高CO耐性的金属间PtBi纳米片用于甲醇电氧化

我们通过热注入的方法制备了一种高CO耐性的金属间PtBi纳米片。所制备的金属间PtBi纳米片在甲醇氧化反应(MOR)中展现出优异的催化性能和良好的稳定性能，最大的质量活性高达4.09 A·mg_Pt^-1，接近商业Pt/C的3.2倍。计时电流-时间(I-t)稳定性测试之后，活性仅仅衰减5.7%，远低于商业Pt/C。CO吸附-脱附(CO-Stripping)曲线和循环伏安演变(CV-Evolution)曲线证实了金属间PtBi纳米片高的CO耐受性。     

高载量PtNi金属间化合物的氧还原电催化性能

采用改进的多元醇法制备了PtNi(原子比1∶1)质量分数为60%的高金属载量碳载PtNi合金(PtNi/C), 通过在450 ℃下退火处理获得了碳载PtNi金属间化合物氧还原电催化剂. 该催化剂对氧还原的质量比活性和面积比活性分别是商业化Pt/C(JM Pt/C)催化剂的1.66和2.3倍; 并且加速耐久性测试后PtNi金属间化合物催化剂的质量比活性仍与Pt/C的初始性能相当, 耐久性得到了大幅提升. PtNi/C金属间化合物催化剂氧还原活性和稳定性的提高归因于PtNi的有序原子排布结构及催化剂表面零价金属含量的提高.     

Au/Si 载体负载单层Pt 催化剂的制备及其电催化性能的研究

以Si 纳米粉为载体, 通过化学镀的方法在其表面部分沉积纳米Au 颗粒后, 再通过欠电位的方法在Au 颗粒表面沉积了单层及亚单层的Pt. 通过透射电子显微镜(TEM), 循环伏安(CV)等方法对所制备的Pt/Au/Si 催化剂进行了形貌及电化学性能的表征. 结果表明, 该单层Pt 覆盖的Au/Si 催化剂对于甲醇的质量电催化活性是商业E-TEK(Pt/C)的8 倍,相比于不同层数的Pt, 单层覆盖时Pt 的利用率最高, 该单层Pt 负载Au/Si 催化剂对于抑制CO 的中毒的性能也比商业E-TEK(Pt/C)有明显的提高.     

凹形树突状PtCu纳米催化剂的合成及对甲醇的电催化

以邻苯二胺为表面活性剂,通过水热釜法一步制备凹形树突状PtCu双金属纳米催化剂(PtCu NCDs)。PtCu NCDs在电催化甲醇氧化(MOR)的应用中表现出非常高的活性和很强的抗有毒中间体作用。PtCu NCDs对于甲醇氧化的质量活性为(0.53 A·mg^-1 Pt)是商业Pt/C(0.26 A·mg^-1 Pt)的2.04倍。从比活性的CV曲线图对比发现PtCu NCDs(1.07 mA·cm^-2)是商业Pt/C(0.55 mA·cm^-2)的1.95倍。而且,PtCu NCDs(2.76)比商业Pt/C催化剂(1.02)表现出更高的I_f/I_b比值。这些优异的电催化活性可能归功于PtCu NCDs特殊的凹形树突状形貌。     

膨胀石墨负载纳米Pt催化剂的制备及其电催化性能

以天然鳞片石墨为基材,采用高氯酸插层氧化制备了膨胀石墨(EG),利用乙二醇液相还原法在其表面负载了Pt纳米颗粒;采用XRD、TEM、SEM及循环伏安曲线(CV)等手段对其形貌、结构及对甲醇的电催化性能进行了表征研究。结果表明,Pt纳米颗粒的平均粒径为2.56 nm,均匀地分布在膨胀石墨载体表面,而片状结构的膨胀石墨载体能明显提升其电催化活性和抗CO中毒性能;相同条件下,该膨胀石墨负载纳米Pt催化剂的质量活性比和电流密度分别是商用JM Pt/C的1.24倍和1.5倍。     

凹形树突状PtCu纳米催化剂的合成及对甲醇电催化的研究

以邻苯二胺为表面活性剂,通过水热釜法一步制备凹形树突状PtCu双金属纳米催化剂(PtCu NCDs)。PtCu NCDs在电催化甲醇氧化(MOR)的应用中表现出非常高的活性和很强的抗有毒中间体作用。PtCu NCDs对于甲醇氧化的质量活性为(0.53 A·mg^-1 Pt)是商业Pt/C(0.26 A·mg^-1 Pt)的2.04倍。从比活性的CV曲线图对比发现PtCu NCDs(1.07 mA·cm^-2)是商业Pt/C(0.55 mA·cm^-2)的1.95倍。而且,PtCu NCDs(2.76)比商业Pt/C催化剂(1.02)表现出更高的I_f/I_b比值。这些优异的电催化活性可能归功于PtCu NCDs特殊的凹形树突状形貌。     

可见光诱导提升Pt/g-C3N4纳米片甲酸氧化性能的研究

以半导体材料类石墨氮化碳纳米片(g-C₃N₄纳米片)为载体,通过微波-多元醇法构筑了Pt/g-C₃N₄纳米片催化剂. 通过TEM、XRD、XPS、紫外-可见吸收光谱等方法对Pt/g-C₃N₄纳米片催化剂的粒径尺寸、组成、结构、光学等性质进行分析. 通过对比可见光照和暗室条件下的甲酸电氧化活性,Pt/g-C₃N₄纳米片催化剂在可见光照射下展现出良好的催化性能. 该性能的提高一方面可能是由于g-C₃N₄纳米片在可见光照射下加速了电子从Pt转移给g-C₃N₄纳米片,Pt处于“电子匮乏”状态,可削弱CO与Pt之间的化学键能,减弱CO在Pt表面的吸附能力,促进了CO的氧化,提高了催化剂抗中毒能力;另一方面,g-C₃N₄纳米片在光照条件下分离出的空穴可有效氧化甲酸分子,提高甲酸氧化活性. 因此,可见光条件下可有效提高Pt/g-C₃N₄纳米片催化剂甲酸催化氧化活性,这为直接甲酸燃料电池的发展提供了新思路.     

高活性甲醇氧化电催化剂Pt-Pd纳米合金的组分可控合成

Pt纳米粒子由于其本身独特的物理、化学性质以及能够同时促进氧化和还原反应,在工业生产和商业设备中(尤其在直接甲醇燃料电池中)广泛用作重要的电催化剂.然而,Pt作为贵金属在自然界中的含量极其稀少,价格昂贵;另外,甲醇氧化反应中产生的中间产物CO很容易市Pt纳米粒子中毒而失活.因此,迫切需要一种Pt用量少,催化性能高的材料.一制备高活性比表面积的Pt纳米颗粒,可以有效提高Pt利用率.另外,调控纳米粒子使其裸露特定的晶面、边、角以及缺陷也能有效提升催化性能.还可以采用Pt纳米粒子结合其它金属元素形成双金属合金,如,Pt-M (M = Pd,Au,Ag,Ru,Fe,Co,Ni,等)催化剂,可以在减少Pt元素用量的同时有效提升催化活性.在众多可供选择的元素中,Pd相对于Pt价格低廉,但两者具有相近的物理、化学性质以及较高的电催化性能,使Pt-Pd纳米合金呈现十分优异的电催化性能.研究表明,Pt-Pd纳米合金在酸性和CO环境中能有效催化有机小分子电氧化过程.另外,在酸性环境中,用Pd替代Cu,Ag,Co或Ni,可以有效减少催化剂的腐蚀.本文在乙二醇溶液中同时还原K2PtCl4和Na2PdCl4,在110 ℃C反应5 h制备出超细的Pt-Pd纳米合金.通过X射线衍射(XRD)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)以及能谱仪(EDS)对合金进行表征,从而确定产物为尺寸4 nm左右的Pt-Pd纳米合金,且通过改变金属前驱体的投料比可以有效调控Pt-Pd合金组分(按元素比例分别表示为Pt1Pd3,Pt1Pd1,Pt3Pd1).采用循环伏安法、线性扫描伏安法以及计时安培法等多种手段测试样品在0.5 mol/L H2SO4和0.5 mol/L CH3OH的酸性环境中(50 mV/s)电化学性能,并与商业Pt/C进行比较.结果表明,合金的催化性能和组分密切相关,当Pt元素的含量为75%左右时,Pt-Pd纳米合金表现出最佳的催化活性和稳定性,其中Pt3Pd1的电催化质量活性可达商业Pt/C的7倍之多.我们把Pt-Pd纳米合金的催化性能对其组分的依赖性归结为甲醇氧化反应中的双官能团机制,反应中,Pt可有效催化甲醇脱氢产生Pt-CO,Pd则催化水脱氢形成Pd-OH.当Pd含量减少时,Pt表面的水脱氢反应只有在高电位才能发生,从而降低催化效率;而Pd含量过多,则会抑制Pt催化甲醇的脱氢反应,使催化效率大大降低.因此,只有适宜Pt/Pd比例,才能有效提升催化效率.     

SiC/Pt/CdS纳米棒Z型异质结的制备及其高效光催化产氢性能（英文）

本文采用简单的化学还原辅助水热法制备了一种新型Si C/Pt/Cd SZ型异质结纳米棒,并将Pt纳米粒子锚定在Si C纳米棒与Cd S纳米粒子的界面间,诱导电子-空穴对沿着Z型迁移路径进行转移。进行一系列的表征来分析该催化体系的结构,形貌和性能。X射线衍射(XRD)和X射线光电子能谱(XPS)结果表明,成功合成了具有较好晶体结构的光催化剂。通过透射电子显微镜证明,Pt纳米颗粒生长在Si C纳米棒和Cd S纳米颗粒的界面间。UV-Vis漫反射光谱显示,所制备的Z-型异质结样品具有比原始Cd S材料更宽的光吸收范围。光致发光光谱和瞬态光电流响应进一步证明具有最佳摩尔比的Si C/Pt/Cd S纳米棒样品具有最高的电子-空穴对分离效率。通过控制Si C和Cd S的摩尔比,可以有效地调节Si C/Pt纳米棒表面Cd S的负载量,从而使得Si C/Pt/Cd S纳米棒光催化剂达到最佳性能。当Si C:Cd S=5:1 (摩尔比)时可以达到最佳产氢性能,其最大析氢速率达到122.3μmol·h~(-1)。此外,从扫描电子显微镜、XRD和XPS分析可以看出,经过三次循环测试后,Si C/Pt/Cd S光催化剂的形貌和晶体结构均基本保持不变,表明Si C/Pt/Cd S纳米复合材料在可见光下产氢时具有稳定的结构。通过选择性光沉积技术在光反应中同时进行Au纳米粒子的光还原沉积和Mn3O4纳米粒子光氧化沉积以证明电子-空穴对的Z-型转移机制。实验结果表明,Cd S导带上的电子主要参与光催化过程中的还原反应,Si C价带上的空穴更容易发生氧化反应,其中,Si C的导带上的电子将与Cd S价带上的空穴复合形成Z型传输路径。因此,提出了在光催化产氢过程中Si C/Pt/Cd S纳米棒催化体系可能的Z-型电荷迁移路径来解释产氢活性的提高。该研究为基于Si C纳米棒的Z-型光催化体系的合成提供了新的策略。基于以上分析,Si C/Pt/Cd S纳米复合材料具有高效、廉价、易于制备、结构稳定等优势,具有突出的商业应用前景。     

氧化铁对铂在碱性介质中催化氧化甲醇的促进作用（英文）

Pt催化剂是电催化领域用途最为广泛的贵金属催化剂.Pt资源稀缺,价格昂贵,同时它的物理化学特性又决定了其在多种催化反应中难以被替代.在质子交换膜燃料电池的小分子醇类电氧化过程中,难免存在Pt的毒化现象,其催化性能有待进一步提升.因此,围绕着Pt催化剂纳米结构的设计、抗毒性及反应机理的探索一直是电催化研究面临的重要课题.目前,已被广泛认可的提高Pt催化性能的方法之一是引入第二种金属,通过金属间协同效应(双功能机理)、张力效应或电子效应等对Pt的催化行为进行改性.对于由双/多金属组成的纳米结构催化剂,无论是协同效应还是电子效应,催化活性的提高都需要金属间有丰富的接触界面和恰当的邻近状态.通过调变两组元的种类、原子比和接触状态等可以实现对金属-金属界面的调控,进而调变催化剂性能.除金属助剂外,金属氧化物对Pt催化剂的助催化作用也引起广泛关注.由于金属氧化物与Pt之间的密切接触作用,氧化物的形貌特点对Pt的催化性能可产生重要影响.到目前为止,有关催化剂形貌效应的研究主要集中于贵金属纳米颗粒上(Pt,Au,Pd等),但关于金属氧化物载体/助剂的形貌对贵金属催化性能影响的研究尚不多.具有明确形貌的金属氧化物载体/助剂,暴露的晶面不同,表面原子的配位状态也不同,从而造成与之密切接触的Pt的性质发生改变.因此,金属氧化物的表面性质以及Pt-金属氧化物的界面性质将对电催化性能产生重要影响,深入阐释贵金属-金属氧化物的表/界面性质以及建立有效的构效关系,对设计和制备高效电催化剂具有一定的指导意义.为了提高Pt基催化剂活性、抗CO中毒能力以及稳定性,本文采用共沉淀法和水热法分别制备了纳米棒和六边形纳米片状的Fe_2O_3作为Pt催化剂的助剂,考察了助剂形貌对Pt催化剂在碱性介质中催化氧化甲醇的促进作用.通过X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱以及电化学技术对催化剂进行了表征.结果显示,Fe_2O_3的存在能显著提高Pt催化剂在碱性介质中对甲醇氧化的电催化性能,而且以Fe_2O_3纳米棒为助剂制备的Pt-Fe_2O_3/C-R催化剂催化活性以及稳定性比Fe_2O_3纳米片为助剂制备的Pt-Fe_2O_3/C-P催化剂更高.这种促进效应可能与助剂Fe_2O_3的形态有关.Pt-Fe_2O_3/C-R催化剂中Pt的质量比活性为5.32 A/mgPt,本征活性为162.7 A/m2Pt,分别是Pt-Fe_2O_3/C-P催化剂的1.67和2.04倍,是商业PtRu/C样品的4.19和6.16倍.协同效应和电子效应是Pt催化性能提升的主要原因.此外,Pt-Fe_2O_3/C-R样品中高价态Pt的含量较高,可能也是加速甲醇氧化反应动力学的原因之一.高价态的Pt可能会增强甲醇分子在Pt表面的吸附强度,促进Pt上甲醇氧化反应初始步.这些发现不仅可对甲醇电催化氧化机理有了更深的理解,而且对设计和制备高性能甲醇氧化电催化剂也具有一定的指导意义.     

Electrocatalytic mechanism and kinetics of SOMs oxidation on ordered PtPb and PtBi intermetallic compounds: DEMS and FTIRS study

The electrocatalytic activities and mechanisms of PtPb and PtBi ordered intermetallic phases towards formic acid, formaldehyde and methanol oxidation have been studied by DEMS and FTIRS, and the results compared to those for a pure polycrystalline platinum electrode. While PtPb exhibits an enhanced electrocatalytic activity for the oxidation of all three organic molecules when compared to a Pt electrode, PtBi exhibits an enhanced catalytic activity towards formic acid and formaldehyde oxidation, but not methanol. FTIRS data indicate that adsorbed CO does not form on PtPb or PtBi intermetallic compounds during the oxidation of formic acid, formaldehyde and methanol, and therefore their oxidation on both PtPb and PtBi intermetallic compounds proceeds via a non-CO(ads) pathway. Quantitative DEMS measurements indicate that only CO(2) was detected as a final product during formic acid oxidation on Pt, PtPb and PtBi electrodes. At a smooth polycrystalline platinum electrode, the oxidation of formaldehyde and methanol produces mainly intermediates (formaldehyde and formic acid), while CO(2) is a minor product. In contrast, CO(2) is the major product for formaldehyde and methanol oxidation at a PtPb electrode. The high current efficiency of CO(2) formation for methanol and formaldehyde oxidation at a PtPb electrode can be ascribed to the complete dehydrogenation of formaldehyde and formic acid due to electronic effects. The low onset potential, high current density and high CO(2) yield make PtPb one of the most promising electrocatalysts for fuel cell applications using small organic molecules as fuels.     

Pd-Enriched-Core/Pt-Enriched-Shell High-Entropy Alloy with Face-Centred Cubic Structure for C1 and C2 Alcohol Oxidation

High-entropy alloy nanoparticles (HEA NPs) have aroused great interest globally with their unique electrochemical, catalytic, and mechanical properties, as well as diverse activity and multielement tunability for multi-step reactions. Herein, a facile low-temperature synthesis method at atmospheric pressure is employed to synthesize Pd-enriched-HEA-core and Pt-enriched-HEA-shell NPs with a single phase of face-centred cubic structure. Interestingly, the lattice of both Pd-enriched-HEA-core and Pt-enriched-HEA-shell enlarge during the formation process of HEA, with tensile strains included in the core and shell of HEA. The as-obtained PdAgSn/PtBi HEA NPs show excellent electrocatalytic activity and durability for methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). The specific (mass) activity of PdAgSn/PtBi HEA NPs for MOR is 4.7 mA cm⁻² (2874 mA mg_(Pd+Pt)⁻¹), about 1.7 (5.9) and 1.5 (4.8) times higher than that of commercial Pd/C and Pt/C catalysts, respectively. Additional to high-entropy effect, Pt sites and Pd sites on the interface of the HEA act synergistically to facilitate the multi-step process towards EOR. This study offers a promising way to find a feasible route for scalable HEA manufacturing with promising applications.     

Synergistic Enhancement of Electrocatalytic Activity toward Oxygen Reduction Reaction in Alkaline Electrolytes with Pentabasic (Fe,B, N,S, P)‐Doped Reduced Graphene Oxide

As alternatives to Pt‐based electrocatalysts, the development of nonprecious metal catalysts with high performance in the cathodic oxygen reduction reaction (ORR) is highly desirable for widespread use in fuel cells. Here we report a simple approach for preparing pentabasic (Fe, B, N, S, P)‐doped reduced graphene oxide (rGO) via a two‐step doping method of adding boric acid and ferric chloride to ternary (N, S, P)‐doped rGO (NSPG). Electrochemical investigation of the composites for the ORR revealed that simultaneously doping appropriate amounts of Fe and B into the NSPG produced a synergistic effect that endowed the prepared catalyst with both a positively shifted ORR half‐wave potential and high selectivity for the 4e^? reduction of O₂. The optimized Fe₂B‐NSPG catalyst approached a 4e^? process for the ORR with a half‐wave potential (E_1/2=0.90 V vs. RHE) even 30 mV higher than that of the commercial Pt/C catalyst in alkaline solution. Furthermore, relative to the Pt/C catalyst, the Fe₂B‐NSPG demonstrated superior stability and excellent tolerance of the methanol cross‐over effect. This simple method afforded pentabasic (Fe, B, N, S, P)‐doped rGO as a promising nonprecious metal catalyst used for alkaline fuel cells.     

Magnetic N‐Enriched Fe3C/Graphitic Carbon instead of Pt as an Electrocatalyst for the Oxygen Reduction Reaction

A series of Fe₃C/C‐N_x nanoparticles (NPs) with different nitrogen content are prepared by a simple one‐pot route. In the synthetic procedure, aniline and acetonitrile are simultaneously used as the carbon and nitrogen source. The effect of calcination temperature on the structural and functional properties of the materials is investigated. Magnetic measurement shows that the sample prepared at 800 °C (Fe₃C/C‐N₈₀₀ NPs) possesses the highest M_s value of 77.2 emu g^?1. On testing as oxygen reduction reaction (ORR) catalysts, the sample prepared at 750 °C (Fe₃C/C‐N₇₅₀ NPs) shows the best ORR performance among the series, with a more positive onset potential (+0.99 V vs. RHE), higher selectivity (number of electron transfer n≈3.93), longer durability, and stronger tolerance against methanol crossover than commercial Pt/C catalysts in a 0.1 m KOH solution. Moreover, in acidic solution, the excellent ORR activity and stability are also exhibited.     

Surface Iron Species in Palladium–Iron Intermetallic Nanocrystals that Promote and Stabilize CO2 Methanation

It is of pivotal importance to develop efficient catalysts and investigate the intrinsic mechanism for CO₂ methanation. Now, it is reported that PdFe intermetallic nanocrystals afforded high activity and stability for CO₂ methanation. The mass activity of fct‐PdFe nanocrystals reached 5.3 mmol g^?1 h^?1, under 1 bar (CO₂:H₂=1:4) at 180 °C, being 6.6, 1.6, 3.3, and 5.3 times as high as that of fcc‐PdFe nanocrystals, Ru/C, Ni/C, and Pd/C, respectively. After 20 rounds of successive reaction, 98 % of the original activity was retained for PdFe intermetallic nanocrystals. Further mechanistic studies revealed that PdFe intermetallic nanocrystals enabled the maintenance of metallic Fe species via a reversible oxidation–reduction process in CO₂ methanation. The metallic Fe in PdFe intermetallic nanocrystals induced the direct conversion of CO₂ into CO* as the intermediate, contributing to the enhanced activity.     

Surface Iron Species in Palladium–Iron Intermetallic Nanocrystals that Promote and Stabilize CO2 Methanation

It is of pivotal importance to develop efficient catalysts and investigate the intrinsic mechanism for CO₂ methanation. Now, it is reported that PdFe intermetallic nanocrystals afforded high activity and stability for CO₂ methanation. The mass activity of fct-PdFe nanocrystals reached 5.3 mmol g⁻¹ h⁻¹, under 1 bar (CO₂:H₂=1:4) at 180 °C, being 6.6, 1.6, 3.3, and 5.3 times as high as that of fcc-PdFe nanocrystals, Ru/C, Ni/C, and Pd/C, respectively. After 20 rounds of successive reaction, 98 % of the original activity was retained for PdFe intermetallic nanocrystals. Further mechanistic studies revealed that PdFe intermetallic nanocrystals enabled the maintenance of metallic Fe species via a reversible oxidation–reduction process in CO₂ methanation. The metallic Fe in PdFe intermetallic nanocrystals induced the direct conversion of CO₂ into CO* as the intermediate, contributing to the enhanced activity.     

Pyrolysis of Animal Bones with Vitamin B12: A Facile Route to Efficient Transition Metal–Nitrogen–Carbon (TM‐N‐C) Electrocatalysts for Oxygen Reduction

By pyrolyzing cattle bones, hierarchical porous carbon (HPC) networks with a high surface area (2520 m² g^?1) and connected pores were prepared at a low cost and large scale. Subsequent co‐pyrolysis of HPC with vitamin B12 resulted in the formation of three‐dimensional (3D) hierarchically structured porous cobalt–nitrogen–carbon (Co‐N‐HPC) electrocatalysts with a surface area as high as 859 m² g^?1 as well as a higher oxygen reduction reaction (ORR) electrocatalytic activity, better operation stability, and higher tolerance to methanol than the commercial Pt/C catalyst in alkaline electrolyte.     

B,N Co-Doped Three-Dimensional Carbon Aerogels with Excellent Electrochemical Performance for the Oxygen Reduction Reaction

Herein, an ordinary and mass-production approach is reported to synthesize boron (B) and nitrogen (N) co-doped three-dimensional (3D) carbon aerogels (CA) by using glucose and borax as the raw materials by a simple hydrothermal method and then carbonization in NH₃ atmosphere. The porous material (BN-CA-900) possesses a large specific surface area (1032 m² g⁻¹) and high contents of doped pyridinic N and graphitic N. The onset potential (0.91 V vs. reversible hydrogen electrode, RHE), half-wave potential (0.77 V vs. RHE), and current density (5.70 mA cm⁻² at 0.2 V vs. RHE) of BN-CA-900 for ORR are similar to those of commercial Pt/C, indicating that BN-CA-900 has a comparable catalytic activity with Pt/C in alkaline media. The number of electron transfer is 3.86–3.99 and the yield of hydrogen peroxide is less than 6.8 %. BN-CA-900 also presents decent catalytic performance in acidic medium. Moreover, the stability and methanol tolerance of BN-CA-900 are superior to commercial Pt/C in both alkaline and acidic media. The prepared BN-CA-900 is a promising candidate that may be applied in other areas, such as the adsorption of pollution, porous conductive electrodes, and lithium-ion batteries.