铁氮共掺杂介孔碳材料的简易制备及其氧还原反应催化性能

氧还原反应(ORR)是燃料电池阴极重要的电化学反应过程,其自发反应进程缓慢,对氧还原反应起高效催化作用的催化剂面临价格昂贵、合成流程复杂、污染环境等问题,因此探索合成简单、环境友好的氧还原催化剂制备方法具有重要意义。铁氮共掺杂介孔碳材料(Fe-N/MC)是一种有巨大应用价值的非贵金属氧还原反应催化剂。本工作通过在马弗炉中的半封闭体系内高温碳化小分子前驱体得到介孔碳材料(MC_M),再把获得的MC_M与铁盐混合在管式炉中高温处理制备得到铁氮共掺杂介孔碳材料(Fe-N/MC_MT)。该方法热解条件简单,无需模板剂和NH₃、HF等有毒物质。由于MC_M含有较高的氮和氧元素,有利于提升介孔碳材料表面的亲水性和配位能力,通过MC_M和铁盐制备出的Fe-N/MC_MT含有丰富的、催化ORR的Fe-N_x活性位点,其起始电位和半波电位分别为0.941和0.831 V(vs RHE),比商业化Pt/C催化剂的起始电位和半波电位分别正34和16...     

氮硫共掺杂碳材料均匀担载核壳纳米颗粒Co@Co9S8作为氧还原催化剂的研究

开发高效、稳定的非贵金属氧还原(ORR)催化剂是促进燃料电池商业化进程的关键。通过树脂衍生N、S共掺杂碳材料负载原位生成的Co@Co₉S₈核壳结构纳米颗粒，制备出一种具有良好活性和稳定的非贵金属催化剂Co@Co₉S₈/NSC。电化学测试结果表明：Co@Co₉S₈/NSC催化剂的半波电位(E_1/2)和极限电流密度可与商业Pt/C催化剂相媲美。同时相较商业Pt/C催化剂，其还具有极好的抗甲醇活性。此外，计时电流测试表明：持续老化10000s后，Co@Co₉S₈/NSC的电流密度保持了初始值的97.5%,远低于商业Pt/C催化剂的23.3%。为构建高活性高稳定性核壳结构ORR催化剂提供了新的思路，同时其思路也可以应用于其他新能源电极材料如Li-空气电池、Li-S电池及超级电容器等。     

Co修饰的碳载Pt纳米粒子催化剂的制备与表征

质子交换膜燃料电池阴极需要使用高活性的电催化剂来加速氧还原反应(ORR)速率,而提高活性成分贵金属铂(Pt)的功能反应利用率可解决其关键问题.本工作利用过渡金属钴Co(Ⅱ)?有机框架(Co?MOF)为前驱体合成ORR催化剂载体Co/C,并采取浸渍?液相还原法负载Pt纳米粒子制备了合金Pt?Co/C催化剂.通过对样品的孔隙结构、物相结构、微观形貌等表征,证实了载体Co/C具有较大的比表面积和相互连通的分级介孔结构,其独特的形貌、丰富的孔隙结构使负载的Pt纳米颗粒均匀分布、粒径范围窄,平均粒径约为6.8 nm.进一步对催化剂进行电化学性能评价,其电化学活性表面积(ECSA)接近于商用Pt/C催化剂的值,结果表明合金催化剂中活性成分Pt具有较高的利用率,同时还表现出载体独特的孔隙结构优势.     

氢气还原法制备Pt/MoOx/C及其对氧还原的电催化性能

用氢气在高温下还原吸附到碳载体上的钼酸铵和氟铂酸,制备出Pt/MoOx/C金属-氧化物复合型催化剂.考察了Pt/MoOx/C催化剂的电化学性能,经旋转圆盘电极测试表明在低电位区Pt/MoOx/C对含甲醇溶液中的氧还原的催化活性高于Pt/C.     

酸处理对FeN/ZIF-8催化剂氧还原反应催化性能的影响

研发高性能、低成本的非贵金属阴极氧还原反应催化剂是目前质子交换膜燃料电池的主要研究方向之一。以1, 10-菲啰啉为氮源, FeSO₄·7H₂O为铁源, 考察以ZIF-8为载体制备的FeN/ZIF-8催化剂的氧还原反应催化性能, 并探究酸处理对FeN/ZIF-8催化剂结构及性能的影响。通过X射线衍射、比表面积和孔径分布测试、透射电子显微镜等物理表征手段对催化材料进行结构表征, 使用旋转圆盘电极对催化剂氧还原反应催化活性和稳定性进行测试。结果表明: 以ZIF-8为载体制备的催化剂含有Fe₃C, 以及具有较大的比表面积, 这可能是催化剂具有较高氧还原反应初始催化活性的原因。酸处理可去除催化剂中部分不稳定的含铁碳化物和无序碳结构, 使催化剂具有更大的比表面积、更丰富的介孔结构和更高的孔体积; 同时, 酸处理可提高碳基体的耐腐蚀性, 在老化测试中维持催化剂所具有的较高比表面积和丰富的介孔结构, 从而使FeN/ZIF-8-A催化剂表现出更好的氧还原反应活性和稳定性。     

基于金属-有机框架的M-N/C类催化剂在氧还原反应中的应用

燃料电池阴极发生氧还原反应(ORR)的动力学过程缓慢，通常需要Pt/C作为催化剂降低反应过电位。然而Pt作为一种贵金属，其使用将极大增加燃料电池的生产成本，因此开发非贵金属催化剂来替代Pt/C催化剂具有重要意义。金属有机框架材料(MOFs)因其具有高比表面积、有序多孔结构、拓扑结构可调等特点作为前驱体被广泛应用于M-N/C类催化剂的合成。M-N/C类催化剂继承了MOFs的结构特征，且具有丰富的活性位点，提高催化活性和分级结构以促进传质过程，因此表现出良好的ORR催化性能。从单金属/氮/碳和多金属/氮/碳组成角度出发，对近几年来关于M-N/C类催化剂的结构设计思路和合成策略进行了总结，阐述了其在ORR中的催化性能，展望了其未来发展前景。     

立方体咪唑骨架衍生CoFe合金纳米粒子嵌入N-掺杂石墨化碳中用于锌空气电池放电反应（英文）

目前,贵金属铂被认为是性能最优异的氧还原催化剂,但是其昂贵的价格、有限的储量制约了其大规模应用,因此制备具有高催化活性和稳定性的过渡金属基催化剂迫在眉睫.在本工作中,我们构筑了一种CoFe合金纳米颗粒嵌入到N-掺杂石墨化碳纳米结构中的复合材料(CoFe/NC)作为氧还原催化剂.我们首先制备了ZIF-67纳米立方体,再利用离子交换法在其骨架中引入Fe2+形成CoFe-ZIF前驱体.通过在惰性气氛下煅烧得到CoFe/NC催化剂.由于钴、铁及氮掺杂的协同作用,CoFe/NC-0.2-900催化剂(在900°C下煅烧掺杂0.2 mmol硫酸亚铁的CoFe/NC)表现出优异的氧还原性能,尤其是极限电流密度(6.4 mA cm^-2)远高于Pt/C(5.1 mA cm^-2).采用CoFe/NC-0.2-900和NiFeP/NF(负载在泡沫镍上的NiFeP)分别作为放电和充电反应催化剂组装的可充电锌空气电池,与传统的Pt/C+RuO2/C催化剂组装的电池相比,具有较低的充放电电压差、较大的功率密度和更优异的循环稳定性.     

碳纳米管锚定在中空碳上用于高效氧还原反应（英文）

设计和制备用于高效氧还原反应(ORR)的非贵金属基电催化剂对于清洁能源转换装置的开发至关重要,但又极具挑战性.在本工作中,我们通过热解双金属前驱体ZIF-Zn/Co,成功制备了一种新型的分级中空碳纳米复合材料HNCT-CNT.该材料富含Co-N_x位点以及原位形成的多壁碳纳米管.理论和实验表明, HNCT-CNT使ORR中间体的活化能垒降低,因而表现出了优异的ORR性能.最佳催化剂表现出较正的半波电位为0.85 V,极限电流密度高达6.36 mA cm^-2, Tafel斜率为58.2 mV dec^-1,且结构稳定性良好.此外,基于HNCT-CNT组装的锌空气电池还显示出1.49 V的开路电压和116.56 mW cm^-2的功率密度.综上,这种无机物模板法为制备金属有机框架化合物衍生的非贵金属基碳纳米电催化剂用于高效的电化学能源领域提供了一种新的方法.     

ZIFs材料对Fe/N/C催化剂氧还原性能的影响

过渡金属/氮/碳(M/N/C)催化剂是替代铂基催化剂用于氧还原反应(ORR)的理想材料。沸石咪唑骨架(ZIFs)材料结合了无机沸石的高稳定性和MOFs材料的高比表面积、高孔隙率及可调孔结构等特点,是制备M/N/C催化剂的优良前驱体。本工作以FeSO₄·7H₂O为铁源,1,10-菲啰啉为氮源,探究不同ZIFs材料对FeN/C-Z_x催化剂ORR性能的影响。通过X射线衍射、比表面积和孔径分布测试、透射电子显微镜等对催化剂进行结构表征,使用线性扫描伏安法对催化剂ORR催化活性进行测试。结果表明：FeN/C-Z₈催化剂表现出最佳的ORR活性,具有较小的Tafel斜率(64.98 mV/dec)且反应过程是近四电子过程;在经过25 000次循环后,FeN/C-Z₈催化剂的半波电位仅有20 mV的负移,表现出良好的稳定性。FeN/C-Z₈催化剂中存在的Fe₃C化合物可有效提高催化剂的催化性能;Zn²⁺在碳化过程中挥发使FeN/...     

碱性溶液中不同微观结构的Fe-N/C催化剂氧还原性能的稳定性对比研究

Fe-N/C催化剂在氧还原反应中的作用机理对于开发高效、可持续使用的非贵金属催化剂在聚合物电解质膜燃料电池中的应用至关重要, 但目前仍存在很多的难以攻克的问题。为了揭示纳米结构与电化学活性的关系, 本研究开发了一种具有高电化学活性的Fe-N/C氧还原催化剂, 该催化剂含有Fe-N_x位点和被氮掺杂的碳纳米管包裹的Fe/Fe₃C纳米晶体两种具有氧还原反应电化学活性的纳米结构。尽管不含贵金属铂, 本研究合成的Fe-N/C催化剂在碱性条件下仍显示出较高的ORR活性, 半波电势为0.86 V(vs RHE), 质量活性为18.84 A/g(0.77 V(vs RHE), 极限电流密度为-4.3 mA·cm ^-2。同时, 电子转移数为3.7(0.2 V(vs RHE), 说明Fe-N/C催化剂中4电子ORR反应的比例较高。石墨烯包覆的金属Fe/Fe₃C纳米晶生长N-CNTs后, 材料的导电性有所提高, 并且Fe-N_x活性位点在Fe/Fe₃C纳米颗粒表面分布均匀, 改善了材料的电化学活性。本研究为非贵金属氧还原电催化剂的继续深入研究以及广泛应用于商业化生产提供了一定的借鉴和依据。     

氮掺杂石墨烯原位生长碳纳米管复合过渡金属催化剂的制备及电催化性能EI北大核心CSCD

采用直接热解法,以石墨烯为载体,2-甲基咪唑锌盐MAF-4(ZIF8)为模板,尿素提供碳和氮源,Fe为过渡金属源,合成氮掺杂石墨烯(N/GO)和Fe-ZIF8(N-GO@Fe/ZIF8)的复合催化剂,并组装成锌空气电池。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)及电化学工作站等分析手段对催化剂的形貌、结构及电化学性能进行表征。结果表明:合成的N-GO@Fe/ZIF8-900催化剂具有优异的氧还原/氧析出(ORR/OER)性能。氧还原半波电位达到0.885 V,优于Pt/C(0.856 V),氧析出时,在10 mA/cm^(2)的电流密度下对应电位为1.811 V,优于贵金属Pt/C(1.968 V),与IrO_(2)(1.75 V)性能相当。组装成锌空气电池后,比能量和功率密度分别达到886.2 mW·h·g^(-1)和73.44 mW/cm^(2),高于贵金属Pt/C的比能量(791.04 mW·h·g^(-1))和功率密度(57.12 mW/cm^(2))。     

CoSeO3化合物的制备及对阴极氧还原的催化性能

以Co₄(CO)₁₂和Se为原料, 采用低温回流方法在乙二醇介质中合成了CoSeO₃化合物。利用扫描电镜(SEM)、X射线衍射仪(XRD)和旋转圆盘电极(RDE)技术表征合成的化合物微观形貌、结构特征和电化学性能。这种化合物主要由单斜结构的CoSeO₃•H₂O晶粒组成, 粒径大小约为26.7 nm, 具有规则的晶体外形。在25℃, 0.5 mol/L H₂SO₄电解液中, CoSeO₃化合物对氧还原反应(ORR)表现出明显的电催化活性, 开路电位为0.80 V(vs NHE)。根据Koutecky-Levich方程计算出每个氧分子还原过程转移的电子数约为3.8。在0.64~0.76 V(vs NHE)电位范围内, 测得催化剂的传递系数、Tafel斜率和交换电流密度分别为0.50、119 mV和1.98×10^-6 mA/cm²。CoSeO₃化合物的催化活性和电化学稳定性也与商品Pt催化剂进行了比较。     

N,P Co‐Coordinated Manganese Atoms in Mesoporous Carbon for Electrochemical Oxygen Reduction

The increasing interest in fuel cell technology encourages the development of efficient and low‐cost electrocatalysts to replace the Pt based materials for catalyzing the cathodic oxygen reduction reaction (ORR). In the present work, a nitrogen and phosphorus co‐coordinated manganese atom embedded mesoporous carbon composite (MnNPC‐900) is successfully prepared via a polymerization of o‐phenylenediamine followed by calcination at 900 °C. The MnNPC‐900 composite shows a high ORR activity in alkaline media, offering an onset potential of 0.97 V, and a half‐wave potential of 0.84 V (both vs reversible hydrogen electrode) with a loading of 0.4 mg cm^?2. This performance not only exceeds its phosphorus‐free counterpart (MnNC‐900), but also is comparable to the Pt/C catalyst under identical measuring conditions. The significantly enhanced ORR performance of MnNPC‐900 can be ascribed to: i) the introduction of phosphorus assists the generation of mesopores during the pyrolysis and endows the MnNPC‐900 composite with large surface area and pore volume, thus facilitating the mass transfer process and increases the number of exposed active sites. ii) The formation of N,P co‐coordinated atomic‐scale Mn sites (MnN_xP_y), which modifies the electronic configuration of the Mn atoms and thereby boosts the ORR catalytic activity.     

Mn-doped perovskite-type oxide LaFeO3 as highly active and durable bifunctional electrocatalysts for oxygen electrode reactions

Perovskite oxides based on the alkaline earth metal lanthanum for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolytes are promising catalysts, but their catalytic activity and stability remain unsatisfactory. Here, we synthesized a series of LaFe_1−xMn_xO₃ (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1) perovskite oxides by doping Mn into LaFeO₃ (LF). The results show that the doping amount of Mn has a significant effect on the catalytic performance. When x = 0.5, the catalyst LaFe_0.5Mn_0.5O₃ (LFM) exhibits the best performance. The limiting current density in 0.1 mol·L⁻¹ KOH solution is 7 mA·cm⁻², much larger than that of the commercial Pt/C catalyst (5.5 mA·cm⁻²). Meanwhile, the performance of the doped catalyst is also superior to that of commercial Pt/C in terms of the long-term durability. The excellent catalytic performance of LFM may be ascribed to its abundant O²⁻/O⁻ species and low charge transfer resistance after doping the Mn element.     

LaNiO3 modified with Ag nanoparticles as an efficient bifunctional electrocatalyst for rechargeable zinc--air batteries

No-precious bifunctional catalysts with high electrochemical activities and stability were crucial to properties of rechargeable zinc–air batteries. Herein, LaNiO₃ modified with Ag nanoparticles (Ag/LaNiO₃) was prepared by the co-synthesis method and evaluated as the bifunctional oxygen catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Compared with LaNiO₃, Ag/LaNiO₃ demonstrated the enhanced catalytic activity towards ORR/OER as well as higher limited current density and lower onset potential. Moreover, the potential gap between ORR potential (at −3 mA·cm⁻²) and OER potential (at 5 mA·cm⁻²) was 1.16 V. The maximum power density of the primary zinc–air battery with Ag/LaNiO₃ catalyst achieved 60 mW·cm⁻². Furthermore, rechargeable zinc–air batteries operated reversible charge–discharge cycles for 150 cycles without noticeable performance deterioration, which showed its excellent bifunctional activity and cycling stability as oxygen electrocatalyst for rechargeable zinc–air batteries. These results indicated that Ag/LaNiO₃ prepared by the co-synthesis method was a promising bifunctional catalyst for rechargeable zinc–air batteries.     

A simple synthesis method for nanostructured Co-WC/carbon composites with enhanced oxygen reduction reaction activity

Co nanoparticles (Co NPs) and nanoscale tungsten carbide (WC) are successfully synthesized simultaneously with mesoporous structured carbon black (C) using an innovative simple method, which is known as solution plasma processing (SPP), and NPs are also loaded onto carbon black at the same time by SPP. The introduction of Co NPs led to not only superior oxygen reduction reaction (ORR) activity in terms of onset potential and peak potential, but also to a more efficient electron transfer process compared to that of pure WC. Co-WC/C also showed durability for long-term operation better than that of commercial Pt/C. These results clearly demonstrate that the presence of Co NPs significantly enhanced the ORR and charge transfer number of neighboring WC NPs in ORR activities. In addition, it was proved that SPP is a simple method (from synthesis of NPs and carbon black to loading on carbon black) for the large-scale synthesis of NP-carbon composite. Therefore, SPP holds great potential as a candidate for next-generation synthetic methods for the production of NP-carbon composites.     

High-performance oxygen reduction and evolution carbon catalysis: From mechanistic studies to device integration

The development of high-performance and low-cost oxygen reduction and evolution catalysts that can be easily integrated into existing devices is crucial for the wide deployment of energy storage systems that utilize O2-H2O chemistries,such as regenerative fuel cells and metal-air batteries.Herein,we report an NH3-activated N-doped hierarchical carbon (NHC) catalyst synthesized via a scalable route,and demonstrate its device integration.The NHC catalyst exhibited good performance for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER),as demonstrated by means of electrochemical studies and evaluation when integrated into the oxygen electrode of a regenerative fuel cell.The activities observed for both the ORR and the OER were comparable to those achieved by state-of-the-art Pt and Ir catalysts in alkaline environments.We have further identified the critical role of carbon defects as active sites for electrochemical activity through density functional theory calculations and high-resolution TEM visualization.This work highlights the potential of NHC to replace commercial precious metals in regenerative fuel cells and possibly metal-air batteries for cost-effective storage of intermittent renewable energy.     

Core–shell nanostructure supported Pt catalyst with improved electrocatalytic stability in oxygen reduction reaction

Core–shell nanostructure electrode (TiO₂@C) for oxygen reduction reaction is prepared with TiO₂ nanoparticles at 900 °C in a methane atmosphere. The TiO₂@C supported Pt catalyst (Pt/TiO₂@C) contains Pt nanoparticles on TiO₂@C nanostructure electrodes consisting of TiO₂ as a core and carbon as a shell. In the accelerated stability test, the Pt/TiO₂@C exhibits a superior ORR stability to conventional carbon supported Pt catalyst. It is likely that the enhanced catalytic properties of the nanostructure supported Pt catalyst may be due to graphite-like carbon and an improved electronic conductivity of the core–shell nanostructure.