrication of low-cost, precious metal-free electrocatalysts with high performance for the storage of renewable energies. Perovskite, due to its structural and compositional flexibility as well as high intrinsic catalytic activity, has been attracting lots of attentions. Perovskites with large particle sizes synthesized via traditional synthesis routes are suffering from the low mass activities. In this work, double-perovskite PrBa_0.5 Sr_0.5Co_1.5Fe_0.5O5+δ mesoporous nanofiber (PBSCF-F) was prepared via an electrospinng process, which exhibited uniform diameter and high surface areas (near 7.7 times than powders calcined at same temperature), greatly enhancing both of the oxygen reduction reaction and oxygen evolution reaction performance. Benefiting from the unique morphological and superior bifunctional activities, PBSCF-F exhibited remarkable cell performance and exceptionally high stability for hybrid Li-air battery.

A Highly Efficient and Robust Cation Ordered Perovskite Oxide as a Bifunctional Catalyst for Rechargeable Zinc-Air Batteries

Bu, Yunfei,Gwon, Ohhun,Nam, Gyutae,Jang, Haeseong,Kim, Seona,Zhong, Qin,Cho, Jaephil,Kim, Guntae American Chemical Society 2017 ACS NANO Vol.11 No.11

<P>Of the various catalysts that have been developed to date for high performance and low cost, perovskite oxides have attracted attention due to their inherent catalytic activity as well as structural flexibility. In particular, high amounts of Pr substitution of the cation ordered perovskite oxide originating from the state-of-the-art Ba<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>0.8</SUB>Fe<SUB>0.2</SUB>O<SUB>3−δ</SUB> (BSCF) electrode could be a good electrode or catalyst because of its high oxygen kinetics, electrical conductivity, oxygen capacity, and structural stability. However, even though it has many favorable intrinsic properties, the conventional high-temperature treatment for perovskite synthesis, such as solid-state reaction and combustion process, leads to the particle size increase which gives rise to the decrease in surface area and the mass activity. Therefore, we prepared mesoporous nanofibers of various cation-ordered PrBa<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>2–<I>x</I></SUB>Fe<SUB><I>x</I></SUB>O<SUB>5+δ</SUB> (<I>x</I> = 0, 0.5, 1, 1.5, and 2) perovskites <I>via</I> electrospinning. The well-controlled B-site metal ratio and large surface area (∼20 m<SUP>2</SUP> g<SUP>–1</SUP>) of mesoporous nanofiber result in high performance of the oxygen reduction reaction and oxygen evolution reaction and stability in zinc-air battery.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2017/ancac3.2017.11.issue-11/acsnano.7b06595/production/images/medium/nn-2017-06595y_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn7b06595'>ACS Electronic Supporting Info</A></P>

Synergistic interaction of perovskite oxides and N-doped graphene in versatile electrocatalyst

Bu, Yunfei,Jang, Haeseong,Gwon, Ohhun,Kim, Su Hwan,Joo, Se Hun,Nam, Gyutae,Kim, Seona,Qin, Yong,Zhong, Qin,Kwak, Sang Kyu,Cho, Jaephil,Kim, Guntae The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.5

<P>Multifunctional electrocatalysts with high catalytic activity and durability are needed for environmentally clean energy technologies such as water-splitting devices and metal-air batteries. Herein, we investigate a new catalyst, P-3G, consisting of a cation-ordered perovskite (PrBa0.5Sr0.5)0.95Co1.5Fe0.5O5+δ (PBSCF) and 3D porous N-doped graphene (3DNG). This new type of composite electrocatalyst simultaneously exhibited outstanding multifunctional catalytic activities and excellent stabilities for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). A possible mechanism for the synergistic effects between perovskite oxides and 3DNG on ORR, OER and HER was firstly proposed by DFT calculations. The electrocatalytic activity of P-3G appeared to have great potential for a rechargeable Zn-air battery system. The operating voltage differences between the charge and discharge (Δ<I>η</I>) of P-3G and Pt/C-IrO2 after 110 cycles were 0.63 V and 0.87 V, respectively, indicating the substantial durability of P-3G. Moreover, a water-splitting device using P-3G efficiently produced H2 and O2 gases at rates of 0.859 μL s<SUP>−1</SUP> and 0.417 μL s<SUP>−1</SUP>, respectively. This study highlights extended applications of coupled perovskite oxides/carbon materials as versatile electrocatalysts for ORR, OER, and HER and unveils the cause of synergistic interactions between oxide and carbon by DFT calculation.</P>

Low-frequency noise inside metro: contribution analysis and noise control treatment

Yunfei Zhang,Li Li,Zheng Bu,Cunzhen Liu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

Low-frequency interior noise tends to tire passengers and affect their health, the wheel/rail vibration and rolling noise are crucial noise sources. For a metro vehicle, the wheel/rail vibration transmits to the car body through the primary and secondary suspensions, causes the car floor vibration, the wheel/rail rolling noise transmits to carriage. An original study tries to predict low-frequency interior noise and reveal the acoustic law of panel contribution and improve ride comfort combining a wheel/rail rolling noise model, a rigid-flexible vehicletrack coupled dynamic model and detailed car body structural/acoustic finite element models. The results show that, based on the acoustic transfer vector method, the critical element contribution areas to the low-frequency noise were found; after removing the impact of critical elements, the sound pressure level peak at 80 Hz and 110-200 Hz decreased. The thickness increase can improve sound insulation level, but change the lower natural frequency, improve the structure’s stiffness, suppress the amplitude of the transfer function. Based on element contribution analysis, the damping optimization method shows that the global SPL peak decreases by 4.3, 6.4, 7.8, 1.8, 3.5, and 5.2 dB (A,) respectively, from position 1 to 6.

Application of Pt-N doped carbon based catalyst for the outstanding stability for PEMFC

김정원,김창민,( Yunfei Bu ),권오훈,주용완,신지영,김건태 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Platinum (Pt)-based electrodes are the most widely used oxygen reduction reaction (ORR) electrocatalysts in proton exchange electrolyte fuel cell (PEMFC). Although fuel cell using platinum as cathode catalyst has the outstanding performance for ORR, it has plenty of drawbacks, such as CO poisoning effects, high cost of Pt catalyst for commercialization, and unfavorable stability. In this regard, the carbon based electrodes, such as graphene, carbon nanotubes, and carbon black, have been widely investigated in order to overcome the drawbacks of platinum catalysts. In this study, the electrochemical properties and the stability of the advanced Pt-N doped carbon based electrode were reported compared with conventional Pt-based electrodes. As a result, this advanced Pt-N doped carbon based catalyst showed the significantly high stability and electrical performance, 1.7W mg^-1_pt , compared with commercial Pt-based catalyst (Pt/C) , 1.4W mg^-1_pt at 70℃.

3D Flower-Like Hierarchical Ag@nickel-cobalt Hydroxide Microsphere with Enhanced Electrochemical Properties

Zijian Lv,Qin Zhong,Yunfei Bu,Junpeng Wu 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.6

The morphology and electrical conductivity are essential toelectrochemical performance of electrode materials in renewableenergy conversion and storage technologies such as fuel cells andsupercapacitors. Here, we explored a facile method to growAg@nickel-cobalt layered double hydroxide (Ag@Ni/Co-LDHs) with3D flower-like microsphere structure. The results show themorphology of Ni/Co-LDHs varies with the introduction of Agspecies. The prepared Ag@Ni/Co-LDHs not only exhibits an openhierarchical structure with high specific capacitance but also showsgood electrical conductivity to support fast electron transport. Benefiting from the unique structural features, these flower-likeAg@Ni/Co-LDHs microspheres have impressive specific capacitanceas high as 1768 F g−1 at 1 A g−1. It can be concluded that engineeringthe structure of the electrode can increase the efficiency of the specificcapacitance as a battery-type electrode for hybrid supercapacitors.