通过铁掺杂和造孔提高氮掺杂石墨烯/碳纳米管复合物电催化氧还原性能的研究（英文）

氧还原反应催化剂的性能直接影响着能源转换和存储器件如燃料电池和金属-空气电池的性能. 开发低成本、高性能的非铂族金属氧还原催化剂对于这类器件的实际应用和商业化十分重要,因此备受关注. 氮掺杂的石墨烯/碳纳米管复合物同时具备碳纳米管的良好导电性能和有利于传质的三维网络结构优点,以及氮掺杂石墨烯的高活性优点,因此有望发展为这类可替代铂族催化剂的氧还原电催化剂之一,但目前其催化性能还需进一步提高. 本文研究发现通过在氮掺杂石墨烯/碳纳米管复合物的过程中引入铁元素可以有效提高催化剂的氧还原活性,并且发现通过在热处理和氮掺杂过程中加入二氧化硅纳米颗粒及随后除去二氧化硅,可以在氮掺杂的石墨烯/碳纳米管复合物材料中有效地形成多孔结构. 这种多孔结构的形成不仅可以在复合物中引入更多的高活性催化位点,而且有利于暴露更多的催化活性位并促进氧还原反应中的传质过程. 结合碳纳米管、石墨烯和多孔结构的三者优点,所制备的多孔氮掺杂碳材料表现出优异的电催化氧还原性能. 进一步的实验表明,这类材料还表现出优异的抗甲醇中毒能力和良好的稳定性,因此在性能改进后有望用于燃料电池等能量转换与存储器件.     

模板辅助合成氮掺杂的多孔碳基氧还原电催化剂的研究进展（英文）

氮掺杂的多孔碳材料有望能取代当前普遍应用于质子交换膜燃料电池和金属-空气电池阴极中的贵金属氧还原催化剂,因而备受关注.模板辅助合成技术作为一种可靠、通用的方法已经在多孔碳电催化剂的制备中得到了广泛的应用.在碳基ORR电催化剂中,其ORR活性受到诸多因素的影响,如掺杂剂的浓度及其在碳上的分子掺杂态、孔洞结构、比表面积以及碳基材料的导电性等.本文对近期氮掺杂多孔碳电催化剂的设计、制备、功能化及其在氧还原电催化中的应用研究进展进行了总结,同时展望了模板辅助合成法的一些发展趋势.     

模板辅助合成氮掺杂的多孔碳基氧还原电催化剂的研究进展

氮掺杂的多孔碳材料有望能取代当前普遍应用于质子交换膜燃料电池和金属-空气电池阴极中的贵金属氧还原催化剂,因而备受关注. 模板辅助合成技术作为一种可靠、通用的方法已经在多孔碳电催化剂的制备中得到了广泛的应用. 在碳基ORR电催化剂中,其ORR活性受到诸多因素的影响,如掺杂剂的浓度及其在碳上的分子掺杂态、孔洞结构、比表面积以及碳基材料的导电性等. 本文对近期氮掺杂多孔碳电催化剂的设计、制备、功能化及其在氧还原电催化中的应用研究进展进行了总结,同时展望了模板辅助合成法的一些发展趋势.     

石墨烯基氧还原催化剂在金属空气电池中的应用

随着金属空气电池技术的不断发展,氧还原催化剂成为限制其动力化的最主要瓶颈之一。近几年来,石墨烯基氧还原催化剂(GORRC)由于优异的氧还原催化活性而备受关注。本文结合石墨烯基氧还原催化剂的研究现状,将其分为三类:石墨烯作氧还原催化剂载体,氮掺杂石墨烯作为氧还原催化剂,以及氮掺杂石墨烯与其他催化剂形成的复合催化体系,并对这三种石墨烯基氧还原催化剂进行了详细的综述。石墨烯作为一种优良的催化剂载体,能够显著降低活性物质负载量,提高氧还原催化剂的催化活性和长期稳定性。氮掺杂石墨烯显示了优良的氧还原催化性能。氮掺杂石墨烯与其他催化剂复合后,由于两者之间的相互作用,可得到性能更为优异的氧还原催化剂。最后,本文还对石墨烯基氧还原催化剂及其在金属空气电池中的研究前景和发展方向进行了展望,指出了将来的研究重点。     

碳基无金属氧还原电催化剂研究的新进展

以替代铂为目标的高性能廉价氧还原电催化剂的研究为当今科学前沿. 近年来人们发现, 掺杂的碳基纳米结构具有催化活性高、稳定性好、资源丰富、抗CO和抗甲醇能力强等优点, 是一种新型无金属氧还原电催化剂, 具有替代铂基催化剂的潜力. 本文结合作者课题组的最新研究成果, 简要综述了碳基无金属氧还原电催化剂研究的主要进展, 重点关注了富电子氮和缺电子硼单/共掺杂的碳纳米结构的氧还原催化性能及其与电子结构的关系, 展望了碳基无金属氧还原催化剂的发展策略与前景.     

单源MOF衍生具有三维有序大孔结构的氮掺杂碳包覆铁-氮合金复合材料用于高效氧还原

氧还原反应在一些能源转换系统如金属-空气电池中起着至关重要的作用.目前贵金属基材料(Pt/C)被认为是最有效的氧还原电催化剂,然而价格昂贵和储量有限等因素限制了它的商业化应用,因此探索高效的非贵金属氧还原电催化剂具有重要的意义.近年来,负载过渡金属铁的多孔碳催化剂由于独特的结构和优异的氧还原催化活性成为替代铂基催化剂最有潜力的候选者.该类材料的合成通常采用直接煅烧含有氮源、碳源和铁盐的混合前驱体的制备方法,但是热解时材料的多孔结构以及活性位点的均匀分布很难得到有效的控制.近年来,金属有机框架(MOFs)由于其多孔结构和组成可控等优点而经常被用作自牺牲模板来制备负载铁基纳米材料的多孔碳催化剂,并表现出优异的电催化活性.目前以MOF为前驱体制备高活性的载铁氮掺杂碳复合材料通常需要引入额外的氮源或铁源,因此选择氮含量丰富的铁基MOF材料作为单源前驱体制备载铁氮掺杂多孔碳复合材料具有重要的意义.除此之外,具有多级孔隙率的催化剂可以改善反应时的传质过程,同时有序交联的网络结构能够提供连续的电子传输.本文报道了一种简单可控的制备具有三维有序大孔结构的载铁氮掺杂多孔碳复合催化剂的合成方法,该材料表现出优异的电催化氧气还原性能和优异的催化稳定性.首先,以氮含量丰富的双氰胺和吡嗪配体所构筑的Fe-MOF作为前驱体,利用具有均一尺寸的聚苯乙烯微球作为造孔剂,合成得到了具有三维有序大孔结构的Fe-MOF前驱体,然后通过高温煅烧该单源前驱体制备得到具有三维有序大孔结构的氮掺杂多孔碳包覆铁-氮合金的复合型催化剂(3DOM Fe/Fe-NA@NC).扫描电镜和透射电镜结果表明,材料内形成了有序交联的大孔结构;氮气吸附测试表明,刻蚀之后材料的比表面积明显增加,结合分级多孔特性可以共同促进催化反应的传质过程.粉末X射线衍射结果证实了多孔碳材料中铁和铁-氮合金物种的成功合成.电化学测试结果表明,在0.1 M KOH电解液中,3DOM Fe/Fe-NA@NC-800催化剂表现出优于Pt/C的氧还原活性,其半波电位(E_1/2)为0.88 V,大于商业Pt/C的半波电位(E_1/2=0.85 V).同时,3DOM Fe/Fe-NA@NC-800表现出更加优异的稳定性,经过20000 s测试后,其电流保持率为94%,而Pt/C只保持了78%.关于活性位点探究的对比实验证明在所制备的复合材料中,铁物种作为高效的活性位点参与了电催化氧还原反应,与氮掺杂多孔碳之间的协同作用共同主导了3DOM Fe/Fe-NA@NC优异的氧还原活性.得益于其优异的氧还原活性,将其作为阴极活性材料组装为锌-空气电池进一步探究了其在实际应用中的可行性.本结果拓宽了高效的铁基催化剂的类型,同时也为制备封装非贵金属的多孔碳基催化剂提供了实验指导和理论依据.     

Ya‐Ru Lv,Xue‐Jing Zhai,Shan Wang,Hong Xu,Rui Wang #, Shuang‐Quan Zang

氧还原反应在一些能源转换系统如金属-空气电池中起着至关重要的作用.目前贵金属基材料(Pt/C)被认为是最有效的氧还原电催化剂,然而价格昂贵和储量有限等因素限制了它的商业化应用,因此探索高效的非贵金属氧还原电催化剂具有重要的意义.近年来,负载过渡金属铁的多孔碳催化剂由于独特的结构和优异的氧还原催化活性成为替代铂基催化剂最有潜力的候选者.该类材料的合成通常采用直接煅烧含有氮源、碳源和铁盐的混合前驱体的制备方法,但是热解时材料的多孔结构以及活性位点的均匀分布很难得到有效的控制.近年来,金属有机框架(MOFs)由于其多孔结构和组成可控等优点而经常被用作自牺牲模板来制备负载铁基纳米材料的多孔碳催化剂,并表现出优异的电催化活性.目前以MOF为前驱体制备高活性的载铁氮掺杂碳复合材料通常需要引入额外的氮源或铁源,因此选择氮含量丰富的铁基MOF材料作为单源前驱体制备载铁氮掺杂多孔碳复合材料具有重要的意义.除此之外,具有多级孔隙率的催化剂可以改善反应时的传质过程,同时有序交联的网络结构能够提供连续的电子传输.本文报道了一种简单可控的制备具有三维有序大孔结构的载铁氮掺杂多孔碳复合催化剂的合成方法,该材料表现出优异的电催化氧气还原性能和优异的催化稳定性.首先,以氮含量丰富的双氰胺和吡嗪配体所构筑的Fe-MOF作为前驱体,利用具有均一尺寸的聚苯乙烯微球作为造孔剂,合成得到了具有三维有序大孔结构的Fe-MOF前驱体,然后通过高温煅烧该单源前驱体制备得到具有三维有序大孔结构的氮掺杂多孔碳包覆铁-氮合金的复合型催化剂(3DOM Fe/Fe-NA@NC).扫描电镜和透射电镜结果表明,材料内形成了有序交联的大孔结构;氮气吸附测试表明,刻蚀之后材料的比表面积明显增加,结合分级多孔特性可以共同促进催化反应的传质过程.粉末X射线衍射结果证实了多孔碳材料中铁和铁-氮合金物种的成功合成.电化学测试结果表明,在0.1 MKOH电解液中, 3DOMFe/Fe-NA@NC-800催化剂表现出优于Pt/C的氧还原活性,其半波电位(E1/2)为0.88 V,大于商业Pt/C的半波电位(E1/2=0.85 V).同时, 3DOM Fe/Fe-NA@NC-800表现出更加优异的稳定性,经过20000 s测试后,其电流保持率为94%,而Pt/C只保持了78%.关于活性位点探究的对比实验证明在所制备的复合材料中,铁物种作为高效的活性位点参与了电催化氧还原反应,与氮掺杂多孔碳之间的协同作用共同主导了3DOM Fe/Fe-NA@NC优异的氧还原活性.得益于其优异的氧还原活性,将其作为阴极活性材料组装为锌-空气电池进一步探究了其在实际应用中的可行性.本结果拓宽了高效的铁基催化剂的类型,同时也为制备封装非贵金属的多孔碳基催化剂提供了实验指导和理论依据.     

ZIF-67衍生的Ag/Co@NC材料及其氧还原性能的研究

氮掺杂的多孔碳材料可作为氧还原反应的催化剂,本文借助ZIF-67富氮多孔的特殊结构,采用湿式逐步还原法将Ag嵌入ZIF-67孔腔内,然后在Ar中碳化成功地制备了Ag/Co双金属嵌入的氮掺杂的多孔碳复合材料（Ag/Co@NC）作为氧还原反应的催化剂. 为了证明Ag的突出作用,同时在Ar中碳化了ZIF-67制备了Co嵌入的氮掺杂的多孔碳材料（Co@NC）. 利用扫描电子显微镜、透射电子显微镜、X射线衍射、X射线光电子能谱以及比表面积分析对材料的显微形貌、物相组成、结构进行分析,采用循环伏安和线性扫描极化曲线对材料的氧还原催化活性和催化稳定性进行研究. 结果表明,Ag的嵌入未改变ZIF-67的晶体结构,但是大大提高了材料的氧还原催化活性. Ag/Co@NC材料的半波电位和起始电位均高于Co@NC材料,且其在1000次循环伏安测试前后的半波电位变化仅为30 mV,显示出很好的催化稳定性和甲醇耐受性,可作为燃料电池和金属-空气电池的阴极催化剂.     

ZIF-67衍生的Ag/Co@NC材料及其氧还原性能的研究（英文）

氮掺杂的多孔碳材料可作为氧还原反应的催化剂,本文借助ZIF-67富氮多孔的特殊结构,采用湿式逐步还原法将Ag嵌入ZIF-67孔腔内,然后在Ar中碳化成功地制备了Ag/Co双金属嵌入的氮掺杂的多孔碳复合材料(Ag/Co@NC)作为氧还原反应的催化剂.为了证明Ag的突出作用,同时在Ar中碳化了ZIF-67制备了Co嵌入的氮掺杂的多孔碳材料(Co@NC).利用扫描电子显微镜、透射电子显微镜、X射线衍射、X射线光电子能谱以及比表面积分析对材料的显微形貌、物相组成、结构进行分析,采用循环伏安和线性扫描极化曲线对材料的氧还原催化活性和催化稳定性进行研究.结果表明,Ag的嵌入未改变ZIF-67的晶体结构,但是大大提高了材料的氧还原催化活性. Ag/Co@NC材料的半波电位和起始电位均高于Co@NC材料,且其在1000次循环伏安测试前后的半波电位变化仅为30 mV,显示出很好的催化稳定性和甲醇耐受性,可作为燃料电池和金属-空气电池的阴极催化剂.     

利用MOF-253衍生氮掺杂碳限域效应促进Pt纳米单晶电催化剂的氧析出反应

目前,为了有效解决电化学能量转化反应动力学过程缓慢和商业化应用等问题,需要大力提高催化剂的电催化活性和稳定性,并大幅降低贵金属催化剂的用量.通常,铂(Pt)基催化剂对燃料电池的氧还原反应(ORR)和水电解过程的氢析出反应(HER)表现出很高的活性.然而,对于高效的金属-空气电池和水电解装置,其中的氧析出反应(OER)则需要高活性的非Pt电催化剂来降低电化学过电位及提高其对高电位的耐受性.虽然相较于Pt催化剂,IrO2和RuO2等贵金属催化剂表现出了更高的OER活性,然而,它们的稳定性差,难以满足实际应用需求,严重阻碍了其在金属-空气电池和水电解中的应用.通常,Pt对OER的低效催化主要归因于在OER电催化过程中Pt与电解液直接接触,导致Pt表面快速被氧化,形成Pt氧化物(Pt^+4O2和Pt^+2O)层.形成的Pt氧化物对OER不起催化作用,从而降低了Pt的利用率和总的水电解效率.为了避免Pt表面的快速氧化,实现高的OER性能,我们将Pt金属纳米粒子有效地限域在超薄功能多孔碳层内.前期,已有大量的有关金属基ORR和HER催化剂研究证明,这种策略对于稳定金属纳米颗粒非常有效,可有效避免金属催化剂的快速氧化,而且还可抑制金属颗粒迁移和团聚;此外,还有利于增强催化剂的导电性和离子物种的扩散能力,从而提高催化剂的电催化性能.然而,要达到提高金属催化剂OER电催化性能的目的,还需要设计一种具有优良结构的功能化异质原子掺杂多孔碳基限域材料.金属有机框架(MOF),特别是MOF-253,由于具有较高的柔韧性、丰富的孔、可控的几何结构和高比表面积,被认为是制备功能多孔碳基限域材料的理想前驱体.为此,通过结合功能多孔碳基材料的限域作用及MOF-253和超细Pt纳米单晶的优势,本文合成了MOF-253衍生氮掺杂碳(N/C)限域的Pt纳米单晶(Pt@N/C)核壳型电催化剂.制备的Pt-N-C框架不仅具有超薄的氮掺杂活性多孔碳保护层壳体(平均厚度为0.51 nm),还有具高度分散和稳定化的Pt纳米单晶核体;值得指出的是,因受到碳层的限域作用,即使经900℃的高温处理,Pt纳米单晶仍保持了较小的晶体尺寸(平均粒径仅为6.7 nm);此外,该催化剂的Pt载量较低,仅为6.1wt%(Pt@N/C-10).将其作为OER电催化剂,表现出优异的OER性能:在10 mA cm^-2电流密度下,其过电位仅为298 mV,低于商业IrO2催化剂(353 mV);而且,经2000周加速电位扫描后,其电位仅降低19.4 mV,也低于IrO2(23.3 mV).本文很好地证明了通过构建空间限域结构可以有效解决Pt等金属催化剂因表面氧化而导致OER动力学活性和稳定性低的问题.     

Caging Porous Co-N-C Nanocomposites in 3D Graphene as Active and Aggregation-Resistant electrocatalyst for Oxygen Reduction Reaction北大核心CSCD

Oxygen reduction reaction (ORR) is the cornerstone reaction of many renewable energy technologies such as fuel cells and rechargeable metal-air batteries.The Pt-based electrocatalysts exhibit the highest activity toward ORR, but their large implementation is greatly prohibiting by unaffordable cost and inferior durability.During electrode manufacturing and electrochemical reaction, severe aggregation of catalyst nanoparticles induced by size effect further limits the operational performance of electrocatalysts.We report a new strategy for fabrication of active and aggregation-resistant ORR electrocatalyst by caging metal-organic frameworks derived Co-N-C nanocomposites in permeable and porous 3D graphene cages via sprayed drying the mixed colloids of ZIF-67 nanoparticles and graphene oxide, followed by annealing.The 3D graphene cages around Co-N-C nanocomposites not only provide a continuous conductive network for charge transfer, but also prevent the active phase from aggregation during electrode manufacturing and electrochemical reactions.When evaluated as an ORR electrocatalyst, the material exhibited comparable activity but superior stability to commercial Pt/C catalyst in an alkaline electrolyte. © 2018 Chinese Chemical Society. All rights reserved.     

Preparation and electrochemical performances of silver (alloy) nanoparticles decorated on reduced graphene oxide,using self-polymerization of dopamine in an acidic environment

Self-polymerization of dopamine, in either an alkaline or an acidic environment, to form polydopamine is a material-independent surface coating technique, influencing almost all areas of material science and engineering. We demonstrated a simple, two-step method to prepare in-situ silver or silver-copper alloy nanoparticles on the surface of reduced graphene oxides, using polydopamine formed in an acidic medium. The acidic medium was created by a nonthermal micro-hollow cathode discharge device and the device was operated at atmospheric pressure, using air as the working gas. The nanocomposites were characterized with SEM, EDX, ICP-OES, and FT-IR; the electrochemical catalytic activity was tested using rotating disk electrode. The characterization methods confirmed the formation of the nanocomposites, which contain polydopamine, reduced graphene oxides, and metal nanoparticles or nanoalloy. We hypothesized that by alloying silver and copper on the surface of reduced graphene oxides, the oxygen reduction reaction (ORR) catalytic activity of the nanocomposites will be enhanced through both alloying and substrate effects. The size range of the nanoparticles is between 10 nm and 15 nm. We find that both the silver and alloy samples catalyze the ORR via a four-electron mechanism. The alloy nanocomposites showed better performance indicator parameters than the silver one, in both mass activity and kinetic current density. This preparation method has paved a new way of synthesizing an ORR catalyst in an environmentally friendly manner.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-hydroxy-imidamide-functionalized graphene: an efficient metal-free electrocatalyst for oxygen reduction

Metal-free electrocatalysts for oxygen reduction reaction (ORR) are key to the development of efficient, durable, and low-cost alternatives to noble-metal-based electrocatalysts in fuel cell cathodes. In recent years, many efforts are directed to the metal-free catalyst based on heteroatom-doped graphene. In this work, we demonstrate that the graphene surface can be converted into the catalyst for the oxygen reduction by chemical functionalization. In this context, we first synthesized malononitrile-functionalized graphene oxide. Amidoximation of nitrile group and reduction in graphene oxide were then carried out by hydroxylamine in one step. The electrochemical behavior of functionalized graphene-modified electrode for the reduction in oxygen was studied. The results showed that the electrocatalyst fabricated by this method exhibited striking catalytic activities in alkaline solution. In alkaline solution, this catalyst showed a competitive activity to the commercial Pt catalyst via four-electron transfer pathway with better ORR selectivity and stability. In addition, this metal-free electrocatalyst exhibited tolerance to methanol crossover effect. Based on its outstanding performance, this functionalized graphene electrocatalyst showed the promising prospect of a metal-free catalyst for fuel cell with much lower cost than currently used Pt/C catalyst.     

In-Situ Electrodeposition of Rhodium nanoparticles Anchored on Reduced Graphene Oxide nanosheets as an Efficient Oxygen Reduction Electrocatalyst

A simple, versatile, and cost-effective one-pot electrochemical deposition is used to fabricate rhodium (Rh) nanoparticles decorated surface of reduced graphene oxide (rGO) functionalized glassy carbon electrode (GCE) for oxygen reduction reaction (ORR) in alkaline media. The chemical and physical structure of the sample is probed via transmission electron microscopy, rotating disk electrode (RDE), X-ray photoelectron spectroscopy, linear sweep voltammetry, and Raman spectroscopy. The synergistic effects between the unique properties of Rh nanoparticles and rGO creates such innovative hybrid that exhibits a catalytic activity comparable to that of the commercial platinum electrocatalyst (Pt/C). As a result, the as-electrodeposited Rh@rGO hybrid exhibits outstanding ORR activity in alkaline media, as evidenced by a larger diffusion-limited current, greater positive onset potential, much better stability and methanol tolerance than Pt/C under the same conditions.     

Perfluorosulfonic acid-functionalized Pt/graphene as a high-performance oxygen reduction reaction catalyst for proton exchange membrane fuel cells

Platinum nanoparticles (Pt NPs) on carbon black (CB) have been used as catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells for a while. However, this catalyst has suffered from aggregation and dissolution of Pt NPs as well as CB dissolution. In this study, we resolve those issues by developing perfluorosulfonic acid (PFSA)-functionalized Pt/graphene as a high-performance ORR catalyst. The noncovalently bonded PFSA remarkably decreases the dissolution and aggregation of Pt NPs. Moreover, unlike typical NP functionalization with other capping agents, PFSA is a proton conductor and thus efficiently develops a triple-phase boundary. These advantageous features are reflected in the improved cell performance in electrochemical active surface area, catalytic activity, and long-term durability, compared to those of the commercial Pt/C catalysts and graphene-based catalysts with no such treatment.     

Cobalt and nitrogen codoped porous carbon as superior bifunctional electrocatalyst for oxygen reduction and hydrogen evolution reaction in alkaline medium

Metal (cobalt)/nitrogen codoped carbon was first fabricated by pyrolysis of coordinated “noncarbonizable” polymer as bifunctional catalyst for ORR and HER, which showed better electrocatalytic performances than most bifunctional doped carbon catalysts in alkaline electrolyte.     

Co3O4/聚吡咯/石墨烯碱性溶液中电化学还原氧

燃料电池具有较高的能量密度和发电效率,以清洁能源为原料,零污染排放,是一种具有发展前景的能量储存和转化装置.阴极氧还原反应(ORR)在燃料电池中起着关键作用.ORR广泛采用贵金属铂基催化剂,但是它们价格昂贵,电子动力学转移速率慢,碱性条件下易团聚,这些亟需解决的问题阻碍了燃料电池商业化进程.近期,一些非贵金属催化剂被广泛研究,例如氮掺杂碳材料、Fe/N/C和Co/N/C材料等,它们有可能在未来替代铂基催化剂.我们的目标是合成新型高催化活性的Co/N/C及其衍生非贵金属材料,用于ORR催化反应.由于石墨烯具有独特的形貌、较大的比表面积和良好的导电性,其表面含有功能化的官能团,所以我们选择石墨烯作为碳载体.首先,用改性休克尔方法合成了氧化石墨烯(GO),为了提高其催化活性,采用聚吡咯作为氮源对其进行了氮掺杂,制备了聚吡咯/氧化石墨烯(Ppy/GO).通过ORR催化性能测试发现,GO对ORR具有一定的催化活性,它的起始电位和阴极电流电位分别为–0.31 V vs SCE和–0.38 V vs SCE;Ppy/GO的起始电位和阴极电流电位分别为–0.20 V vs SCE和–0.38 V vs SCE,氮掺杂对GO的催化活性有所提高.采用水热法沉积氧化钴合成了Co3O4/聚吡咯/氧化石墨烯(Co3O4/Ppy/GO).其形貌为Co3O4分散在氮掺杂GO表面.在KOH电解质(0.1 mol/L)中测试,Co3O4/Ppy/GO的起始电位和阴极电流电位分别为–0.20 V和–0.38 V vs SCE.经过800℃高温煅烧处理后,Co3O4/Ppy/GO-800的催化活性明显提高,起始电位和阴极电流电位分别达到–0.10 V和–0.18 V vs SCE.ORR电子转移数为3.4,接近于4电子反应途径.Co3O4/Ppy/GO对ORR的催化活性及4电子催化选择性较高,可能是由于纳米形态的Co3O4和Ppy/GO之间具有较强的表面作用力,聚吡咯掺杂的氧化石墨烯具有较强的电子储存及释放能力.综上,我们通过水热法制备了钴、氮共掺杂的GO,并研究了其对ORR的催化活性和电子转移选择性.结果表明Co3O4/Ppy/GO是一种高效的非贵金属电催化剂,在碱性电解质中具有很高的ORR催化活性,在燃料电池阴极催化剂方面很有前景.     

铁氮掺杂对石墨烯担载铂催化剂氧还原反应活性的影响

高氧还原活性担载铂催化剂的研发是加快质子交换膜燃料电池商业化进程的主要手段之一。以石墨烯为碳源,1,10-菲啰啉为氮源,FeCl3为铁源,用浸渍法制备铁氮掺杂石墨烯(Fe/N-G)载体,并通过乙二醇还原法获得PtFe/N-G催化剂,探究铁氮原子的引入对石墨烯担载铂催化剂氧还原反应催化活性的影响。采用X射线衍射、比表面积和孔径分布测试、X射线光电子能谱等表征手段对载体及催化剂结构进行表征,使用电化学方法对载体和催化剂的氧还原反应活性进行测试。结果表明,PtFe/N-G催化剂的氧还原反应起始电位及半波电位分别为0.96 V、0.83 V,优于相同Pt担载量的商业20%Pt/C催化剂。铁氮掺杂后,石墨烯载体具有较大的孔径更有利于氧还原反应过程中生成物与反应物的传递,PtFe/N-G催化剂中存在吡啶氮和Fe-N型氮与铂纳米颗粒的协同催化,以及铂纳米颗粒与铁氮掺杂石墨烯载体间的相互作用,是PtFe/N-G催化剂具有优异的氧还原催化活性的可能原因。     

Nitrogen,Phosphorus, and Fluorine Tri‐doped Graphene as a Multifunctional Catalyst for Self‐Powered Electrochemical Water Splitting

Electrocatalysts are required for clean energy technologies (for example, water‐splitting and metal‐air batteries). The development of a multifunctional electrocatalyst composed of nitrogen, phosphorus, and fluorine tri‐doped graphene is reported, which was obtained by thermal activation of a mixture of polyaniline‐coated graphene oxide and ammonium hexafluorophosphate (AHF). It was found that thermal decomposition of AHF provides nitrogen, phosphorus, and fluorine sources for tri‐doping with N, P, and F, and simultaneously facilitates template‐free formation of porous structures as a result of thermal gas evolution. The resultant N, P, and F tri‐doped graphene exhibited excellent electrocatalytic activities for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The trifunctional metal‐free catalyst was further used as an OER–HER bifunctional catalyst for oxygen and hydrogen gas production in an electrochemical water‐splitting unit, which was powered by an integrated Zn–air battery based on an air electrode made from the same electrocatalyst for ORR. The integrated unit, fabricated from the newly developed N, P, and F tri‐doped graphene multifunctional metal‐free catalyst, can operate in ambient air with a high gas production rate of 0.496 and 0.254 μL s⁻¹ for hydrogen and oxygen gas, respectively, showing great potential for practical applications.     

Nitrogen,Phosphorus, and Fluorine Tri‐doped Graphene as a Multifunctional Catalyst for Self‐Powered Electrochemical Water Splitting

Electrocatalysts are required for clean energy technologies (for example, water‐splitting and metal‐air batteries). The development of a multifunctional electrocatalyst composed of nitrogen, phosphorus, and fluorine tri‐doped graphene is reported, which was obtained by thermal activation of a mixture of polyaniline‐coated graphene oxide and ammonium hexafluorophosphate (AHF). It was found that thermal decomposition of AHF provides nitrogen, phosphorus, and fluorine sources for tri‐doping with N, P, and F, and simultaneously facilitates template‐free formation of porous structures as a result of thermal gas evolution. The resultant N, P, and F tri‐doped graphene exhibited excellent electrocatalytic activities for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The trifunctional metal‐free catalyst was further used as an OER–HER bifunctional catalyst for oxygen and hydrogen gas production in an electrochemical water‐splitting unit, which was powered by an integrated Zn–air battery based on an air electrode made from the same electrocatalyst for ORR. The integrated unit, fabricated from the newly developed N, P, and F tri‐doped graphene multifunctional metal‐free catalyst, can operate in ambient air with a high gas production rate of 0.496 and 0.254 μL s^?1 for hydrogen and oxygen gas, respectively, showing great potential for practical applications.