H₂Reduction Annealing Induced Phase Transition and Improvements on Redox Durability of Pt Cluster-Decorated Cu@Pd Electrocatalysts in Oxygen Reduction Reaction

Abstract

Hierarchical structures in shell with transition metal underneath is a promising design for high-performance and low-cost heterogeneous nanocatalysts (NCs). Such a design enables the optimum extent of synergetic effects in NC surface. It facilitates intermediate reaction steps and, therefore, boosts activity of NC in oxygen reduction reaction (ORR). In this study, carbon nanotube (CNT)-supported ternary metallic NC comprising Cu cluster -in-Pd cluster nanocrystal and surface decoration of atomic Pt clusters (14 wt %) is synthesized by using the wet chemical reduction method with sequence and reaction time controls. By annealing in H 2 environment (H 2 /N 2 = 9:1, 10 sccm) at 600 K for 2 h, specific activity of Cu@Pd/Pt is substantially improved by ∼2.0-fold as compared to that of the pristine sample and commercial Pt catalysts. By cross-referencing results of electron microscopic, X-ray spectroscopic, and electrochemical analyses, we demonstrated that reduction annealing turns ternary NC into complex of Cu 3 Pt alloy and Cu x Pd 1– x alloy. Such a transition preserves Pt and Pd in metallic phases, therefore improving the activity by ∼29% and the stability of NC in an accelerated degradation test (ADT) as compared to those of pristine Cu@Pd/Pt in 36 000 cycles at 0.85 V (vs RHE). This study presents robust H 2 annealing for structure stabilization of NC and systematic characterizations for rationalization of the corresponding mechanisms. These results provide promising scenarios for facilitation of heterogeneous NC in ORR applications.

High-Performance and Stable Hydrogen Evolution Reaction Achieved by Pt Trimer Decoration on Ultralow-Metal Loading Bimetallic PtPd Nanocatalysts

“…Such a behavior could be attributed to the competition of nucleation and crystal growth of Pt and Pd atoms by their differences in the concentration and material nature. Given that Pt atoms tend to segregate to the surface during H 2 annealing, , formation of surface atomic Pt cluster decoration is expectable and is consistently revealed in XAS analysis. Because of the limited loading and homoatomic clustering, Pt atoms will tend to form nanoislands with a low stack coverage on the Pd surface.…”

Structure and Migration Mechanisms of Small Vacancy Clusters in Cu: A Combined EAM and DFT Study

“…Copper is a typical face-centered cubic (fcc) metal with a wide range of electronic [1] and electrochemical [2,3] applications due to its reliability, low resistivity, and high thermal and electrical conductivity [1,4]. It is often used at elevated temperatures or in high-stress conditions [4].…”

High Performing Chemically Ordered Pt2CoNi/Ti@C as an Efficient and Stable Cathode Catalyst for Oxygen Reduction

“…Among the various electrocatalytic systems, platinum (Pt)-based catalysts have been well established in fuel cell technology. These noble-metal nanoparticles show exceptional significance from the perceptions of both research and development of energy due to their distinctive catalytic role in reactions such as hydrogen evolution (HER) and oxygen reduction (ORR). − Contemporarily, in the search for pollution-free energy systems, polymer electrolyte membrane (PEM) fuel cells have also gained increased importance in various stationary and automotive applications. Nevertheless, their advances remain largely hindered owing to the sluggish ORR kinetics, even with the use of Pt as the catalyst.…”