Employing iron and nickel to enhance ethanol oxidation of Pd-based anodes in alkaline medium

Enhancing the Catalytic Activity of Pd Nanocatalysts for Anion Exchange Membrane Direct Ethanol Fuel Cells by Functionalizing Vulcan XC-72 with Cu Organometallic Compounds

The most widely used support in low-temperature fuel cell applications is the commercially available Vulcan XC-72. Herein, we report its functionalization with the home-obtained mesityl copper (Cu-mes) and Cu coordinate (Cu(dmpz)L2) organometallic compounds. Pd nanoparticles are anchored on the supports obtaining Pd/CCu-mes, Pd/CCu(dmpz)L2, and Pd/C (on nonfunctionalized support). The polarization curves of the ethanol oxidation reaction (EOR) show that Pd/CCu-mes and Pd/CCu(dmpz)L2 promote the reaction at a more negative onset potential, i.e., E onset = 0.38 V/reversible hydrogen electrode (RHE), compared to 0.41 V/RHE of Pd/C. The mass current density (j m) delivered by Pd/CCu-mes is considerably higher (1231.3 mA mgPd -1), followed by Pd/CCu(dmpz)L2 (1001.8 mA mgPd -1), and Pd/C (808.3 mA mgPd -1). The enhanced performance of Pd/CCu-mes and Pd/CCu(dmpz)L2 for the EOR (and tolerance to CO poisoning) is attributed to a shift of their d-band center toward more negative values, compared to Pd/C, because of the formation of PdCu alloyed phases arising from the functionalization. In addition, laboratory-scale tests of the anion exchange membrane-direct ethanol fuel cell assembled with Pd/CCu-mes show the highest open circuit voltage (OCV = 0.60 V) and cell power density (P cell = 0.14 mW cm-2). As a result of its high catalytic activity, Pd/CCu-mes can find application as an anode nanocatalyst in AEM-DEFCs.

Glycerol Electro-Oxidation in Alkaline Medium with Pt-Fe/C Electrocatalysts Synthesized by the Polyol Method: Increased Selectivity and Activity Provided by Less Expensive Catalysts

We have investigated platinum catalysts containing iron as a modifier to obtain catalysts with superior electrocatalytic activity toward glycerol electro-oxidation in an alkaline medium. The electrocatalysts, supported on carbon Vulcan, were synthesized by the polyol method. The physicochemical characterization data showed that the metals were well distributed on the carbon support and had small particle size (2 nm). The Pt:Fe metal ratio differed from the nominal composition, indicating that reducing iron with platinum was difficult, even though some parameters of the synthesis process were changed. Electrochemical analyses revealed that PtFe/C was more active and stable than commercial Pt/C was, and analysis of the electrolysis by-products showed that iron addition to Pt/C boosted the glycerol conversion and selectivity for glyceric acid formation.

Tuning Dimensions of Complexes through Selective In Situ Reaction, Mechanistic Insights into Ni(II)-Catalyzed Br-OH Exchange, Magnetic Properties, and Density Functional Theory Studies

Two coordination polymers (CPs), namely, [Mn₃(L)₂(4,4'-bipy)₂(H₂O)₂]_n (1) and [Ni(L₁)(1,4-bib)(H₂O)]_n (2) (H₃L = 5-(3-bromo-4-carboxyphenoxy)isophthalic acid, H₂L₁ = 5-(3-hydroxyphenoxy)isophthalic acid, 4,4'-bpy = 4,4'-bipyridine, and 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene), were synthesized under hydrothermal conditions. Most notably, with the help of the bromine atom-inducing effect, ligand transformation was observed in the structure of complex 2, which was scrutinized thoroughly by single crystal X-ray crystallography and X-ray photoelectron spectroscopy (XPS). Strikingly, Ni(II) ions were utilized as both coordinated atoms and as a catalyst for in situ Br-OH exchange of H₃L in the process, as a result of which the product would have preferred to form a one-dimensional chain. The same reaction cannot happen in 1, leading to form a two-dimensional structure. Moreover, Ni(II)-catalyzed and magnetic exchange mechanisms were well interpreted using density functional theory (DFT) calculations. Finally, complexes 1-2 show three-dimensional (3D) supramolecular structures because of intermolecular weak interactions (C-Br···π, C-H···π, C-H···O, and π···π stacking) and exhibit utterly different antiferrimagnetic coupling interactions.

Gold nanobipyramids doped with Au/Pd alloyed nanoclusters for high efficiency ethanol electrooxidation

Plasmonic metal nanostructures are of great interest due to their excellent physicochemical properties and promising applications in a wide range of technical fields. Among metal nanostructures, bimetallic nanostructures with desired morphologies, such as core-shell, uniform alloy and surface decoration, are of great interest due to their improved properties and superior synergetic effects. In this paper, Au/Pd nanoclusters were deposited on the surface of gold nanobipyramids (AuBPs) into a core-shell nanostructure (AuBP@Au x Pd1-x ) through a reductive co-precipitation method. The AuBP@Au x Pd1-x nanostructure integrates effectively the advantages of plasmonic AuBPs and catalytic Pd ultrafine nanoclusters, as well as the stable Au/Pd alloy shell. The AuBP@Au x Pd1-x nanostructure exhibits superior electrocatalytic activity and durability for oxygen reduction in alkaline media owing to the synergistic effect between the AuBP core and Au/Pd shell. Furthermore, the shell thickness of AuBP@Au x Pd1-x nanostructures can be adjusted by varying the amount of precursor. Overall, the catalytic activity of bimetallic Au/Pd catalysts is likely to be governed by a complex interplay of contributions from the particle size and shape.

Engineering One-Dimensional AuPd Nanospikes for Efficient Electrocatalytic Nitrogen Fixation

Designing one-dimensional (1D) bimetallic nanomaterials is of great significance for electrochemical nitrogen fixation. Inspired by this, 1D AuPd nanospikes (AuPd NSs) composed with internal Au nanowire and external Pd nanohumps were fabricated by a flexible low-temperature wet-chemical method. Benefiting from the excellent electron transport efficiency of the 1D material and the accessible surface area provided by the unique nanospike-like structure, AuPd NSs exhibit outstanding nitrogen reduction reaction performance with an NH₃ yield rate of 16.9 μg h^-1 mg^-1_cat. and a Faradaic efficiency of 15.9% at -0.3 V under 0.1 M Na₂SO₄. This work not only provides an effective electrocatalyst for nitrogen fixation technology, but also presents a flexible method for the controlled synthesis of spike-like nanomaterials.

Au Nanoparticles Modified with Pt, Ru and SnO2 as Electrocatalysts for Ethanol Oxidation Reaction in Acids

The anodic reaction in direct ethanol fuel cells (DEFCs), ethanol oxidation reaction (EOR) faces challenges, such as incomplete electrooxidation of ethanol and high cost of the most efficient electrocatalyst, Pt in acidic media at low temperature. In this study, core-shell electrocatalysts with an Au core and Pt-based shell (Au@Pt) are developed. The Au core size and Pt shell thickness play an important role in the EOR activity. The Au size of 2.8 nm and one layer of Pt provide the most optimized performance, having 6 times higher peak current density in contrast to commercial Pt/C. SnO₂ as a support also enhances the EOR activity of Au@Pt by 1.73 times. Further modifying the Pt shell with Ru atoms achieve the highest EOR current density that is 15 and 2.5 times of Pt/C and Au@Pt. Our results suggest the importance of surface modification in rational design of advanced electrocatalysts.

Surface engineering of ultrasmall supported PdxBi nanoalloys with enhanced electrocatalytic activity for selective alcohol oxidation

Ultrasmall and homogeneous bimetallic PdxBi nanoalloys are well distributed on a Vulcan carbon support by a facile, low-cost synthetic strategy. The electrochemical activity of the as-prepared homogeneous PdxBi nanoalloy/carbon black nanocomposites is closely related to the content of Bi, revealing their excellent electrocatalytic performance for selective oxidation of monohydric alcohols and vicinal diols in alkali medium.