Combinatorial screening of ternary Pt–Ni–Cr catalysts for methanol electro-oxidation

Methanol electro-oxidation activity of ternary Pt–Ni–Cr system was studied by using a combinatorial screening method. A Pt–Ni–Cr thin-film library was prepared by sputtering and quickly characterized by a multichannel multielectrode analyzer. Among the 63 different composition thin-film catalysts, Pt₂₈Ni₃₆Cr₃₆ showed the highest methanol electro-oxidation activity and good stability. This new composition was also studied in its powder form by synthesizing and characterizing Pt₂₈Ni₃₆Cr₃₆/C catalyst. In chronoamperometry testing, the Pt₂₈Ni₃₆Cr₃₆/C catalyst exhibited “decay-free” behavior during 600 s operation by keeping its current density up to 97.1% of its peak current density, while the current densities of Pt/C and Pt₅₀Ru₅₀/C catalysts decreased to 14.0% and 60.3% of their peak current densities, respectively. At 600 s operation, current density of the Pt₂₈Ni₃₆Cr₃₆/C catalyst was 23.8 A g_{noble metal}⁻¹, while that of those of the Pt/C and Pt₅₀Ru₅₀/C catalysts were 2.74 and 18.8 A g_{noble metal}⁻¹, respectively.     

One-step synthesis of porous PtNiCu trimetallic nanoalloy with enhanced electrocatalytic performance toward methanol oxidation

Pt-based alloy nanoporous structures have attracted a lot of attention because of their high activity and stability toward alcohol oxidation reactions. Especially, Pt alloying with Earth-abundant metal can lower the cost of catalyst. Here, we introduce a one-pot approach to synthesize bimetallic PtCu and Ni-doped PtCu nanoalloy with porous structure. The as-synthesized Ni-doped Pt₆₀Ni₃Cu₃₇ nanoalloys exhibit excellent electrocatalytic properties toward methanol oxidation in acidic medium. The mass activity of the as-synthesized Pt₆₀Ni₃Cu₃₇ nanoalloys is 3.6 times and 5.3 times that of Pt₅₅Cu₄₅ nanoalloys and commercial Pt black for methanol oxidation in 0.2?M methanol solution. Besides, the stability of the as-synthesized Pt₆₀Ni₃Cu₃₇ nanoalloys was much better than Pt₅₅Cu₄₅ nanoalloys and commercial Pt black. After 3600?s chronoamperometry test, the remaining values of the Pt₆₀Ni₃Cu₃₇ nanoalloys are 3.7 times and 11.0 times that of Pt₅₅Cu₄₅ nanoalloys and commercial Pt black. And it is the first time to report that small amount of Ni dopants can boost the activity and stability of PtNiCu alloys toward methanol oxidation.     

Relating the Composition of PtxRu100−x/C Nanoparticles to Their Structural Aspects and Electrocatalytic Activities in the Methanol Oxidation Reaction

A controlled composition‐based method—that is, the microwave‐assisted ethylene glycol (MEG) method—was successfully developed to prepare bimetallic Pt_xRu_100?x/C nanoparticles (NPs) with different alloy compositions. This study highlights the impact of the variation in alloy composition of Pt_xRu_100?x/C NPs on their alloying extent (structure) and subsequently their catalytic activity towards the methanol oxidation reaction (MOR). The alloying extent of these Pt_xRu_100?x/C NPs has a strong influence on their Pt d‐band vacancy and Pt electroactive surface area (Pt ECSA); this relationship was systematically evaluated by using X‐ray absorption (XAS), scanning electron microscopy (SEM) coupled with energy dispersive X‐ray spectroscopy (EDX), transmission electron microscopy (TEM), density functional theory (DFT) calculations, and electrochemical analyses. The MOR activity depends on two effects that act in cooperation, namely, the number of active Pt sites and their activity. Here the number of active Pt sites is associated with the Pt ECSA value, whereas the Pt‐site activity is associated with the alloying extent and Pt d‐band vacancy (electronic) effects. Among the Pt_xRu_100?x/C NPs with various Pt:Ru atomic ratios (x=25, 50, and 75), the Pt₇₅Ru₂₅/C NPs were shown to be superior in MOR activity on account of their favorable alloying extent, Pt d‐band vacancy, and Pt ECSA. This short study brings new insight into probing the synergistic effect on the surface reactivity of the Pt_xRu_100?x/C NPs, and possibly other bimetallic Pt‐based alloy NPs.     

The determination of platinum-group elements (PGE) by nickel sulfide fire-assay: Coexisting PGE-phases in the nickel sulfide button

The chemical composition of phases in buttons obtained by nickel sulfide fire-assay during the determination of platinum-group elements (PGE) has been investigated by electron microprobe analysis. Different PGE-containing phases, due to varying flux constituents and species of added PGE, have been detected. By using sodium tetraborate as flux constituent and adding PGE as chlorides, in a cryptocrystalline Ni₃S₂ matrix with low PGE (mainly Rh and Ru) contents, Rh- and Ru-bearing nickel sulfides ((Ni_7.68–7.80Ru_0.84–0.90Rh_0.35–0.43)₉S₈) and Ir alloys ((Ir,Pt,Os)_0.56–0.62(Ru,Rh)_0.25–0.28Ni_0.12–0.19) are found. Treatment with lithium tetraborate leads to a Ni₃S₂ matrix exhibiting slightly higher Rh and Ru contents, with inclusions of nickel-rhodium sulfides (Ni₈Rh₄S₉) and platinumnickel alloys (Pt_0.45Ni_0.36–0.39Ru_0.11–0.14Rh_0.05). Finely dispersed metallic colloidals from an automobile catalyst, with platinum and rhodium as main components, have given only platinum-nickel alloys (Pt_1–xNi_x). Considerable losses of PGE during analytical steps following the fire assay are expected when their contents in sulfidic phases, which are more likely to be dissolved, are high.     

Decorating Pt/C Nanoparticles with Ru by Wall‐Jet Configuration: The Role of Coverage Degree on the Catalyst Activity for Glycerol Electrooxidation

Here, we built Ru‐decorated Pt/C nanoparticles with different coverage degrees (θ_Ru) by wall‐jet configuration for the first time, and we investigated their catalytic properties towards glycerol electrooxidation in acidic medium. Moreover, we used the most active catalysts as the anode in electrolysis to produce carbonyl compounds. The use of an electrochemical cell in wall‐jet configuration allows for the controlling of electrodeposition through easily handling parameters; namely, the θ_Ru is controlled by changing the concentration of the metallic precursor, speed, and volume of injection onto a Pt/C‐modified glassy carbon electrode under applied potential. Excess of Ru on a Pt surface inhibits glycerol dissociative adsorption, which limits further electrooxidation; whereas low θ_Ru do not provide surface oxygen species to the anodic reaction. Hence, intermediates θ_Ru reveal active catalysts – namely, θ_Ru=0.42 shifts the onset potential 170 mV towards lower values and increases 1.65‐fold the current density at 0.5 V. The stability of this catalyst is also enhanced by maintaining a more constant current density during successive potential cycles in the presence of glycerol and by avoiding Ru leaching from the surface. The electrolysis on Ru‐decorated Pt/C is shown to lead the reaction towards formic acid (‘high oxidation state’), decreasing the amounts of glyceradehyde, glycolic acid, and dihydroxyacetone, as a result of the improved catalytic properties.     

多元醇法合成的Pt2.6Sn1Ru0.4/C用作直接乙醇燃料电池高性能阳极催化剂

采用多元醇法制备了不同原子比例和载量的PtSnRu/C催化剂,利用透射电镜和X射线光电子能谱表征了所制备催化剂的物化性能,采用直接乙醇燃料电池（DEFC）单池性能测试了其电化学性能,并利用电化学原位光谱、气相色谱和中和滴定分析了乙醇电氧化过程和产物. DEFC单电池测试表明Pt_2.6Sn₁Ru_0.4/C催化剂具有较高的电池性能,其中,以60 wt% Pt_2.6Sn₁Ru_0.4/C催化剂为阳极的DEFC性能最高,90 ℃下最高功率密度为121 mW/cm². 电化学原位红外光谱和阳极产物分析表明乙酸、乙醛、乙酸乙酯和CO₂是乙醇电化学氧化产物,Pt_2.6Sn₁Ru_0.4/C催化剂上乙醇的氧化效率较高. 阳极乙醇氧化活化能和催化剂表面组成分析结果表明,表面组成的相互作用使Pt_2.6Sn₁Ru_0.4/C催化剂具有较低的乙醇氧化活化能和较高的乙醇氧化活性.     

Nanoporous PtRu Alloys with Unique Catalytic Activity toward Hydrolytic Dehydrogenation of Ammonia Borane

Nanoporous (NP) PtRu alloys with three different bimetallic components were straightforwardly fabricated by dealloying PtRuAl ternary alloys in hydrochloric acid. Selective etching of aluminum from source alloys generates bicontinuous network nanostructures with uniform size and structure. The as‐made NP‐PtRu alloys exhibit superior catalytic activity toward the hydrolytic dehydrogenation of ammonia borane (AB) than pure NP‐Pt and NP‐Ru owing to alloying platinum with ruthenium. The NP‐Pt₇₀Ru₃₀ alloy exhibits much higher specific activity toward hydrolytic dehydrogenation of AB than NP‐Pt₃₀Ru₇₀ and NP‐Pt₅₀Ru₅₀. The hydrolysis activation energy of NP‐Pt₇₀Ru₃₀ was estimated to be about 38.9 kJ mol^?1, which was lower than most of the reported activation energy values in the literature. In addition, recycling tests show that the NP‐Pt₇₀Ru₃₀ is still highly active in the hydrolysis of AB even after five runs, which indicates that NP‐PtRu alloy accompanied by the network nanoarchitecture is beneficial to improve structural stability toward the dehydrogenation of AB.     

Synthesis of Ni–Ru Alloy Nanoparticles and Their High Catalytic Activity in Dehydrogenation of Ammonia Borane

We report the synthesis and characterization of new Ni_xRu_1?x (x=0.56–0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet‐chemistry method using a rapid lithium triethylborohydride reduction of Ni²⁺ and Ru³⁺ precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X‐ray spectroscopy (EDX), and X‐ray photoelectron spectroscopy (XPS). We found that the as‐prepared Ni–Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni–Ru alloy NPs, and in particular the Ni_0.74Ru_0.26 sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core‐shell NPs. The hydrolysis activation energy for the Ni_0.74Ru_0.26 alloy catalyst was measured to be approximately 37 kJ mol^?1. This value is considerably lower than the values measured for monometallic Ni (≈70 kJ mol^?1) and Ru NPs (≈49 kJ mol^?1), and for Ni@Ru (≈44 kJ mol^?1), and is also lower than the values of most noble‐metal‐containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal.     

Ternary CoPtAu Nanoparticles as a General Catalyst for Highly Efficient Electro‐oxidation of Liquid Fuels

Efficient electro‐oxidation of formic acid, methanol, and ethanol is challenging owing to the multiple chemical reaction steps required to accomplish full oxidation to CO₂. Herein, a ternary CoPtAu nanoparticle catalyst system is reported in which Co and Pt form an intermetallic L1₀‐structure and Au segregates on the surface to alloy with Pt. The L1₀‐structure stabilizes Co and significantly enhances the catalysis of the PtAu surface towards electro‐oxidation of ethanol, methanol, and formic acid, with mass activities of 1.55 A/mg_Pt, 1.49 A/mg_Pt, and 11.97 A/mg_Pt, respectively in 0.1 m HClO₄. The L1₀‐CoPtAu catalyst is also stable, with negligible degradation in mass activities and no obvious Co/Pt/Au composition changes after 10 000 potential cycles. The in situ surface‐enhanced infrared absorption spectroscopy study indicates that the ternary catalyst activates the C?C bond more efficiently for ethanol oxidation.     

Methanol oxidation on unsupported and carbon supported Pt + Ru anodes

A novel Pt + Ru electrode material is shown to be highly active for the direct electro-oxidation of methanol in H₂SO₄ solutions and to show very little tendency to poison. X-ray photoelectron spectroscopy of this material before use as an anode showed that the ruthenium is oxidised and that there is an important surface concentration of oxidised platinum. After prolonged use as a methanol-oxidation anode, the concentration of oxidised platinum is somewhat increased and there is no evidence for any Pt-CO or Pt₂ = CO species; rather adsorbed formate is present. These data are consistent with Ru acting as a promoter of active surface oxygen. Dispersion of the Pt and Ru on a pure carbon support gives a much greater performance per gram of precious metal; however, the initial increase in overpotential is greater by over 100 mV. The differences in the catalytic behaviour of these two materials is discussed, and the importance of competing reactions is considered.     

Effect of Ru addition on the structural characteristics and the electrochemical activity for ethanol oxidation of carbon supported Pt–Sn alloy catalysts

Binary Pt–Sn/C (1:1) and ternary Pt–Sn–Ru/C (1:1:0.3 and 1:1:1) catalysts were synthesized by reduction of precursors with formic acid, and their activity for ethanol oxidation was compared with that of commercial Pt/C and Pt–Ru/C catalysts. Linear sweep voltammetry measurements at 40 and 90 °C showed that for potentials higher than 0.3 V vs. RHE, the Pt–Sn–Ru/C (1:1:0.3) catalyst presents the highest activity for ethanol electro-oxidation, while the electrochemical activity of the Pt–Sn–Ru/C (1:1:1) catalyst was lower than that of both the binary Pt–Sn/C and Pt–Ru/C catalysts. Tests in a single direct ethanol fuel cell confirmed the superior performance of the Pt–Sn–Ru/C (1:1:0.3) electrocatalyst. The positive effect of the Ru presence in the Pt–Sn–Ru/C (1:1:0.3) catalyst was ascribed to the interactions between Sn and Ru oxides.     

Ultrafine PtRu Dilute Alloy Nanodendrites for Enhanced Electrocatalytic Methanol Oxidation

Dilute alloy nanostructures have been demonstrated to possess distinct catalytic properties. Noble-metal-induced reduction is one effective synthesis strategy to construct dilute alloys and modify the catalytic performance of the host metal. Herein, we report the synthesis of ultrafine PtRu dilute alloy nanodendrites (PtRu NDs, molar ratio Ru/Pt is 1:199) by the reduction of Ru^III ions induced by Pt metal. For the methanol oxidation reaction, PtRu NDs showed the highest forward peak current density (2.66 mA cm⁻², 1.14 A/mg_Pt) and the best stability compared to those of pure-Pt nanodendrites (pure-Pt NDs), commercial PtRu/C and commercial Pt/C catalysts.     

Bimetallic Cluster Provides a Higher Activity Electrocatalyst for Methanol Oxidation

The cluster complex Pt₂Ru₄(CO)₁₈ was used as a precursor to prepare a 60 wt% 1:2 Pt:Ru nanoparticles on carbon (PtRu/C) for use as an electrocatalyst for methanol oxidation. This bimetallic carbonyl cluster complex was found to provide smaller, more uniform bimetallic nanoparticle that exhibited higher electrocatalytic activity than a 60 wt% 1:1 Pt:Ru commercial catalyst from E-Tek. Using bimetallic cluster precursors simplifies the synthetic procedures by reducing the need for high temperature reduction and assures a more intimate mixing of the two different metals. Transmission electron microscopy (TEM) images of the catalyst obtained from the cluster precursor showed bimetallic nanoparticles having a narrow size range of 2–3 nm that were dispersed uniformly over the surface of the support. Images of the commercial catalyst showed particles 3–4 nm in diameter that tended to agglomerate near the edges of the carbon support particles. Cyclic voltammograms of methanol oxidation from the two catalysts showed significantly higher activity for the cluster-derived catalyst. The onset potential for methanol oxidation for the cluster-derived catalyst was approximately 170 mV lower than that of the commercial catalyst at 100 A/g Pt, and approximately 250 mV lower at 400 A/g Pt. ^* This report is dedicated to Prof. Günter Schmid on the occasion of his 70th birthday.     

Exploration of electrodeposited platinum alloy catalysts for methanol electro-oxidation in 0.5 M H<Subscript>2</Subscript>SO<Subscript>4</Subscript>: Pt-Ni system

In this work, we examine the electrocatalytic activity of electrodeposited Platinum (Pt)-Nickel (Ni) alloy layers on an inert substrate electrode for methanol oxidation reaction. Analyses using energy-dispersive fluorescent X-ray analysis and powder X-ray diffractometry confirm alloying of Pt with Ni in a range of compositions. Steady-state polarisation measurements in 0.5 M methanol+0.5 M H₂SO₄ solutions clearly show that the onset of electro-oxidation shifts to less anodic potential values (approximately 160 mV), while also exhibiting current enhancements up to ~15 times the currents obtained for the pure Pt electrodeposit. A linear relationship between the cyclic voltammetric peak (oxidation) current and [MeOH] is observed at a scan rate of 50 mVs^–1, thus indicating reduced influence of adsorbed CO (CO_ads) surface poison. A critical composition, Pt (92%)/Ni (8%) [denoted Pt-Ni(3) alloy] is found to exhibit maximum electrocatalytic activity, beyond which the activity drops, whereas pure Ni does not catalyse the reaction. While the promotion of electro-oxidation is understood to be largely due to the alloy catalyst, surface redox species of Ni oxide formed during the electro-oxidation process may also contribute to the oxygenation of CO_ads, thereby enhancing the oxidation current. Plausible mechanisms of methanol oxidation on Pt/ transition metal alloy electrocatalysts are discussed in terms of electron transfer (in the alloy) and the role of Ni oxide species.     

Complexing behaviour of aromatic thioamides (ArCSNHCOR). Transition metal complexes of N-carboethoxy-4-chlorobenzene- and N-carboethoxy-4-bromobenzene thioamide ligands

N-Carboethoxy-4-chlorobenzene thioamide (Hcct or HL) and N-carboethoxy-4-bromobenzene thioamide (Hcbt or HL) react with bivalent (Ni, Co, Cu, Ru, Pd and Pt), trivalent (Ru and Rh) and tetravalent (Pt) transition metal ions to give [M^II(L)₂], [Ru^III(L)₃], [Rh^III(L)(HL)Cl₂] and [Pt(L)₂Cl₂] complexes, respectively. In the presence of pyridine, Co^II and Ni^II salts react with the ligands (HL) to give [M^II(L)₂Py] (M = Co and Ni) complexes. Soft metal ions abstract sulphur from the ligands to yield the corresponding sulphide, together with oxygenated forms of the ligands. All the metal complexes have been characterised by chemical analyses, conductivity, spectroscopic and magnetic measurements.     

Nanostructured catalysts for direct electrooxidation of dimethyl ether based on Bi- and trimetallic Pt–Ru and Pt–Ru–Pd alloys prepared from coordination compounds

Bi- and trimetallic platinum–ruthenium and platinum–ruthenium–palladium catalysts with specified atomic ratios Pt: Ru = 1: 1 and Pt: Ru: Pd = 1: 1: 0.1, respectively, were synthesized from the coordination compounds of the metals deposited on highly dispersed carbon black. The catalysts were characterized by powder X-ray diffraction, electron dispersive analysis, and transmission electron microscopy. According to voltammetry data, the highest activity in the dimethyl ether (DME) electrooxidation is exhibited by the catalyst Pt_0.43Ru_0.47Pd_0.1/C; hence, it may be considered as a promising anode material for direct DME fuel cells.     

Effects of thermal activation on the oxidation pathways of methanol at bulk Pt–Ru alloy electrodes

The competition between pathways that lead to adsorbed CO and CO₂ during the electrochemical oxidation of 1.0 M methanol in 0.1 M HClO₄ on two bulk Pt–Ru alloys (10 at.% Ru (X_Ru≈0.1) and 90 at.% Ru (X_Ru≈0.9)) was investigated for temperatures in the range of 25–80°C. On the high Ru content alloy studied (X_Ru≈0.9), the dissociative chemisorption of methanol was inhibited below 70°C; the faradaic current for methanol oxidation was low, and only small quantities of adsorbed CO and CO₂ were detected with infrared spectroscopy between 0.2–0.8 V (vs. RHE). At 80°C, strong infrared bands from CO₂ and adsorbed, atop coordinated CO were observed over the potential ranges of 0.4–0.8 V and 0.2–0.8 V, respectively. The infrared measurements are consistent with the observation that bulk, high Ru content alloy electrodes appear passivated toward methanol oxidation below 70°C. On the low Ru content alloy studied (X_Ru≈0.1), the methanol surface chemistry was similar to that of pure, polycrystalline Pt, but the electrode was more poison resistant than Pt. For both alloys, the persistence of strong adsorbed CO bands and rapid CO₂ production between 0.4–0.8 V suggests CO functions as a reactive species with high steady-state coverages at these potentials.     

The formation of Pt-Ru alloy nanoparticles in a carbon matrix under IR pyrolysis conditions

Nanosized Pt-Ru alloy and Pt₁₃Ru₂₇ intermetallic compound particles dispersed in a carbon matrix were obtained for the first time directly during the preparation of the composite. The alloying of the Pt and Ru particles occurred at IR pyrolysis intensities corresponding to temperatures above 700°C over the whole homogeneity range of solid solutions based on platinum. Metallic nanoparticles were round-shaped (the mean size 6–8 nm) and had a narrow particle-size distribution.     

Pt-Se纳米空球修饰玻碳电极上甲酸的电催化氧化

以无定形硒溶胶为模板制备了不同硒覆盖度(θSe)(θSe=0.49,0.39,0.06,0)的Pt-Se和Pt纳米空球(分别记为(Pt-Se)HN和PtHN),发展了利用亚硫酸盐彻底除去核壳纳米粒子上Se的方法.对获得的纳米空球进行了形貌和结构的表征,结果表明所制备的(Pt-Se)HN粒径均匀,分散性好,球壳呈多孔结构.以其作为电催化剂制备了(Pt-Se)HN修饰的玻碳(GC)电极((Pt-Se)HN/GC),利用常规电化学方法比较该电极与PtHN/GC和商用碳载铂(Pt/C)修饰GC(Pt/C/GC)电极对甲酸的催化氧化作用,发现对甲酸氧化的活性顺序为(Pt-Se)HN/GCPtHN/GCPt/C/GC.三种电极催化甲酸氧化的机理有所不同:前者更倾向于通过弱吸附中间体直接氧化成CO2的单途径机理进行,后两者则通过强吸附和弱吸附中间体的双途径机理进行.在一定Se覆盖度条件下,(Pt-Se)HN/GC对甲酸的氧化有助催化作用.     

Bimetallic RuM (M=Co,Ni) Alloy NPs Supported on MIL-110(Al): Synergetic Catalysis in Hydrolytic Dehydrogenation of Ammonia Borane

By adjusting various Ru/M (M=Co, Ni) molar ratios, a series of highly dispersed bimetallic RuM alloy nanoparticles (NPs) anchored on MIL-110(Al) have been successfully prepared via a conventional impregnation-reduction method. And they are first used as heterogeneous catalysts for the dehydrogenation reaction of AB at room temperature. The results reveal that the as-prepared Ru₁Co₁@MIL-110 and Ru₁Ni₁@MIL-110 exhibit the highest catalytic activities in different RuCo and RuNi molar ratios, respectively. It is worthy of note that the turnover frequency (TOF) values of Ru₁Co₁@MIL-110 and Ru₁Ni₁@MIL-110 catalysts reached 488.1 and 417.1 mol H₂ min^-1 (mol Ru)^-1 and the activation energies (E_a) are 31.7 and 36.0 kJ/mol, respectively. The superior catalytic performance is attributed to the bimetallic synergistic action between Ru and M, uniform distribution of metal NPs as well as bi-functional effect between RuM alloy NPs and MIL-110. Moreover, these catalysts exhibit favorable stability after 5 consecutive cycles for the hydrolysis of AB.