Pd‐Enriched‐Core/Pt‐Enriched‐Shell High‐Entropy Alloy with Face‐Centred Cubic Structure for C₁ and C₂ Alcohol Oxidation

Abstract

High-entropy alloy nanoparticles (HEA NPs) have aroused great interest globally with their unique electrochemical, catalytic, and mechanical properties, as well as diverse activity and multielement tunability for multi-step reactions. Herein, a facile low-temperature synthesis method at atmospheric pressure is employed to synthesize Pd-enriched-HEA-core and Pt-enriched-HEA-shell NPs with a single phase of face-centred cubic structure. Interestingly, the lattice of both Pd-enriched-HEA-core and Pt-enriched-HEA-shell enlarge during the formation process of HEA, with tensile strains included in the core and shell of HEA. The as-obtained PdAgSn/PtBi HEA NPs show excellent electrocatalytic activity and durability for methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). The specific (mass) activity of PdAgSn/PtBi HEA NPs for MOR is 4.7 mA cm À 2 (2874 mA mg (Pd + Pt)À 1 ), about 1.7 (5.9) and 1.5 (4.8) times higher than that of commercial Pd/C and Pt/C catalysts, respectively. Additional to high-entropy effect, Pt sites and Pd sites on the interface of the HEA act synergistically to facilitate the multi-step process towards EOR. This study offers a promising way to find a feasible route for scalable HEA manufacturing with promising applications.

Assembly of Alloyed PdM (Ag, Cu, and Sn) Nanosheets and Their Electrocatalytic Oxidation of Ethanol and Methanol

“…The catalytic mechanism of Pd-based catalysts for EOR includes two pathways for the reaction, namely, the C1 process and the C2 process. 46 The C1 process is the process by which ethanol can be completely converted to carbon dioxide by the transfer of 12 electrons, and this process requires a great amount of energy, as shown in Scheme 2. The end products of Pd-based catalysts for methanol are water and carbon dioxide.…”

“…Generally, the potential barrier for electron transfer decreases accordingly with increasing temperature, thus accelerating all electrocatalytic reaction steps of EOR, especially in the decisive reaction rate. The Arrhenius plots are represented in Figure S10a where the relationship between ln [Current density mA mg Pd –1 ] and 1/ T is plotted according to the Arrhenius formula as follows: i = A e − E normala / R T where i represents the current density, R is the universal gas constant, T is the reaction temperature in Kelvins, and E a is the activation energy of the particular reaction. The concentration of KOH and CH 3 CH 2 OH plays a significant role in the EOR, and the corresponding current density will also increase significantly with the increase of the KOH and ethanol concentration.…”

“…45 Due to the different atomic radii of the second metal, when introduced into the fcc crystal of Pd, different lattice changes are induced. 46,53 As depicted in Figure 2b, the enlarged XRD patterns show the shift of the characteristic diffraction peaks occurring near the (111) crystal plane for the bimetallic alloy. When silver atoms are introduced into the lattice, a slight lattice expansion is induced in the crystal due to the silver atom radius being slightly larger than the radius of the Pd atom, which mainly shows tensile strain.…”

“…Numerous products can be generated, such as incompletely oxidized acetaldehyde with acetic acid. Under alkaline conditions, the electro-oxidation reactions of ethanol may include: ,, CH 3 CH 2 OH + 2OH − → CH 3 CHO + 2H 2 normalO + 2e − CH 3 CH 2 OH + 5OH − → CH 3 COO − + 4H 2 normalO + 4e − CH 3 CH 2 OH + 16 OH − → 2CO 3 2 − + 11 normalH 2 normalO + 12 normale − …”

“…Numerous products can be generated, such as incompletely oxidized acetaldehyde with acetic acid. Under alkaline conditions, the electro-oxidation reactions of ethanol may include: ,, …”