共价有机框架材料(COFs)在氧电极电催化中的研究进展

在碳达峰、碳中和的目标之下,燃料电池、金属-空气电池、电解水等清洁能源技术提高了能源利用率,在未来将成为新的能源消费方式.氧还原反应(ORR)、氧析出反应(OER)因其缓慢的动力学过程而导致此类清洁能源技术的发展受到阻碍.贵金属催化剂虽被认为是最高效的催化剂,但其成本高、稳定性低,寻找非贵金属催化剂已成为相关研究的趋势.共价有机框架材料(COFs)作为一类新兴的材料,由有机单体通过特殊的共价键连接而成,因其具有可调控的结构、低密度、高稳定性、较大比表面积等独特的优点,通过合理的设计策略,将其应用于电催化剂的研究在近年来逐步兴起.本文回顾了近期适用于ORR、OER及ORR/OER双功能电催化的二维COFs(2D COFs)材料,主要介绍了以纯COFs作为电催化剂、COFs与其他材料形成复合结构、COFs热解碳化等策略制备高效电催化剂,并从分子设计及电子调控等层面上梳理了上述策略对电催化活性中心的形成或电催化活性提升的原因,对当前存在的问题提出总结,以期在今后的研究中起到一定借鉴意义.     

微波合成碳载铂用于氧还原电催化

质子交换膜燃料电池阴极氧还原反应(ORR)动力学迟缓,因此,开发高活性、低成本的ORR电催化剂对燃料电池发展具有重要意义。本文利用微波法,在氢氧化钠/乙二醇的溶液中还原氯铂酸合成了铂纳米颗粒(Pt NPs);随后,将其与Vulcan XC-72R炭黑混合,制备了高分散性的碳载铂(Pt/C)催化剂。透射电镜结果表明,Pt NPs在炭黑表面均匀分布,平均粒径约为2.8 nm,略小于商业Pt/C催化剂(约3 nm)。进一步,探究了微波功率、分散溶剂以及载碳时有或无HCl对制备催化剂分散性和氧还原活性的影响。电化学测试表明,相较于商业Pt/C催化剂,优化的微波Pt/C催化剂展现出更为优异的ORR催化活性。在0.1 mol/L HClO₄电解液中,微波Pt/C催化剂的半波电位较商业Pt/C催化剂高出9 m V,其在0.9 V (vs. RHE)处的质量活性和面积活性为0.109 A/mg和0.127 mA/cm²,均分别高于商业Pt/C催化剂的0.093 A/mg和0.118 m A/cm²。此外,微波Pt/C催化剂具有比商业Pt...     

单原子催化剂在氢燃料电池阴极氧还原反应中的研究进展

氢燃料电池是一种高效、环境友好以及零碳排放的能量转化技术,然而高成本的贵金属催化剂阻碍了其规模化应用。单原子催化剂因具有高原子利用率、高催化活性和选择性、低成本等优点,对氧分子表现出优异的催化还原性能,在氢燃料电池中具有广阔的应用前景。如何设计合成高效和低成本的单原子催化剂成为该领域的研究热点。重点综述贵金属单原子催化剂和非贵金属单原子催化剂在氢燃料电池阴极氧还原反应中的研究进展,总结提出增强单原子催化剂氧还原性能的调控策略,包括配位结构、局域环境、双原子对、缺陷位点以及暴露活性位点等调控机制,为从原子尺度设计高效氧还原催化剂提供了思路借鉴,并对氢燃料电池氧还原单原子催化剂的发展机遇与挑战进行了展望。     

电化学氧还原反应合成H2O2碳基催化剂研究进展

电化学氧还原反应(ORR)合成H2O2是一种低成本、无污染的绿色合成方法.但是,ORR动力学缓慢,存在四电子ORR生成H2O的竞争反应,因此需要使用催化剂提升ORR的反应活性以及二电子ORR的选择性.近年来,碳基材料因价格便宜、来源广泛、调控方法多样,被广泛应用于该领域.本文首先简要介绍了电催化ORR合成H2O2的机理,并根据机理分析了影响电化学合成H2O2催化性能的关键因素.接着阐述了提升碳基ORR催化剂活性与二电子选择性的策略,并着重介绍了非金属原子掺杂碳材料和过渡金属氮碳材料.最后,总结了碳基催化剂在电化学合成H2O2中存在的问题和面临的挑战,对碳基催化剂在电合成H2O2中应用的发展趋势进行了展望.     

TiO2纳米纺锤体负载Pt在氧还原反应中的应用

燃料电池中催化剂的稳定性是影响其实际应用的关键问题之一。本研究合成了锐钛矿型纺锤状TiO₂纳米材料,并负载纳米Pt制备了TiO₂-Pt双组分复合催化材料。将其制作成电极材料后,进行了TEM、XRD、拉曼光谱、电化学特性分析。结果表明：TiO₂-Pt材料中Pt纳米颗粒的TEM形貌与TiO₂的表面亲和力有关;该双组分催化剂呈现出两个单独的氧还原反应（ORR）峰;在负载Pt后,材料电荷传输电阻明显减小,使得TiO₂-Pt中TiO₂纺锤体组分上的ORR性能明显增强;紫外光可同时促进TiO₂-Pt中两组分的ORR性能;TiO₂-Pt比炭黑负载Pt具有更好的稳定性。     

氮/磷共掺杂生物质基氧还原催化剂的制备与阴极性能研究

文章以废弃物榴莲壳作为原料,以(NH4)3PO4·3H2O作为掺杂源,同时引入N和P两种非金属元素,制备了N/P共掺杂氧还原催化剂.实验结果表明,当煅烧温度为900℃时,所得催化剂NPDC-900具有大量的介孔结构,比表面积可达到1264 m2/g,预测该催化剂具有较高的活性位点利用率和优异的传质效率.中性环境中的氧还...     

当前实用和未来发展Pt-非Pt氧还原电催化剂研究进展

燃料电池阴极侧氧还原反应由于其迟缓的动力学,使得贵金属铂成为最为高效的电催化剂,成本高昂,限制燃料电池规模化应用。开发低成本、高性能、可实用氧还原电催化剂尤为重要。基于课题组多年在实用化燃料电池氧还原电催化剂的研究情况,综述面向当前实用和未来发展的铂-非铂电催化剂的研究进展。重点介绍实用化高载量、高活性、高结构稳定性铂基电催化剂合成策略以及在燃料电池膜电极中的性能高效表达,同时阐述非铂碳基催化剂理性设计、可控制备。此外,对该研究方向的发展进行展望,以期加速燃料电池关键材料国产化。     

限域型贵金属氧还原反应电催化剂研究进展北大核心CSCD

开发高效的氧还原反应电催化剂是实现质子交换膜燃料电池规模化应用的关键技术之一。目前常用的贵金属催化剂成本较高,并且稳定性仍需改善。物理限域是改善催化剂稳定性的有效策略,在不影响贵金属催化剂催化活性的前提下,物理限域层不仅可以抑制催化剂的烧结,还能够减少催化剂在反应过程中的团聚、脱落以及溶解等问题,从而提升催化剂的寿命。本文回顾了近年来用于电催化氧还原反应的限域型贵金属催化剂,主要包括导电聚合物限域、非金属氧化物限域、金属氧化物限域以及碳层限域的贵金属催化剂。根据限域层制备策略不同,重点分析了限域层的孔结构、导电性、致密性、抗腐蚀性与催化剂性能之间的构效关系。着重介绍了实现碳层限域的三种策略,包括“沉积-转化”、“嵌入-转化”以及“一步热解”。分析表明,通过构筑具有丰富孔结构、高导电性及合适厚度的限域层能够在保证活性的同时显著提升催化剂稳定性。最后对全文进行了总结并对当前存在的问题进行了整理,同时对未来限域型催化剂的发展进行了展望。     

双金属Ni-Co基析氧反应电催化剂研究进展

目的  能源消耗的持续增长和化石燃料燃烧带来的环保和能源安全问题已经引起世界各国的广泛关注。因此,发展清洁能源生产技术已成为世界范围内的主要研究重点。氢能具有无污染、比能密度高、资源丰富等特点,是最具潜力的传统化石燃料替代品之一。电催化分解水被认为是最有希望的制氢方法,但阳极上的析氧反应动力学缓慢,能量转换效率低,是大规模制氢的主要瓶颈。与稀有和昂贵的贵金属催化剂相比,镍-钴（Ni-Co）基电催化剂由于具有可调的电子结构、高导电性和低成本优势,有望在碱性溶液中实现卓越的OER活性和耐久性。 方法  文章总结并讨论了在OER中Ni-Co基电催化剂的最新研究发展。重点讨论了Ni-Co基电催化剂的设计和合成,以及在OER过程中提高其电催化性能的研究策略。 结果  为了代替钌、铱等贵金属催化剂,研究者们对Ni-Co基非贵金属催化剂进行了大量研究。包括氧化物、氢氧化物、合金、氮化物、硫化物、磷化物等在内的多种Ni-Co基催化剂通过化学结构的调控,从阳极角度提高了电催化制氢的活性。但这些催化剂又分别面临不同的缺陷,有待进一步研究克服。 结论  开发具有高OER活性的非贵金属催化剂是降低电解水制氢成本,促进氢能产业发展的重要途径。虽然仍有一些技术问题尚未解决限制了Ni-Co基催化剂替代贵金属催化剂,但作为重要的贵金属催化剂替代品,Ni-Co基催化剂的研究为新型催化剂的开发提供了重要选择。     

二维碳载Au4Pd2催化剂的构建及其电催化性能

贵金属纳米团簇由于精确的结构和明确的化学组成而受到广泛的关注.该工作采用具有精准的颗粒大小和精确的结构双金属金属纳米团簇,研究其电子结构、几何结构对催化反应的影响,同时利用杂原子与主原子间的强电子耦合作用调控催化性能.首先制备4个金原子与2个钯原子组成的金钯纳米团簇,并分散至二维材料上得到单团簇分散的金钯基纳米复合材料催化剂;通过XPS测试可知,AuPd与载体之间存在较强的协同作用,有助于促进其氧还原(ORR)与析氢反应(HER)的稳定性;调节贵金属比例得到最佳比例的金钯催化剂,在0.1 mol/L KOH氧饱和电解液中,起始电位为0.95 V,半波电位为0.81 V,其ORR性能优于商业Pd/C.该催化剂也具有良好的HER性能,在0.5 mol/L H2SO4电解液中,电流密度为10 mA/cm2下的过电位为129 mV;利用X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电镜(TEM)对催化剂结构进行表征分析,解释其结构与性能间的联系.优化贵金属团簇掺杂比例得到具有优异氧还原与析氢性能的双功能催化剂,为高效稳定的电催化剂的开发提供了新方向.     

Heteroatom (B,N and P) doped porous graphene foams for efficient oxygen reduction reaction electrocatalysis

Heteroatoms (B, N and P) doped porous graphene foams are developed via a hard-templating method. We use boric acid as the precursor of boron source, triphenylphosphine as precursor of phosphorus source, cyanamide as the precursor of nitrogen source and ferrous chloride as the precursor of transition metal to synthesize a series of transition metal iron-modified multi-element doped porous graphene foams catalysts. Our results showed that heteroatoms (B, N and P) doped porous graphene foams exhibited excellent ORR performance. The most efficient one, i.e., PGF-Fe-NBP, received the onset potential of 0.95 V and a half-wave potential of 0.84 V in alkaline medium. Even in acidic medium, PGF-Fe-NBP received the onset potential of 0.85 V and a half-wave potential of 0.68 V. In addition, it also obtained superb electro activities of low H₂O₂% and high electron transfer number in both alkaline and acidic medium. Moreover, we found that iron modification can promote doping amount of heteroatoms and increase the degree of graphitization to form a relatively larger specific surface area for more active sites, thus improving the ORR performance of heteroatoms (B, N and P) doped porous graphene foams. Meanwhile, we systematically compare multi-element doping with that of single-element doping and dual-element doping.     

Co-Fe/MIL-101(Cr) hybrid catalysts: Preparation and their electrocatalysis in oxygen reduction reaction

The development of highly efficient electrocatalysts with low cost for oxygen reduction reaction (ORR) is urgently required for metal-air batteries and fuel cells. In this work, FeCo/MIL-101(Cr) with various molar ratios of Fe/Co as hybrid catalysts was prepared by a facile and mild impregnation method. MIL-101(Cr) increased the specific surface areas of the hybrid catalysts, thus improving the dispersion of Fe and Co species at their surfaces. The effects of Fe and Co species on ORR activity of the hybrid catalysts were investigated. It is found that the synergistic effects between the well-dispersed Fe and Co species contribute mainly to ORR activity. More specifically, Fe species exert a partial-charge-transfer-activation effect on Co ones, which reduces the charge transfer resistance and thus improves the catalytic activity. As a result, FeCo/MIL-101(Cr) showed the excellent ORR activity, in which Co₅₀Fe₅₀/MIL-101(Cr) exhibited the superior ORR activity to the other prepared hybrid catalysts.     

Self-supporting one-dimensional ZnFe-BDC for electrocatalysis oxygen evolution reaction in alkaline and natural seawater

The morphology and overall electronic structure of the metal-organic framework (MOF) can be regulated by introducing non-noble metal elements so that it has higher electrocatalytic oxygen evolution reaction (OER) activity but does not change the stability of MOF itself. Herein, we report a series of self-supporting ZnFe bimetallic MOF electrocatalysts on foam nickel (NF) substrates using a simple one-step solvothermal strategy. The morphology evolution process and electronic structure of the Zn²⁺/Fe³⁺ molar ratio from 0.25 to 0.75 are systematically investigated. It is worth noting that the overpotentials of ZnFe-BDC-0.75 in alkaline freshwater electrolyte and natural seawater electrolyte are 292 mV and 308 mV (100 mA cm^?2), respectively. This work emphasizes the significance of tailoring the electronic microstructure of bimetallic MOFs for efficient OER activity in alkaline and seawater.     

Facile synthesis of laminated porous WS2/C composite and its electrocatalysis for oxygen reduction reaction

The Vulcan XC-72R modified WS₂ nanocomposite (WS₂/C）was prepared by solid reaction process combined with sonication. The as-prepared WS₂/C nanocomposite presents a laminated porous structure by SEM and TEM characterization. The electrochemical experiments show that the onset potential and the limiting-current density of WS₂/C is 0.78 V and 4.99 mA cm^?2, respectively, which is much higher than, WS₂ (3.12 mA cm^?2) and Vulcan XC-72R (2.79 mA cm^?2). The number of transfer electrons in ORR at the WS₂/C nanocomposite electrode is 3.70, which is close to four-electron process. Besides, the current density of WS₂/C nanocomposites remained at 90% after 20,000 s, indicating its superior electrochemical stability. All these facts reveal that the as-prepared WS₂/C nanocomposite can be regarded as a promising cathode ORR catalyst for fuel cell.     

Graphite-nanofiber-supported porous Pt-Ag nanosponges: Synthesis and oxygen reduction electrocatalysis

A facile synthesis method has been developed for preparing porous hexadecyltrimethylammonium-coated Pt-Ag nanosponges using ascorbic acid. As determined via electron diffraction and mapping element measurements, the nanosponges feature fcc and mixed-alloy structures. The nanosponges were successfully deposited on the sidewalls of sodium dodecyl sulfate-micelle-functionalized herringbone graphite nanofibers (Pt-Ag/GN) using an electrostatic attraction. Further, as supported by in situ analyses, the mass activity and electrochemical kinetics of the Pt-Ag/GN nanocomposite toward the electrocatalysis of the oxygen reduction reaction (ORR) were studied. The results demonstrate that the mass activity of Pt-Ag/GN is 5.59 × 10⁻³ mA μg_pt⁻¹ and greater than 3.91 × 10⁻³ mA μg_pt⁻¹, the commercial Pt/C (at −0.15 V vs. Ag/AgCl). The numbers of ORR transfer electrons on the new composites reached 3.44 (at −0.15 V vs. Ag/AgCl), which shows that the ORR occurred quickly.     

Advanced Pd-based nanomaterials for electro-catalytic oxygen reduction in fuel cells: A review

Devising cost-effective and high-performance nanocatalysts for the inherently slow oxygen reduction reaction (ORR) represents a critical hurdle in the commercial improvement of fuel cells for energy conversion. Recently, considerable attempts have concentrated on exploring Pd-based nanocatalysts with advanced stability to utilize as substitutes for Pt. In this review, we first describe ORR mechanisms and summarize research conducted with Pd electro-catalysts, including single and alloyed Pd nanostructures on different substrates. The application of Pd catalysts as cathode nanomaterials in proton exchange membrane fuel cells (PEMFCs), direct methanol fuel cells (DMFCs), and anion exchange membrane fuel cells (AEMFCs) is also reviewed. The insights into the connections between catalytic performance, structure, and preparation process are addressed. In particular, approaches for fabricating efficient Pd electro-catalysts, such as increasing the number of reactive centers and modifying nanoparticle-support interactions, are discussed. Challenges and prospects for upcoming investigations in developing desirable ORR nanocatalysts are highlighted.     

In-situ facile synthesis of heterostructural Co||MnCo2O4.5/NC with active oxygen vacancies and its bifunctional electrocatalysis for oxygen reduction and oxygen evolution reaction

A potential non-noble metal oxide catalyst with its low-cost and efficient catalytic ability attract increasing attention. In this paper, a highly efficient bifunctional electrocatalyst Co||MnCo₂O_4.5/NC with heterostructure and oxygen vacancies is prepared utilizing solid reaction in-situ. The optimal catalyst is obtained at 650 °C with the mass ratio (1:8) of MnCo₂O_4.5 and Dicyandiamide (DCD). It shows excellent electrocatalytic activity for oxygen reduction reaction (ORR) with high half-wave potential (0.81 V) and limit current density (6.22 mA cm^?2), which is better than that of the commercial 20% Pt/C(0.81 V, 5.52 mA cm^?2). At the same time, it also exhibits superior electrocatalytic activity for oxygen evolution reaction (OER) with low overpotential (330 mV) and a faster dynamics process. The superior electrocatalytic properties may be resulted from the presence of heterostructure and increasing ratio of oxygen vacancies, which helps to the rapid transfer of electrons and creates more active sites. Moreover, the self-generated N-doped carbon provides high conductivity of the as-prepared Co||MnCo₂O_4.5/NC composite. It can be seen that the application of interface engineering technologies is useful for improving the performance of the catalyst, providing an effective and facile synthesis strategy for non-noble metal catalyst.     

Recent innovations of silk-derived electrocatalysts for hydrogen evolution reaction,oxygen evolution reaction and oxygen reduction reaction

Numerous researches have proved that heteroatom-doping, especially N-doping, is able to enhance the electrocatalytic performance for carbon materials toward water electrolysis and oxygen reduction reaction. Hence, the production of N-doped carbon materials from cheap and earth-abundant precursor resources such as biomass materials has great potential in the application of these fields. Among various biomass precursors, silk, a N-rich protein, is an ideal candidate for the synthesis of N-doped carbon. Meanwhile, without addition of chemical N-rich precursors during preparation, N-doped carbon derived from silk is clean and easy to synthesize but possesses superb performance. Silk derived catalysts can exhibit overpotential of 61 mV @ 10 mA/cm² (49 mV @ 10 mA/cm² of commercial 20%Pt/C for comparison) and Tafel slope of 89 mV/dec towards hydrogen evolution reaction. To date, great progress has been made in the application of silk-derived catalysts to electrocatalysts, but there exists few summary work. Herein, we summarized recent progress on silk-derived electrocatalysts, focusing on their preparation process and their application on water electrolysis and oxygen reduction reactions. This review provides consolidated accounts of silk-derived catalysts and highlights ideas of their preparation and their performance.     

Development of ruthenium-based bimetallic electrocatalysts for oxygen reduction reaction

Ruthenium-based bimetallic electrocatalysts with non-noble metals such as Ti, Cr, Fe, Co and Pb were synthesized on a porous carbon support using a chelation process. Rotating ring disk electrode measurements indicated that RuFeN_x/C showed the catalytic activity and selectivity toward the four-electron reduction of oxygen to water comparable to those of the conventional Pt/C catalysts. The performance of the membrane-electrode assembly prepared with the RuFeN_x/C cathode catalyst was evaluated for 150 h of continuous operation.