高效铂锰合金氧还原催化剂的制备及性能

以氮掺杂科琴黑(N-KB)为载体,采用浸渍还原法合成铂锰合金催化剂(Pt-Mn-N-KB)。通过透射电子显微镜、 X射线衍射仪、比表面测定仪和X射线光电子能谱等对催化剂的形貌、结构和表面组成等进行表征,并对催化剂在中性和碱性电解液中的氧还原性能进行测试。结果表明：Pt-Mn-N-KB催化剂上的Pt-Mn颗粒分散均匀且无团聚现象,平均粒径为1.6 nm。Pt-Mn-N-KB催化剂在碱性电解液中表现出的半波电位为0.884 V,起始电位接近1.01 V,在中性电解液中表现出的半波电位为0.686 V,起始电位为0.83 V,均优于商业铂碳Pt-C的。作为空气阴极应用于铝空气电池,在碱性电解液中表现出的超高功率密度为117.29 mW/cm²,在中性电解液中的为25.65 mW/cm²(中性),相对于商业铂碳Pt-C的分别提高32%和28%     

尿素热转化法制备Co-N-C及Co-Ti-N-C催化剂的氧还原活性和稳定性

以尿素为含氮前躯体,通过热转化法制备了质子交换膜燃料电池(PEMFC)氧还原催化剂Co-N-C及Co-Ti-N-C,考察了不同的尿素/金属比(R)、焙烧温度及钛含量等条件对Co-N-C及Co-Ti-N-C电催化剂氧还原催化活性和稳定性的影响。利用元素分析、热重、X射线衍射分析、X射线光电子能谱等方法对催化剂进行了表征,研究了催化剂的氧还原活性中心结构。结果表明,催化剂在热处理温度为800℃,尿素与金属Co的摩尔比R=12时的氧还原性能最佳,峰电位(Ep,c)达到0.142 V(vs.SCE)。催化剂Co-N-C经353 K硫酸溶液浸泡3 d后,催化剂Co-N-C的活性中心Co4N的含量增大,Ep,c正移至0.445 V(vs.SCE)。钛的掺杂没有改变催化剂的活性中心结构,明显提高了其在酸性介质中的稳定性。     

金属掺杂聚吡咯碳化物PPY-M的制备及其氧还原反应电催化活性

在Fe³⁺或Co²⁺存在下进行吡咯的聚合反应, 得到金属离子掺杂的聚吡咯, 并在N₂气氛下700℃碳化, 再将该碳化产物在900℃焙烧得到含有不同金属的复合催化剂PPY-M(M为不同的金属)。采用SEM、XRD等对催化剂的结构进行了表征。通过循环伏安和线性电位扫描等电化学手段, 研究了催化剂对氧还原(ORR)的电催化活性及其稳定性。结果表明, 掺杂金属钴的催化剂的活性最好, 在酸性溶液中ORR的起始电位达到0.54 V(vs SCE),电流密度为7.5 mA/mg@-0.3 V(vs SCE); 在碱性溶液中ORR的起始电位为-0.11 V(vs SCE),电流密度为5.7 mA/mg@-0.8 V。Fe或Co掺杂的聚吡咯碳化物对ORR具有较强的电催化活性, 而且制备过程简单、成本低, 有较重要的研究意义。     

用于电催化氧还原制备双氧水的催化剂的研究进展

H2 O2及其水溶液双氧水具有强氧化性,被广泛应用于造纸、污水处理和消毒等方面.全球对H2 O2的需求量与日俱增,但传统的蒽醌法工艺复杂、成本高、效率低,氢氧直接合成法又存在很大的安全隐患.因此,电催化氧还原这种新型、绿色且安全的原位合成H2 O2方法近年来受到广泛关注.氧还原反应(ORR)是多电子反应,中间体复杂且难以测量,机理研究困难.ORR存在两种竞争的反应路径,两电子路径得到H2 O2,而四电子路径生成H2O.两电子氧还原反应(2e-ORR)的反应效率取决于催化剂的活性、选择性和稳定性.目前贵金属基催化剂(如Au、Pd)对2e-ORR显示出较好的催化性能,但昂贵、稀缺的特性限制了它们的广泛应用.当前关于电催化氧还原制备H2 O2所用催化剂的研究主要集中于三方面:(1)减少贵金属的负载.将惰性金属与活性金属相结合,得到了许多性能优异的合金材料,如Pt-Hg等.(2)发展非贵金属催化剂.碳基催化剂的缺陷、表面氧官能团(C=O、C-O等)、杂原子掺杂(N-、S-等)和过渡金属掺杂(Co、Fe等)都能够提高H2O2的选择性与催化活性.(3)发展非贵金属复合催化剂.非贵金属复合物催化剂(如MnO2/C、CoS2/C)可促进电子转移,提高H2 O2的选择性.本文系统介绍了2e-ORR的机理及测试方法,简要总结了近年来用于2e-ORR制H2 O2的贵金属基催化剂、碳基催化剂和非贵金属复合催化剂的研究进展,并在此基础上对电催化氧还原制双氧水未来的研究方向进行了展望.     

纤维状多孔钙锰氧化物制备及其氧还原反应电催化活性

首次以海藻酸钙纤维为载体制得层状-钙钛矿结构的Ca₂MnO₄钙锰氧化物(Ca-Mn-O), 并以尖晶石结构的CaMn₃O₆为对比样, 测试了样品作为电化学氧还原催化剂(ORR)的性能。通过XRD、FE-SEM、TEM和BET对材料进行表征, 结果表明该层状-钙钛矿结构的氧化物具有内部相互交联的多孔网状结构和大的比表面积。电催化测试结果表明: Ca₂MnO₄氧化物具有明显的催化活性, 高的极限扩散电流密度、接近四电子氧化还原以及在碱性溶液中较低产率的过氧化氢, 说明这种廉价而丰富的ORR催化剂具有潜在的应用前景。Ca-Mn-O氧化物的催化活性(初始还原电位、极限电流密度以及电子转移数)很大程度依赖于表面Mn的氧化态和晶体结构。此外, 大的比表面积和多孔网状结构, 增多了氧还原反应的电催化活性位; 高的氧空位浓度有利于氧还原反应的进行; 合适的晶体结构具有开放的空间, 有利于氧的吸附。     

硼氮双掺杂提升碳点电催化氧还原活性研究

碳点(CDs)因其较大的比表面积和较快的电子转移特性,已成为能量转换应用领域一种新兴的纳米炭材料.本文以低成本的石油焦为原料,通过简便的一步电化学刻蚀方法制备了硼氮双掺杂碳点(BN-CDs).与单掺杂碳点B-CDs和N-CDs相比,双掺杂BN-CDs表现出更优异的四电子氧还原电催化活性,具有更正的起始电位(Eonset...     

PtIr/C合金催化剂的制备及其电催化性能

以碳黑(Vulcan XC 72)为载体,氯铱酸(H2IrCl6.6H2O)和氯铂酸(H2PtCl6.6H2O)为前驱体,聚乙烯基吡咯烷酮(PVP,polyvinylpyrrolidone)为保护剂,首次采用高压氢还原方法制备出PtIr/C合金催化剂,并对其进行不同温度的通H2热处理。运用XRD、TEM和XPS对PtIr/C合金催化剂进行表征。结果表明,Pt与Ir发生合金化,PtIr合金纳米粒子均匀分散在碳黑表面。经400和700℃热处理后,PtIr合金纳米粒子的平均粒径仅从4.46nm长大至4.56和5.58nm,且随着热处理温度的升高,其晶型不断完善。用CO-stripping伏安法,循环伏安法(CV)、计时电流法(CA)等电化学测试方法测试PtIr/C合金催化剂的电催化性能,发现400℃热处理的PtIr/C合金催化剂,在酸性溶液中对CO氧化的起始电位明显提前,对甲醇氧化具有最高的催化活性。     

PtMo合金催化剂氧还原反应催化性能研究

采用乙二醇还原法和后续的热处理工艺制备了Pt-Mo合金催化剂。使用透射电子显微镜、X射线衍射、电感耦合等离子体发射光谱、X射线光电子能谱等方法对样品进行了形貌、结构和组分的表征。通过电化学测试方法,探究了不同催化剂的电催化活性和稳定性。结果表明：合适的热处理温度不仅提高了Pt-Mo纳米颗粒的合金化程度,而且改变了催化剂颗粒表面的电子结构和成分。所以,经过400℃热处理的PtMo/C-400催化剂表现出较好的氧还原性能,其电催化活性和稳定性均与商业J01-Pt/C催化剂相当。     

用于氧还原反应的PtNi合金催化剂研究进展

氧还原反应是质子交换膜燃料电池阴极催化反应的关键步骤。氧还原活性趋势图(火山图)中,贵金属Pt超高的催化性能显而易见,因此目前氧还原性能最佳的商业化催化剂仍然是碳载铂(Pt/C)。另一方面,Pt昂贵的价格也促使国内外研究者尝试开发Pt合金催化剂、非Pt催化剂等新型催化剂。在开发低Pt催化剂过程中,通过添加过渡金属来改变d带中心是较普遍的解决方案。研究者发现PtNi/C催化剂的氧还原性能远超商业化Pt/C催化剂,但催化剂中的过渡金属Ni在酸性条件下易溶解,从而破坏反应环境,导致稳定性较差。当前针对该问题的研究主要聚焦于调节催化剂晶面、表面应变以及组成结构,通过改变这些因素试图提高催化剂的电化学活性和耐久性。其中,由Pt₃Ni(111)面封闭形成的八面体纳米颗粒已经被认为是很有前途的氧还原反应电催化剂,成为了PtNi双金属催化剂中的研究热点。此外,对合金表面进行其他金属/非金属元素修饰,改善催化剂载体性质,也可以实现催化剂氧还原性能的提高。本文综述了近些年用于氧还原反应的Pt-Ni基催化剂的研究现状,主要包括通过催化剂形貌调控来控制暴露晶面、对催化剂进行表面修饰,以及...     

氮掺杂再生活性炭的制备及电催化氧还原反应性能研究

为解决危废活性炭传统回收方式带来的资源浪费和环境污染等问题,本工作以抗生素脱色废活性炭为原料、氨气为氮源,采用高温热解再生法将氮元素通过sp²杂化键合进入到活性炭骨架中,制备了氮掺杂再生废活性炭氧还原反应(ORR)催化剂,分析了氮掺杂再生活性炭的物相组成、微观形貌、电化学性能。结果表明,当温度为1 000℃、退火时间为1 h时,所制备的N-RWAC-1000-1氧还原电催化性能最佳。N-RWAC-1000-1具有丰富的微孔和介孔结构,比表面积可达908 m²/g,在碱性介质中的起始电位为0.92 V(vs.RHE),半波电位为0.82 V(vs.RHE),均接近商业20%(质量分数)的铂碳催化剂。此外,氮掺杂再生炭拥有优于商业化铂碳的循环稳定性和甲醇耐受性,有望成为新的氧还原催化剂以期为抗生素脱色废活性炭的高值化利用提供了新的方向。     

蜂窝状碳负载铁基单原子催化剂的制备及ORR催化性能研究

单原子催化剂(SACs)以近100％的原子利用率以及优秀的催化活性等,在促进多相催化方面受到了广泛关注.然而,由于金属原子在高温下易烧结,SACs的合成仍然具有挑战性.本研究利用熔融盐(MS)提供的强极性环境,制备了以氮掺杂碳为载体的铁基单原子催化剂(Fe SA-NC).结果表明,Fe SA-NC显示出蜂窝状的多孔形貌...     

Activity Trends of Binary Silver Alloy Nanocatalysts for Oxygen Reduction Reaction in Alkaline Media

The electrocatalytic activity of Pt‐based alloys exhibits a strong dependence on their electronic structures, but a relationship between electronic structure and oxygen reduction reaction (ORR) activity in Ag‐based alloys is still not clear. Here, a vapor deposition based approach is reported for the preparation of Ag₇₅M₂₅ (M = Cu, Co, Fe, and In) and Ag_x Cu_100?x (x = 0, 25, 45, 50, 55, 75, 90, and 100) nanocatalysts and their electronic structures are determined by valence band spectra. The relationship of the d‐band center and ORR activity exhibits volcano‐shape behaviors, where the maximum catalytic activity is obtained for Ag₇₅Cu₂₅ alloys. The ORR enhancement of Ag₇₅Cu₂₅ alloys originates from the 0.12 eV upshift in d‐band center relative to pure Ag, which is different from the downshift in the d‐band center in Pt‐based alloys. The activity trend for these Ag₇₅M₂₅ alloys is in the order of Ag₇₅Cu₂₅ > Ag₇₅Fe₂₅ > Ag₇₅Co₂₅. These results provide an insight to understand the activity and stability enhancement of Ag₇₅Cu₂₅ and Ag₅₀Cu₅₀ catalysts by alloying.     

Biomass Derived N‐Doped Porous Carbon Supported Single Fe Atoms as Superior Electrocatalysts for Oxygen Reduction

Exploring sustainable and high‐performance electrocatalysts for the oxygen reduction reaction (ORR) is the crucial issue for the large‐scale application of fuel cell technology. A new strategy is demonstrated to utilize the biomass resource for the synthesis of N‐doped hierarchically porous carbon supported single‐atomic Fe (SA‐Fe/NHPC) electrocatalyst toward the ORR. Based on the confinement effect of porous carbon and high‐coordination natural iron source, SA‐Fe/NHPC, derived from the hemin‐adsorbed bio‐porphyra‐carbon by rapid heat‐treatment up to 800 °C, presents the atomic dispersion of Fe atoms in the N‐doped porous carbon. Compared with the molecular hemin and nanoparticle Fe samples, the as‐prepared SA‐Fe/NHPC exhibits a superior catalytic activity (E _1/2 = 0.87 V and J _k = 4.1 mA cm^?2, at 0.88 V), remarkable catalytic stability (≈1 mV negative shift of E _1/2, after 3000 potential cycles), and outstanding methanol‐tolerance, even much better than the state‐of‐the‐art Pt/C catalyst. The sustainable and effective strategy for utilizing biomass to achieve high‐performance single‐atom catalysts can also provide an opportunity for other catalytic applications in the atomic scale.     

Defect-Engineered Mesoporous Undoped Carbon Nanoribbons for Benchmark Oxygen Reduction Reaction

For large-scale fuel cell applications, it is significant to replace expensive Pt-based oxygen reduction reaction (ORR) electrocatalysts with nonprecious metal- or metal-free carbon-based catalysts with high activity. However, it is still challenging to deeply understand the role of intrinsic defects and the origin of ORR activity in pure nanocarbon. Therefore, a novel self-assembly and a pyrolysis strategy to fabricate defect-rich mesoporous carbon nanoribbons are presented. Due to the effective regulation of nanoarchitecture, a vast number of defective catalytic sites (edge defects and holes) are exposed, which thereby enhances the electron transfer kinetics and catalytic activity. Such undoped nanoribbons display a large half-wave potential of 0.837 V, excellent long-term stability, and exceptional methanol tolerance, surpassing the most undoped ORR catalysts and the commercial Pt/C (20 wt.%) catalyst. Structural characterizations and density functional theory (DFT) calculations confirm that the zigzag edge defects and the armchair pentagon at the hole defect are responsible for outstanding ORR performance.     

Graphene‐Supported Mesoporous Carbons Prepared with Thermally Removable Templates as Efficient Catalysts for Oxygen Electroreduction

Graphene‐supported mesoporous carbons with rich nitrogen self‐doped active sites (N‐MC/rGO) are prepared by direct pyrolysis of a graphene‐oxide‐supported polymer composite embedded with massive, evenly distributed amorphous FeOOH that serve as efficient thermally removable templates. The resulting N‐MC/rGO catalysts exhibit high surface areas and apparent electrocatalytic activity for oxygen reduction reaction in alkaline media. Among the series, the sample prepared at 800 °C displays the best performance with a more positive onset potential, higher limiting currents, much higher stability, and stronger poison resistance than commercial Pt/C. This is ascribed to the synergetic functions of the highly conductive graphene support and the mesoporous N‐doped carbons that effectively impede the restacking of the graphene sheets and enhance the exposure of the rich nitrogen self‐doped active sites.     

2D Boron Imidazolate Framework Nanosheets with Electrocatalytic Applications for Oxygen Evolution and Carbon Dioxide Reduction Reaction

Ultrathin 2D materials possess unique properties that translate to enhanced efficiency as electrocatalysts, stimulating research toward methodologies that support their preparation. Herein, a two‐step strategy is reported that involves the preparation of the new boron imidazolate framework ( BIF‐73 ) which is subsequently utilized as a precursor to yield the crystalline 2D nanosheet material ( Fe@BIF‐73‐NS ) via post‐synthetic modification. This new electrocatalytic material stabilizes ultra‐small (Fe₂O₃) fragments resulting in an excellent electrocatalytic performance for the oxygen evolution reaction (OER: lower overpotential with 291 mV at the current density of 10 mA cm^?2) and carbon dioxide reduction reaction (faradaic efficiency of CO reaching 88.6% at ?1.8 V vs Ag/AgCl) without the need for noble metals. Additionally, theoretical calculations and microscopy reveal that the superior OER performance can be attributed to the increased exposure of binding sites within the material to which the catalytically active Fe³⁺ centers are bound through a post‐synthetic modification procedure. A red‐shift of the Fermi level around the valence band is observed and is proposed to be a result of the aforementioned interactions. This work opens an avenue toward the development of 2D functional metal organic framework nanosheets for energy conversion applications.     

Nano‐Intermetallic AuCu3 Catalyst for Oxygen Reduction Reaction: Performance and Mechanism

This paper introduces a new approach for catalyst design using the non‐precious metal Cu as one of the catalytic active centers. This differs from previous studies that considered precious metals to be responsible for the catalytic reaction in precious alloys. Intermetallic AuCu₃/C nanoparticles with a diameter of 3 nm were developed for the first time, with uniform dispersion and a narrow size distribution. The ca. 3 nm as‐synthesised AuCu₃/C showed superior catalytic performance for oxygen reduction reactions (ORR) in alkaline solutions, with comparable half‐wave potential and 1.5 times mass current density of commercial Pt/C at 0.80 V (vs. reversible hydrogen electrode (RHE)). The advanced catalytic activities are mainly attributed to the synergetic effects of electro‐active atomic Au and Cu on the particle surface, in which Cu helps to activate the O₂ molecule and Au benefits OH^? desorption. The excellent durability and methanol tolerance exhibited in alkaline solutions provide another advantage for AuCu₃/C to be considered as a potential alternative cathode catalyst in alkaline fuel cells.     

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。