Strongly Coupled Pd Nanotetrahedron/Tungsten Oxide Nanosheet Hybrids with Enhanced Catalytic Activity and Stability as Oxygen Reduction Electrocatalysts

Abstract

The design and synthesis of highly active oxygen reduction reaction (ORR) catalysts with strong durability at low cost is extremely desirable but still remains a significant challenge. Here we develop an efficient strategy that utilizes organopalladium(I) complexes containing palladium-palladium bonds as precursors for the synthesis of strongly coupled Pd tetrahedron-tungsten oxide nanosheet hybrids (Pd/W18O49) to improve the electrocatalytic activity and stability of Pd nanocrystals. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of Pd tetrahedral nanocrystals on the in situ-synthesized W18O49 nanosheets. Compared to supportless Pd nanocrystals and W18O49, their hybrids exhibited not only surprisingly high activity but also superior stability to Pt for the ORR in alkaline solutions. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrochemical analyses indicated that the enhanced electrocatalytic activity and durability are associated with the increased number and improved catalytic activity of active sites, which is induced by the strong interaction between the Pd tetrahedrons and W18O49 nanosheet supports. The present study provides a novel strategy for synthesizing hybrid catalysts with strong chemical attachment and electrical coupling between nanocatalysts and supports. The strategy is expected to open up exciting opportunities for developing a novel class of metal-support hybrid nanoelectrocatalysts with improved ORR activity and durability for both fuel cells and metal-air batteries.

Face the Edges: Catalytic Active Sites of Nanomaterials

“…When the proper metal core is selected, optimization of homogeneous catalyst relies mainly on altering the ligands around metal to tune the electronic structure to achieve suitable binding or releasing. For “metal on support” catalyst, to tune the performance requires the optimization of metals and selection of supports, while the supports are not innocent during catalytic reactions in many cases 22, 23, 24. For NPs as catalysts, the optimizations of their performances are mainly achieved by tailoring their morphologies.…”

“…The SMSI effects are detrimental in many cases,88, 89 thus researchers would like to avoid them and choose inert supports in early studies. Recently, more and more examples16, 22, 23, 90, 91 proved that the supports might promote some reactions and enhance the total catalytic activities.…”

“…The multicomponent interface may owe their origin of activities to the “coordinate unsaturated” 93. In other cases, there are many beneficial SMSI effects on metal oxides support metals,23, 111 and sometimes the enhanced performance cannot simply derive from “coordinate unsaturated”. When using reductive metal oxides as supports, the reducing nature of supports would whether donate or withdraw charges from metals near the metal/oxide interface, depending on the work functions of two materials 22.…”

Octahedral PtNi nanoparticles with controlled surface structure and composition for oxygen reduction reaction

“…Linear-sweep voltammetry (LSV) measurements were conducted under an oxygen atmosphere by sweeping the potential from 0.1 V (vs. RHE) anodically to 1.1 V at a scan rate of 20 mV s −1 and a rotation speed of 1600 rpm. The electrocatalytic activity of catalysts was compared by their mass-and area-specific activities using the mass-transport correction for thin-film RDEs [17,18]:…”

Preparation and Electrocatalytic Characteristics of PdW/C Catalyst for Ethanol Oxidation

“…It has been claimed that tungsten (W) oxide was a suitable promoter for noble metal catalyst, leading to a significant decrease in poisoning species (CO) [23,24]. The presence of W species is expected to assist in the electro-oxidation of poisonous reaction intermediates adsorbed on the active Pd sites [25,26].…”