Facile synthesis of PdSn alloy octopods through the Stranski–Krastanov growth mechanism as electrocatalysts towards the ethanol oxidation reaction

Abstract

Pd-based nano-catalysts are critical to the commercialization of direct ethanol fuel cells (DFECs), however, the synthesis of Pd-based binary alloy nanocrystals with well-defined branches is still a great challenge. Here...

Interfacial Engineering of Porous Pd/M (M = Au, Cu, Mn) Sponge-like Nanocrystals with a Clean Surface for Enhanced Alkaline Electrochemical Oxidation of Ethanol

“…All electrocatalysts reveal the main voltammogram characteristics of Pd in alkaline electrolyte, with a sharp reduction peak of PdM–O reduction between 0.06 and −0.70 V during the cathodic sweep (Figure a). The reduction peak of PdM–O in the PdM catalysts and Pd shifted significantly to lower potentials relative to the commercial Pd/C catalyst, which implies the easy formation of oxygenated species on PdM and Pd that are highly important for accelerating EOR kinetics. − ,,− The electrochemical CO stripping was measured on PdCu, AuPd, and PdMn nanocrystals and Pd/C, which reveals the CO oxidation at potential range (−0.35 to 0.20 V), but with a higher CO-poisoning tolerance activity on PdCu (Figure S5). The PdCu shows a more negative onset potential ( E Onset ) of −0.36 V compared to AuPd (−0.17 V), PdMn (−0.20 V), and Pd/C (−0.26 V), indicating facile CO oxidation of PdCu among others that is attributable to the steadiness of the Pd with increased active sites by the Cu integration (Figure S5).…”

“…The PdM nanocrystals show less anodic onset potentials (i.e., PdCu (−0.68 V), AuPd (−0.62 V), and PdMn (−0.64 V) than that of Pd (−0.58 V) and commercial Pd/C catalysts (−0.44 V), which imply quick EOR kinetics at lower energies, resulting from the modulated electronic state of Pd by M elements, shown by the linear sweep voltammogram (LSV) curves (Figure c). Moreover, the electronic interaction between the two metals facilitates the generation of adsorbed − OH species, due to the higher oxophilicity of M than Pd resulting in fast EOR kinetics on the PdM. − ,,− …”

“…For instance, the EOR mass activity of PdAg anchored on a multiwalled carbon nanotube (Pd 3.5 Ag/MWCNT) (3.72 A/mg Pd ) was 7.54 times higher than a commercial Pd/C catalyst (0.49 A/mg Pd ), due to the alloying effect and high dispersion of Pd 3.5 Ag, besides its improved electronic interaction with MWCNT . The EOR mass activity of Pd 72 Sn 28 octopods (2.70 A/mg Pd ) was 2.1 times greater than that of commercial Pd/C, owing to the octopod morphology and the decreased d-band center of the {100} surface of the Pd 72 Sn 28 , which weakened the adsorption of the acetate-evolution intermediate (*CH 3 CO) as confirmed by the density functional theory (DFT) simulation . Fe, Cu, Co, and Mn are well-known for their abundance on the earth surface, low cost, safety, incredible ability to activate a C–C bond, and ease of alloying with Pd to counterbalance high EOR activity and CO poisoning resistance.…”

“…34 The EOR mass activity of Pd 72 Sn 28 octopods (2.70 A/mg Pd ) was 2.1 times greater than that of commercial Pd/C, owing to the octopod morphology and the decreased d-band center of the {100} surface of the Pd 72 Sn 28 , which weakened the adsorption of the acetate-evolution intermediate (*CH 3 CO) as confirmed by the density functional theory (DFT) simulation. 35 Fe, Cu, Co, and Mn are well-known for their abundance on the earth surface, low cost, safety, incredible ability to activate a C−C bond, and ease of alloying with Pd to counterbalance high EOR activity and CO poisoning resistance. For instance, Pd− Cu/C had enhanced EOR activity by 1.5 times compared to that of Pd/C, owing to the bifunctional effect and interaction with C-support.…”

“…The current approaches for the formation of Pd-based alloys, like hydrothermal treatment, seed-mediated growth, and galvanic replacement, comprise multiple reaction steps, heating, and the use of organic solvents or surfactants. − ,,− These methods not only allow metal segregation instead of their mixing at the atomic level, but also form alloy structures with a capped surface by the surfactants, which devalue their catalytic activity, besides phase engineering of the nanocatalysts. − Also, it is still ambiguous whether the synergetic effect or strain effect in a Pd-based alloy is preferred for the EOR electrocatalysis.…”