Theoretical study of the oxidation of formic acid on a PtPd(111) surface

By performing density functional theory calculations, the adsorption configurations of formic acid and possible reaction pathway for HCOOH oxidation on PtPd(111) surface are located. Results show that CO2 is preferentially formed as the main product of the catalytic oxidation of formic acid. The formation of CO on the pure Pd surface could not possibly occur during formic acid decomposition on the PtPd(111) surface owing to the high reaction barrier. Therefore, no poisoning of catalyst would occur on the PtPd(111) surface. Our results indicate that the significantly increased catalytic activity of bimetallic PtPd catalyst towards HCOOH oxidation should be attributed to the reduction in poisoning by CO.

Electrochemically induced surface metal migration in well-defined core-shell nanoparticles and its general influence on electrocatalytic reactions

Bimetallic nanoparticle catalysts provide enhanced activity, as combining metals allows tuning of electronic and geometric structure, but the enhancement may vary during the reaction because the nanoparticles can undergo metal migration under catalytic reaction conditions. Using cyclic voltammetry to track the surface composition over time, we carried out a detailed study of metal migration in a well-defined model Au-Pd core-shell nanocatalyst. When subjected to electrochemical conditions, Au migration from the core to the shell was observed. The effect of Pd shell thickness and electrolyte identity on the extent of migration was studied. Migration of metals during catalytic ethanol oxidation was found to alter the particle's surface composition and electronic structure, enhancing the core-shell particles' activity. We show that metal migration in core-shell nanoparticles is a phenomenon common to numerous electrochemical systems and must be considered when studying electrochemical catalysis.

A novel approach for the in situ synthesis of Pt-Pd nanoalloys supported on Fe3O4@C core-shell nanoparticles with enhanced catalytic activity for reduction reactions

A facile two-step synthesis method has been developed for the synthesis of highly active and well-defined Pt-Pd nanoalloys supported on the surface of Fe3O4@C colloidal nanoparticles. The nanoalloys were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) with line scanning of energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy. The nanoalloys exhibit remarkable catalytic activity toward reduction of 4-nitrophenol to 4-aminophenol by NaBH4. Furthermore, the catalytic activity of the supported nanoalloys could be further optimized by tuning the composition of the supported nanoalloys, and the optimized catalytic activity is obtained with a normalized rate constant of about 12.03 nmol(-1) s(-1) when the atomic ratio of Pd to Pt is tuned to 2.07:1, which is advancing among the Pd-based nanocatalysts reported in the recent years.

Electrocatalysis of formic acid on palladium and platinum surfaces: from fundamental mechanisms to fuel cell applications

A brief overview is presented on recent progress in mechanistic studies of formic acid oxidation, synthesis of novel Pd- and Pt-based nanocatalysts and their practical applications in direct formic acid fuel cells.

Enhancing the catalytic and electrocatalytic properties of Pt-based catalysts by forming bimetallic nanocrystals with Pd

Bimetallic nanocrystals consisting of two distinct metals such as Pd and Pt are attractive for a wide variety of catalytic and electrocatalytic applications as they can exhibit not only a combination of the properties associated with both metals but also enhancement or synergy due to a strong coupling between the two metals. With Pd as the base metal, many methods have recently been demonstrated for the synthesis of Pd-Pt bimetallic nanocrystals having a wide variety of different structures in the form of alloys, dendrites, core-shells, multi-shells, and monolayers. In this tutorial review, we begin with a brief discussion on the possible structures of Pd-Pt bimetallic nanocrystals, followed by an account of recent progress on synthetic approaches to such nanocrystals with controlled structures, shapes and sizes. In addition to the experimental procedures and mechanistic studies, a number of examples are presented to highlight the use of such bimetallic nanocrystals as catalysts or electrocatalysts for various applications with enhanced performance relative to their monometallic counterparts.