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Secondary reduction strategy synthesis of Pt-Co nanoparticle catalysts towards boosting the activity of proton exchange membrane fuel cells

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Particuology 2023年第8期79卷 18-26页

作者： Bolong Yang Xiaogang Yu Jingkui Hou Zhonghua Xiang State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical TechnologyBeijing100029China

Based on the volcanic relationship between catalytic activity and key adsorption energies,Pt-Co alloy materials have been widely studied as cathode oxygen reduction reaction(ORR)catalysts in proton exchange membrane fuel cells(PEMFCs)due to their higher active surface area and adjustable D-band energy levels compared to Pt/C.However,how to balance the alloying degree and ORR performance of Pt-Co catalyst remains a great challenge.Herein,we first synthesized a well-dispersed Pt/Co/C precursor by using a mild dimethylamine borane(DMAB)as the reducing agent.The precursor was calcined at high temperature under H_(2)/Ar mixed gas by a secondary reduction strategy to obtain an ordered Pt_(3)Co intermetallic compound nanoparticle catalyst with a high degree of alloying.The optimization of elec-tronic structure due to Pt-Co alloying and the strong metal-carrier interaction ensure the high kinetic activity of the cell membrane electrode.Additionally,the high degree of graphitization increases the electrical conductivity during the reaction.As a result,the activity and stability of the catalyst were significantly improved,with a half-wave potential as high as 0.87 V,which decreased by only 20 mV after 10000 potential cycles.Single-cell tests further validate the high intrinsic activity of the ordered Pt_(3)Co catalyst with mass activity up to 0.67 A mg_(pt)^(-1),exceeding the United states Department of Energy(US DOE)standard(0.44 A mg_(pt)^(-1)),and a rated power of 5.93 W mg_(pt)^(-1).

关键词： Ordered Pt3Co nanoparticle Low platinum catalyst Secondary reduction strategy Oxygen reduction reaction Proton exchange membrane fuel cells

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A pillared-layer metal-organic framework for efficient separation of C_(3)H_(8)/C_(2)H_(6)/CH_(4) in natural gas

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Chinese Journal of Chemical Engineering 2022年第2期35卷 10-16页

作者： Pengtao Guo Miao Chang Tongan Yan Yuxiao Li Dahuan Liu State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical TechnologyBeijing 100029China

Metal-organic frameworks(MOFs)have great potentials as adsorbents for natural gas purification.However,the trade-off between selectivity and adsorption capacity remains a challenge.Herein,we report a pillared-layer metal-organic framework Ni(HBTC)(bipy)for efficiently separating the C_(3)H_(8)/C_(2)H_(6)/CH_(4) mixture.The experimental results show that the adsorption capacity of C_(3)H_(8) and C_(2)H_(6) on Ni(HBTC)(bipy)are as high as 6.18 and 5.85 mmol·g^(-1),while only 0.93 mmol·g^(-1) for CH_(4) at 298 K and 100 kPa.Especially,the adsorption capacity of C_(3)H_(8) at 5 kPa can reach an unprecedented 4.52 mmol·g^(-1) and for C_(2)H_(6) it is 1.48 mmol·g^(-1) at 10 kPa.The ideal adsorbed solution theory predicted C_(3)H_(8)/CH_(4) selectivity is as high as 1857.0,superior to most of the reported materials.Breakthrough experiment results indicated that material could completely separate the C_(3)H_(8)/C_(2)H_(6)/CH_(4) mixture.Therefore,Ni(HBTC)(bipy)is a promising material for separation of natural gas.

关键词： Adsorption Light hydrocarbons Metal-organic framework Natural gas Selectivity Separation

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A dual metal-organic framework strategy for synthesis of FeCo@NC bifunctional oxygen catalysts for clean energy application

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Chinese Journal of Chemical Engineering 2022年第3期35卷 161-168页

作者： Jun Chen Liandong Li Liu Yang Chang Chen Shitao Wang Yan Huang Dapeng Cao State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical TechnologyBeijing 100029China

Developing high efficient bifunctional oxygen electrocatalysts for clean energy applications like Zin-air battery(ZAB)is highly desired,because it would reduce the cost and speed up the practical application of ZAB.Here we use a dual metal-organic framework(MOF)synthesis strategy to prepare the N-doped carbon supported bimetallic FeCo nanoparticle catalysts(marked as FeCo@NC)by pyrolysis of Zn CoZIF/MIL-101(Fe)composite.The FeCo@NC exhibits remarkable electrocatalytic activity for ORR with half-wave potential of 0.89 V vs.the reversible hydrogen electrode(RHE)and robust durability for both ORR and OER(oxygen reduction reaction and oxygen evolution reaction),which is attributed to the generation of Fe_(0.26)Co_(0.74) crystalline phase and mesopores due to the dual-MOF synthesis strategy.The rechargeable ZAB based on FeCo@NC air electrode shows a maximum energy density of139.6 mW·cm^(-2) and excellent cyclic stability over 130 h,significantly surpassing the Pt and Ir-based ZAB.The present work provides a useful dual-MOF synthesis strategy for preparing high-performance multifunctional catalysts for ORR,OER and hydrogen evolution reaction(HER).

关键词： Metal organic Frameworks Zeolite imidazole framework Bifunctional electrocatalysts FeCo alloy Zn-air battery

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d-Orbital steered FeN_(4)moiety through N,S dual-site adjustation for zinc-air flow battery

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Journal of Energy Chemistry 2024年第5期92卷 8-15页

作者： Chunzhu Bao Mingwei Tong Xueli Li Zhonghua Xiang State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical TechnologyBeijing 100029China

The implementation of pristine covalent organic polymer(CO_(2)P)with well-defined structure as air electrode may spark fresh vitality to rechargeable zinc-air flow batteries(ZAFBs),but it still remains challenges in synergistically regulating their electronic states and structural porosity for the great device performance.Here,we conquer these issues by exploiting N and S co-doped graphene with COP rich in metal-ligand nitrogen to synergistically construct an effective catalyst for oxygen reduction reaction(ORR).Among them,the N and S co-doped sites with high electronegativity properties alter the number of electron occupations in the d orbital of the iron centre and form electron-transfer bridges,thereby boosting the selectivity of the ORR-catalysed four-electron pathway.Meanwhile,the introduction of COP materials aids the formation of pore interstices in the graphene lamellae,which both adequately expose the active sites and facilitate the transport of reactive substances.Benefiting from the synergistic effect,as-prepared catalyst exhibits excellent half-wave potentials(E_(1/2)=912 mV)and stability(merely 8.8%drop after a long-term durability test of 50000 s).Further,ZAFBs assembled with the N/SG@CO_(2)P catalyst demonstrate exceptional power density(163.8 mW cm^(-2))and continuous charge and discharge for approximately 140 h at 10 mA cm^(-2),outperforming the noble-metal benchmarks.

关键词： Nitrogen/sulfurdual sites Metal-coordinated nitrogen sites Covalent organic polymer Oxygen reduction reaction Zn-airflow battery

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Catalyst Control of Interfacial Welding Mechanical Properties of Vitrimers

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Chinese Journal of Polymer Science 2022年第6期40卷 611-617页

作者： Zong-Tang Lv Hong-Kun Yang Dong Wang State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical TechnologyBeijing 100029China

Interfacial welding of thermosetting polymers has been a challenge,but vitrimers with dynamic covalent networks open numerous opportunities for welding and adhesion of these materials.In this work,we performed interfacial welding between epoxy-based vitrimers and an epoxy vitrimer and a thermoplastic polyurethane(TPU).Catalyst-controlled interfacial mechanical properties for both the vitrimer/vitrimer and vitrimer/TPU are observed,that is,the more efficient the catalyst for the transesterification reactions,the larger the interfacial fracture energy is,and the better the welding strength will be.The interfacial mechanical properties are also found to be independent of the original mechanical properties of the vitrimers.Even for a vitrimer with poor mechanical properties,both the welded vitrimer/vitrimer and vitrimer/TPU exhibit larger interfacial fracture energy than the one with better mechanical properties as long as the former uses more efficient catalyst.

关键词： Vitrimers Interfacial welding Epoxy Catalyst Thermoplastic polyurethane

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Fluorinated bimetallic nanoparticles decorated carbon nanofibers as highly active and durable oxygen electrocatalyst for fuel cells

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Journal of Energy Chemistry 2022年第10期31卷 549-555,I0014页

作者： Yiming Leng Bolong Yang Yun Zhao Zhonghua Xiang State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical TechnologyBeijing 100029China

The low activity and durability are still the critical barriers for non-precious metal electrocatalyst,mainly involving M-N/C(M=Fe,Co,Mn et al),applied in fuel cell.Constructing bimetallic sites has been explored as an effective method to boost the performance of the catalyst for the synergistic effect between metal atoms.However,this synergistic effect is always suppressed in acidic conditions and results in unstable catalytic performance.Here we create novel fluorinated iron(Fe)and cobalt(Co)bimetallic nanoparticles distributed on nitrogen-doped carbon nanofibers(CNFs)for oxygen reduction reaction(ORR).The fluorination strongly increased the charge density of the bimetallic catalyst and resulted in a remarkable catalytic performance with the half-wave potential of 804 m V in 0.1 M HCl O_(4)and 1.6 times power density improvement for the proton exchange membrane fuel cell device.Importantly,the chemical and mechanical robust CNFs support improved the electric conductivity and stability of bimetallic catalysts,which leads to an ultra-stable electrocatalyst.The fuel cell voltage can keep stable even after 110 h,instead of the continuingly decrease in the traditional M-N/C.

关键词： Bimetallic catalyst Fluorination Electrospinning ORR catalyst PEM fuel cell

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Iron Atom-Cluster Strategy Synthesis of Hierarchically Porous Fe-N-C Catalysts for Proton Exchange Membrane Fuel Cells

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Transactions of Tianjin University 2023年第6期29卷 453-461页

作者： Wenhao Qiu Qing Han Xiaogang Yu Zhonghua Xiang State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical TechnologyBeijing 100029China

Developing nonprecious metal-nitrogen-doped carbon(M-N-C)catalysts with high activity and stability is critical to their widespread use in fuel cells;however,these catalysts still face considerable challenges.Herein,a novel iron atom-cluster strategy for the synthesis of iron-based N-C catalyst comprising Fe nanoparticles(Fe NPs)surrounded by Fe-N_(x) sites is developed for oxygen reduction reactions in an acidic fuel cell.Iron oxide NPs were incorporated into zeolitic imidazolate framework-8(ZIF-8)-derived carbon materials and pyrolyzed at high temperatures using NaCl as a modifi er to produce Fe NPs and Fe-N_(x) composite active sites.The half-wave potential of the optimized Fe_(NP)/FeNC-NaCl material was substantially improved to 0.81 V.Furthermore,even after 15,000 cycles,the half-wave potential of the catalyst remained essentially unchanged.As a cathode catalyst for fuel cells,it realized a high peak power density of 436 mW/cm^(2)under a practical H_(2)-air atmosphere.Therefore,this study presents a new approach for designing and synthesizing electrocatalytic materials with high catalytic activity and stability.

关键词： Oxygen reduction reaction Fuel cell Fe-N-doped carbon Iron atom clusters Pyrolysis synthesis

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Highly efficient electrocatalysts derived from carbon black supported non-precious metal macrocycle catalysts for oxygen reduction reaction

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Journal of Energy Chemistry 2019年第1期28卷 73-78页

作者： Lijie Hou Jianing Guo Zhonghua Xiang State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical Technology

For the sake of accelerating the commercial application of fuel cells, non-noble metal catalysts with high activity and high stability have been widely developed to replace platinum-based catalysts. Here, we report a simple but cost-effective synthetic strategy using iron tetra-amino phthalocyanine(FePC-NH_2)and modified carbon black(HCB) to obtain a novel oxygen reduction electrocatalyst(named as FePCNH_2/HCB-800) with Fe_2O_3 wrapped in nitrogen-doped carbon(N-carbon) as active site. The HCB as template can effectively promotes the formation of Fe_2O_3 active site in the catalysts. Compared to commercial Pt/C catalyst, the Fe PC-NH_2/HCB-800 catalyst exhibits high electrocatalytic activity for oxygen reduction reaction(ORR) with onset potential of 0.98 V and half-wave potential with 0.84 V vs. reversible hydrogen electrode(RHE). Meanwhile, the catalyst also shows excellent circulation stability. We believe that this work provides a platform for ORR and is conducive to the commercialization of fuel cells and metal-air batteries.

关键词： Oxygen reduction reaction Iron tetra-amino phthalocyanine Fuel cell Electrocatalyst

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A review of recent theoretical and computational studies on pinned surface nanobubbles

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Chinese Physics B 2018年第1期27卷 136-144页

作者：刘亚伟张现仁 State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical Technology

The observations of long-lived surface nanobubbles in various experiments have presented a theoretical challenge, as they were supposed to be dissolved in microseconds owing to the high Laplace pressure. However, an increasing number of studies suggest that contact line pinning, together with certain levels of oversaturation, is responsible for the anomalous stability of surface nanobubbles. This mechanism can interpret most characteristics of surface nanobubbles. Here, we summarize recent theoretical and computational work to explain how the surface nanobubbles become stable with contact line pinning. Other related work devoted to understanding the unusual behaviors of pinned surface nanobubbles is also reviewed here.

关键词： surface nanobubble contact line pinning oversaturation lattice density functional theory

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Microdroplet targeting induced by substrate curvature

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Chinese Physics B 2018年第9期27卷 450-456页

作者：张红光郭振江陈珊张博张现仁 State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical Technology

Fundamental understanding of the wettability of curved substrates is crucial for the applications of microdroplets in colloidal science, microfluidics, and heat exchanger technologies. Here we report via lattice Boltzmann simulations and energetic analysis that microdroplets show an ability of transporting selectively to appropriate substrates solely according to substrate shape（curvature）, which is called the substrate-curvature-dependent droplet targeting because of its similarity to protein targeting by which proteins are transported to the appropriate destinations in the cell. Two dynamic pathways of droplet targeting are identified： one is the Ostwald ripening-like liquid transport between separated droplets via evaporating droplets on more curved convex（or less curved concave） surfaces and growing droplets on less curved convex（or more curved concave） surfaces, and the other is the directional motion of a droplet through contacting simultaneously substrates of different curvatures. Then we demonstrate analytically that droplet targeting is a thermodynamically driven process. The driving force for directional motion of droplets is the surface-curvature-induced modulation of the work of adhesion, while the Ostwald ripening-like transport is ascribed to the substrate-curvature-induced change of droplet curvature radius. Our findings of droplet targeting are potentially useful for a tremendous range of applications, such as microfluidics, thermal control, and microfabrication.

关键词： droplet targeting substrate curvature lattice Boltzmann simulation

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