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Although palladium (Pd) based materials are considered the best catalyst for formic acid oxidation reaction (FAOR), they are still confronted with a lot of barriers, such as the growth/sintering of Pd nanoparticles (NPs) and the accumulation of adsorbed poisoning intermediates. Herein, tin dioxide (SnO 2) decorated carbon black was utilized as the catalyst carrier to synthesize Pd/SnO 2 /C for FAOR. The introduction of SnO 2 significantly reduced the particle size of Pd NPs and forming the Pd–O–Sn structure. Compared with Pd/C, Pd/SnO 2 /C owned higher concentration of O ads and less adsorption amount of poisoning intermediates. The oxygen atoms adsorbed on Pd surface were rapidly transferred to SnO 2 due to the spillover effect. The FAOR reaction kinetic results showed that the introduction of SnO 2 accelerated the diffusion rate of formic acid on the electrode surface. Pd/SnO 2 /C exhibited high specific activity (5.97 mA cm−2), excellent durability, and high anti-CO poisoning ability toward FAOR due to the introduction of SnO 2. •The defects and holes of SnO 2 anchor Pd and promote the dispersion of Pd NPs. •Pd–O–Sn is formed and promotes generating oxygen-containing substances on SnO 2. •The spillover effect of Pd enhances the formation of O ads on Pd/SnO 2 /C. •In-situ ATR-IR confirms that less CO ads (i.e., CO M , CO B) are adsorbed on Pd/SnO 2 /C. •The introduction of SnO 2 kinetically accelerates the mass transfer of formic acid. [ABSTRACT FROM AUTHOR]

Recently, Pt-based catalysts on mixed carbon supporters have been introduced for enhancement of the formic acid oxidation (FAO) reaction. Herein, carbon black (CB) and carbon nanotubes (CNT) were combined as a hybrid CB-CNT carbon support. The Brunauer–Emmett–Teller (BET) surface area of CB-CNT support presented the increased pore size and volume, providing high surface areas for electroactive species diffusion. By cyclic voltammetry (CV), the noble metals (M) including platinum (Pt), palladium (Pd), gold (Au), and ruthenium (Ru) were utilized for catalytic electrodepositing on the CB-CNT support to obtain the catalysts. The M/CB-CNT and PtM/CB-CNT catalysts prepared under the controlled condition were characterized and compared their activities and stabilities. Among the prepared catalysts, the small particle sizes of PtM/CB-CNT, which occurred with high Pt(111) intensities from face-centered cubic (fcc) structure, were confirmed by X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). Also, the X-ray photoelectron spectroscopy (XPS) indicated the highest peak ratio of metallic Pt from PtPd/CB-CNT that was related to its high catalytic active surfaces. In the monometallic systems, the Pt/CB-CNT and Pd/C-CNT catalysts actively promote the oxidation of formic acid molecules by their unique pathways. Among the prepared catalysts in both mono- and bimetallic systems, PtPd/CB-CNT showed the highest current intensity of 11.48 mA cm−2 at a potential of 0.70 V in FAO reaction for formic acid oxidation. Although Pt/CB-CNT provided the lowest potential at maximum current intensity (ECO = 0.51 V), PtPd/CB-CNT astonishingly presented the highest active surface area (ECSACO = 0.57 cm2) for CO oxidation. The PtPd/CB-CNT catalyst showed the co-existence between Pt and Pd nanoparticles, and the hybrid structure of CB-CNT provided the improved electrochemical results towards FAO reaction. [ABSTRACT FROM AUTHOR]

The development of an efficient catalyst for formic acid electrocatalytic oxidation reaction (FAEOR) is of great significance to accelerate the commercial application of direct formic acid fuel cells (DFAFC). Herein, palladium phosphide (PdxPy) porous nanotubes (PNTs) with different phosphide content (i.e., Pd3P and Pd5P2) are prepared by combining the self‐template reduction method of dimethylglyoxime‐Pd(II) complex nanorods and succedent phosphating treatment. During the reduction process, the self‐removal of the template and the continual inside–outside Ostwald ripening phenomenon are responsible for the generation of the one‐dimensional hollow and porous architecture. On the basis of the unique synthetic procedure and structural advantages, Pd3P PNTs with optimized phosphide content show outstanding electroactivity and stability for FAEOR. Importantly, the strong electronic effect between Pd and P promotes the direct pathway of FAEOR and inhibits the occurrence of the formic acid decomposition reaction, which effectively enhances the FAEOR electroactivity of Pd3P PNTs. In view of the facial synthesis, excellent electroactivity, high stability, and unordinary selectivity, Pd3P PNTs have the potential to be an efficient anode electrocatalyst for DFAFC. [ABSTRACT FROM AUTHOR]

The synthesis of Pd nanocrystals of controlled size and morphology has drawn enormous interest due to their catalytic activity. We report a new and efficient strategy for the one-step synthesis of monodispersed Pd nanocubes with ethylenediamine tetramethylene phosphonate (EDTMP) as a complex-forming and capping agent. The morphology, structure, and growth mechanism of the Pd nanocubes were fully characterized via selected area electron diffraction (SAED), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). It was found that the morphology of the Pd nanocrystals in the proposed EDTMP-PdCl system could be changed from octahedrons to nanocubes simply by adjusting the amount of iodide used during synthesis. After UV/ozone and electrochemical cleaning, the as-prepared Pd nanocubes demonstrated excellent electrocatalytic activity and stability during formic acid oxidation, owing to their abundant {100} facets and small particle size. [ABSTRACT FROM AUTHOR]

The carbon supporting materials play a crucial role for improving the utilization and electrocatalytic activity of noble metal nanocrystals. In this work, the high-quality carbon nanobowls (CNBs) with high surface area are synthesized successfully by a simple sol–gel synthetic method. Then, the as-prepared CNBs are used as advanced supporting material to anchor Pd nanocrystals by a facile homogeneous precipitation–reduction method. The as-prepared CNBs supported Pd nanocrystals (Pd/CNBs) nanohybrids are examined thoroughly by various physical characterizations. Physical measurements display that the CNBs facilitate the dispersion and anchorage of Pd nanocrystals due to their high surface area and abundant O-containing surface groups. Cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry measurements reveal that the Pd/CNBs nanohybrids have higher electrocatalytic activity and durability for the formic acid electro oxidation than Vulcan XC-72 carbon supported Pd nanocrystals (Pd/C-72) nanohybrids and commercial Pd/C electrocatalyst. [ABSTRACT FROM AUTHOR]

Nanostructured palladium (Pd) supported on carbon (Vulcan XC-72) substrate, prepared via carbonyl chemical route, showed Pd-mass depending morphology, reflected on the surface electrochemistry via cyclic, CO-stripping voltammograms, and performance in direct formic acid and direct methanol micro laminar flow fuel cell arrangement. Comparison was done with commercial Pd/C (30 wt.%, ETEK) catalyst. The formic acid oxidation reaction (FAOR) studied in different acid media (0.1 M HClO 4 , 0.5 M H 2 SO 4 and 0.5 M H 3 PO 4 ), indicated an enhanced FAOR activity on nanowire-like as compared to nanoparticles and nanorods as well as the commercial one in each electrolyte. Besides, the nanowire-like Pd/C catalyst also favored methanol (MOR) in 0.1 M KOH. These facts confirm favorable morphological effect of nanowires for organic fuel oxidation in both acid and alkaline media. [ABSTRACT FROM AUTHOR]

Trioctylphosphine is firstly introduced in the CO-assisted solvothermal method to synthesize uniform Pd nanotetrahedrons, which are surface-doped with Pt atoms for highly efficient electrocatalytic oxygen reduction and formic acid oxidation. [Display omitted] • TOP is firstly introduced in the CO-assisted Pd shape-controlled synthetic method. • Small-sized, uniform, and highly selective Pd NTs are obtained via this method. • Pd NTs are surface-doped with Pt atoms by the modified Pt2+ galvanic replacement. • Pd/SDPt NTs exhibit highly efficient ORR and FAOR electrocatalytic performance. • The structure-function relations are studied both experimentally and theoretically. Increasing the accessible active sites and especially improving the intrinsic activity are two major effective strategies for enhancing the electrocatalytic activity of nanomaterials. Accordingly, through the trioctylphosphine (TOP)-based CO-assisted solvothermal method and the small-amount Pt2+ galvanic replacement, highly uniform Pd nanotetrahedrons (NTs) with Pt-doped surfaces are synthesized and supported onto carbon black. Comprehensive experimental and theoretical analyses reveal that, owing to the Pt surface-doped (SD) nanostructure, the conformal formation of surface Pt {111} facets, as well as the strain and electronic effects induced by the Pd–Pt alloy structure, Pd/SDPt NTs/C exhibits much better electrocatalytic performance than Pd NTs/C, commercial Pd/C, and Pt/C toward both oxygen reduction and formic acid oxidation reactions, showing greatly improved metal utilization and area/mass-specific activity. This study develops a high-performance bifunctional electrocatalyst, and firstly introduces TOP as the easy-removable surface-energy adjuster for the Pd shape-controlled synthesis, which may be further expanded to other metals and shapes. [ABSTRACT FROM AUTHOR]

Abstract: The oleylamine (OAm)-functionalized Pd nanoparticles (Pd–OAm) have been conveniently synthesized through direct thermal decomposition method of low cost palladium acetate. The morphology, crystalline structure and composition of the Pd–OAm are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Fourier transform infrared (FT-IR) spectroscopy, XPS and zeta potential analysis confirm the successful immobilization of OAm molecules on the Pd nanoparticles surface. The Pd–OAm displays an enhanced electrocatalytic activity and formic acid-tolerant ability for the oxygen reduction reaction (ORR), suggesting a potential application in cathodic catalyst for direct formic acid fuel cells. [Copyright &y& Elsevier]