Fabrication of Ultrafine Palladium Phosphide Nanoparticles as Highly Active Catalyst for Chemoselective Hydrogenation of Alkynes

Monodisperse palladium phosphide nanoparticles (Pd–P NPs) with a smallest size ever reported of 3.9 nm were fabricated using cheap and stable triphenylphosphine as phosphorous source. After the deposition and calcination at 300 °C and 400 °C, the resulting Pd–P NPs increased in size to 4.0 nm and 4.8 nm, respectively. Notably, the latter NPs probably crystallized with a single phase of Pd₃P_0.95, which acted as a highly active catalyst in semi‐ and stereoselective hydrogenation of alkynes. X‐ray photoelectron spectroscopy analysis determined a positive shift of binding energy for Pd(3d) in Pd–P NPs compared to that in Pd on carbon. It indicated the electron flow from metal to phosphorus and the larger electron deficiency of Pd in Pd–P NPs, which suppressed palladium hydride formation and subsequently increased the selectivity. Thus, this result may also indicate the applications of Pd–P and other metal–P NPs in various selective hydrogenation reactions.     

Construction of a MOF-Supported Palladium Catalyst via Metal Metathesis

A new MOF-supported heterogeneous palladium catalyst Pd/NBB-1 has been synthesized successfully through the effective metal metathesis between Pd(CF₃COO)₂ and NBB-1. NBB-1 is a two-dimensional zinc metal-organic framework constructed from 2-aminoterephthalate (NH₂−H₂BDC) and 2,2′-bipyridine-5-carboxylate (HBPC) by solvothermal method. The replacement efficiency of Pd(II) to Zn(II) is up to 72% after only 24 hours, which is beneficial to the catalytic application. Pd/NBB-1 with a low loading of 2 mol% works efficiently in the 1,4-addition reaction of arylboronic acids with α,β-unsaturated ketones in air, and its catalytic activity keeps unchanged after 3 reaction cycles. This work provides a new strategy to effectively prepare supported noble metal/MOF catalysts, which would further increase the practical applications of metal-organic frameworks.     

磷化镓纳米粒子的固氮

Under mild ambient conditions gallium phosphide （GAP） nanoparticles were employed to carry out the reduction of nitrogen. By using Nessler＇s reagent ammonia was detected in the slurry where the aggregated GAP particles were suspended in water and bubbled by pure nitrogen. Dependence of the concentration of ammonia upon bubbring time, velocity of the flow of nitrogen, and dosage of GAP particles was investigated. In comparison with the original GAP nanoparticles, the Raman scattering of the GAP particles undergoing the process of nitrogen fixation reveals that two sharp lines at 138 and 182 cm^-1, respectively, emerged from the broad continuum around 100-200 cm^-1. These two lines might be assigned to the translational motions of ammonia adsorbed on the surface of the GAP particles. An assessment of the infrared spectra of the two GAP particles led to the conclusion that the environment of the two H2O molecules was not identical. Analysis of the electron spin resonance results showed that the structure defect, gallium self-interstitial, was not involved in the nitrogen fixation of the GAP nanoparticles.     

金属硫(磷)化物用于电化学析氢反应

电化学分解水(Water Splitting)是获得高纯度氢能的重要手段。 因此,开发具有高活性低成本的电化学析氢反应(Hydrogen Evolution Reaction,HER)催化剂成为目前能源环境的研究热点之一。 本文总结了常用于HER反应的过渡金属硫化物以及磷化物非贵金属催化剂材料的合成方法,并且概况了如何构建特殊结构的金属硫化物及磷化物材料以调高材料的HER催化反应性能的方法,为开发其它高活性的非贵金属催化剂提供依据。     

High-Density and Thermally Stable Palladium Single-Atom Catalysts for Chemoselective Hydrogenations

Single-atom catalysts (SACs) have shown superior activity and/or selectivity for many energy- and environment-related reactions, but their stability at high site density and under reducing atmosphere remains unresolved. Herein, we elucidate the intrinsic driving force of a Pd single atom with high site density (up to 5 wt %) under reducing atmosphere, and its unique catalytic performance for hydrogenation reactions. In situ experiments and calculations reveal that Pd atoms tend to migrate into the surface vacancy-enriched MoC surface during the carburization process by transferring oxide crystals to carbide crystals, leading to the surface enrichment of atomic Pd instead of formation of particles. The Pd₁/α-MoC catalyst exhibits high activity and excellent selectivity for liquid-phase hydrogenation of substituted nitroaromatics (>99 %) and gas-phase hydrogenation of CO₂ to CO (>98 %). The Pd₁/α-MoC catalyst could endure up to 400 °C without any observable aggregation of single atoms.     

A Supported Palladium on Gallium-based Liquid Metal Catalyst for Enhanced Oxygen Reduction Reaction

Developing high-performance catalysts for oxygen reduction reaction to replace costly platinum-based materials is of great importance but still confronted with challenges. Herein, a kind of supported palladium liquid metal catalyst, which is prepared by galvanic replacement, surpasses commercial Pt/C and Pd/C in oxygen reduction catalysis with a higher half-wave potential of 0.92 V, mass activity of 1.85 A/mg_Pd at 0.90 V, and superior durability. The liquid metal support can both optimize the electronic structures of Pd sites and guarantee the dispersion of Pd atoms, which explains the enhanced activity and durability, respectively. This work opens an avenue for rational design of catalysts.     

Highly Active Electrocatalysis of the Hydrogen Evolution Reaction by Cobalt Phosphide Nanoparticles

Nanoparticles of cobalt phosphide, CoP, have been prepared and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) under strongly acidic conditions (0.50 M H₂SO₄, pH 0.3). Uniform, multi‐faceted CoP nanoparticles were synthesized by reacting Co nanoparticles with trioctylphosphine. Electrodes comprised of CoP nanoparticles on a Ti support (2 mg cm^?2 mass loading) produced a cathodic current density of 20 mA cm^?2 at an overpotential of ?85 mV. The CoP/Ti electrodes were stable over 24 h of sustained hydrogen production in 0.50 M H₂SO₄. The activity was essentially unchanged after 400 cyclic voltammetric sweeps, suggesting long‐term viability under operating conditions. CoP is therefore amongst the most active, acid‐stable, earth‐abundant HER electrocatalysts reported to date.     

Effect of Reduction Temperature on Hydrofining Performance of Supported Molybdenum Phosphide Catalyst

A series of supported molybdenum phosphide catalysts were prepared by impregnation method. XRD, TG-DTG, XPS and BET were used to study the phase, compositions and surface areas of the prepared catalysts. A model reactant containing thiophene, pyridine and cyclohexene was used for the measurements of catalytic activities. The effect of reduction temperature on catalytic activities was investigated. The analysis results by XRD and BET are very different when the reduction temperature is changed from 400 to 900 ℃. MoP/γ-Al2O3 catalysts and CoMoP/γ-Al2O3 catalysts prepared at the reduction temperature of 500 ℃ are the most active ones.     

Carrier-Induced Modification of Palladium Nanoparticles on Porous Boron Nitride for Alkyne Semi-Hydrogenation

Chemical modifiers enhance the efficiency of metal catalysts in numerous applications, but their introduction often involves toxic or expensive precursors and complicates the synthesis. Here, we show that a porous boron nitride carrier can directly modify supported palladium nanoparticles, originating unparalleled performance in the continuous semi-hydrogenation of alkynes. Analysis of the impact of various structural parameters reveals that using a defective high surface area boron nitride and ensuring a palladium particle size of 4–5 nm is critical for maximizing the specific rate. The combined experimental and theoretical analyses point towards boron incorporation from defects in the support to the palladium subsurface, creating the desired isolated ensembles determining the selectivity. This practical approach highlights the unexplored potential of using tailored carriers for catalyst design.     

过渡金属磷化物的制备及电催化析氢性能提升策略

氢能是一种绿色、 高效的二次能源, 在廉价的非贵金属催化剂的辅助下, 电解水制氢以其低成本和高效率受到广泛关注. 过渡金属磷化物因其独特近似球形三角棱柱单元结构能够暴露出更多配位不饱和表面原子, 因此在电解水制氢中表现出优异的催化活性和强耐腐蚀性. 本文综述了过渡金属磷化物的制备方法和在电催化析氢中的应用和性能的改善策略. 最后讨论了过渡金属磷化物催化剂存在的一些亟待解决的问题, 并展望了其未来的发展方向.     

一种新型加氢精制磷化钨催化剂的研究

采用偏钨酸铵{(NH4)2W4O13·18H2O}与磷酸氢二铵{(NH4)2HPO4}溶解、蒸发、焙烧和程序升温还原的方法,制备了无负载WP催化剂.利用XRD和BET对合成样品进行表征,采用TG/DTA方法对催化剂前体的氢还原过程进行考察.以制备的磷化钨为活性组分,Al2O3为稀释剂,在空速为4h-1、氢油比为1000、反应压力为3.0MPa、不同反应温度的条件下,对吡啶加氢脱氮、噻吩加氢脱硫和模型化合物为二苯并噻吩(含3000ppm硫)、喹啉(含2000ppm磷)和环己烷(溶剂)加氢脱硫(HDS)和加氢脱氮(HDN)反应活性进行测定,结果表明:无负载WP催化剂有相当的活性,其对大分子脱氮、脱硫活性明显优于对小分子脱氮、脱硫活性.     

氢还原重量法测定氯化钯产品中的钯含量

建立了氢还原重量法测定氯化钯产品钯含量的新方法,系统研究了测定条件,结合ICP-AES法考察了杂质元素对了分析结果的误差影响。结果表明：含钯量约3 g的氯化钯于750 ℃氢还原为海绵钯和105 ℃干燥水气的条件下,测定59.78%、59.98%和60.03%的钯含量,极差、标准偏差(S)、相对标准偏差(RSD,n=22)和重复性限(r)分别为±0.01%、0.0047%～0.0050%、0.0079%～0.0083%和0.009%～0.014%。样品加标准回收率99.98%。本法结果准确、精密,且与GB/T 15072.4-2008标准分析方法的吻合。     

酰胺羰基化反应中可重复使用的Pd/HZSM-5催化剂

 合成了非均相Pd/HZSM-5催化剂并将其用于酰胺羰基化反应. 结果表明,文献报道的Pd/C催化剂重复使用时其活性降为原来的一半,而Pd/HZSM-5催化剂重复使用4次后活性基本不变. 反应前后两种催化剂的TEM电镜照片表明, Pd/C上的金属钯粒子在反应后团聚并形成网络状结构,而Pd/HZSM-5上钯粒子在反应后仍保持与反应前相同的均匀分布状态.     

Rapid Room‐Temperature,Chemoselective C −C Coupling of Poly(pseudo)halogenated Arenes Enabled by Palladium(I) Catalysis in Air

While chemoselectivities in Pd⁰‐catalyzed coupling reactions are frequently non‐intuitive and a result of a complex interplay of ligand/catalyst, substrate, and reaction conditions, we herein report a general method based on Pd^I that allows for an a priori predictable chemoselective C −C coupling at C−Br in preference to C−OTf and C−Cl bonds, regardless of the electronic or steric bias of the substrate. The C−C bond formations are extremely rapid (<5 min at RT) and are catalyzed by an air‐ and moisture‐stable Pd^I dimer under open‐flask conditions.     

氢还原重量法测定氯化钯产品中的钯

系统研究了氢还原重量法测定氯化钯产品中钯含量的测定条件,考察了杂质元素对钯分析结果的误差影响。结果表明:于选定条件下,测定59.78%~60.03%含量的钯,极差、标准偏差(SD)、相对标准偏差(RSD,n=22)和重复性限(r)分别为±0.01%,0.0047%~0.0050%,0.0079%~0.0083%和0.009%~0.014%,样品加标回收率达到99.98%,钯分析结果准确、可靠、精密度高。     

硅胶负载钯: 一种新型有效而可循环的Heck反应的催化剂

本文报道了一种新型硅胶负载钯催化剂在Heck 反应中的应用。在硅胶负载钯催化剂,碳酸钾为碱,DMF为溶剂的反应条件下（无膦和无游离胺的存在）,碘代芳烃、溴代芳烃和活泼的氯代芳烃与烯烃发生偶联反应生成高产率相应的偶联产物。而且硅胶负载的钯催化剂经简单处理,可循环使用6次不降低活性。     

Prussian Blue‐Derived Iron Phosphide Nanoparticles in a Porous Graphene Aerogel as Efficient Electrocatalyst for Hydrogen Evolution Reaction

Tailoring of new hydrogen evolution reaction (HER) electrocatalyst with earth abundant elements is important for large scale water splitting and hydrogen production. In this work, we present a simple synthetic method for incorporating iron phosphide (FeP) particles into three‐dimensional (3D) porous graphene aerogel (GA) structure. The FeP formed in porous 3D GA (FeP/GA) is derived from electroactive Fe hexacyanoferrate (FeHCF). The advantage of incorporating FeP, in the porous 3D graphene network enables high accessibility for HER. As synthesized FeP/GA catalyst shows good electrocatalytic activity for HER in both acidic and alkaline solutions. The developed method can be useful for synthesizing metal hexacyanoferrate derived mono/bimetal phosphide catalyst in porous 3D graphene aerogels.     

功能化碳纳米管表面高分散的钯纳米粒子在碱性溶液中的甲醇氧化行为

本工作中在水溶液体系中以芳烃重氮盐修饰的多壁碳纳米管(MWNT)为载体构筑了钯(Pd)纳米粒子碳纳米管复合结构。以MWNT的侧壁上C-C共价键接的氨基苯甲酸为沉积活化中心,制备了高分散高催化活性的钯(Pd)纳米粒子。结构成分和形貌分别用XRD和TEM表征。循环伏安(CV) 和交流阻抗的研究表明上述复合结构在碱性溶液中对甲醇的电催化氧化有很高的活性及稳定性。芳烃重氮盐修饰的MWNT是一种非常好的催化剂载体,而Pd-MWNT复合材料在燃料电池有着广泛的应用前景。     

磁性纳米粒子负载钯催化有机合成反应研究进展

磁性纳米粒子负载钯催化的有机合成反应,由于具有催化活性高,催化剂在外加磁场作用下即可快速分离和重复使用等特点,已引起了人们的广泛关注.综述了近年来磁性纳米粒子负载钯催化有机合成反应的研究进展,载体包括Fe3O4纳米粒子、有机小分子修饰的磁性纳米粒子、SiO2包覆的磁性纳米粒子、碳修饰磁性纳米粒子、羟基磷灰石包覆的磁性纳米粒子和有机高分子修饰的磁性纳米粒子等.     

磁性纳米颗粒负载钯催化剂对Heck反应的催化活性

采用水热法合成了碳包埋磁性纳米复合颗粒C/(Au@Fe),并以之为载体制备了纳米钯催化剂,利用透射电镜、X射线光电子能谱和振动样品磁强计等手段对催化剂进行了表征,评价了催化剂对Heck反应的催化活性.结果表明,催化剂的平均粒径约为300nm,表面覆盖着一层粒径为12nm的钯颗粒,整个催化剂呈现超顺磁性.对于碘代苯与丙烯酸之间的Heck反应,在乙酸钠或三乙胺碱性条件下反应4h,碘代苯转化率可达95%以上.催化剂重复使用10次时仍可保持很高的催化活性(碘代苯转化率88%).对于其他不同反应底物之间的Heck反应,催化剂同样显示有较高的催化活性.催化剂可稳定分散于反应体系中,并可在外磁场作用下快速与反应体系分离.