Length-tunable Pd2Sn@Pt core-shell nanorods for enhanced ethanol electrooxidation with concurrent hydrogen production

Abstract

The electrooxidation of ethanol as an alternative to the oxygen evolution reaction presents a promising approach for low-cost hydrogen production. However, the design and synthesis of efficient ethanol oxidation electrocatalysts remain key challenges. Here, a colloidal procedure is developed to prepare Pd₂Sn@Pt core-shell nanorods with an expanded Pt lattice and tunable length. The obtained Pd₂Sn@Pt catalysts exhibit superior activity and stability for ethanol electrooxidation compared to Pd₂Sn and commercial Pt/C catalysts. By tuning the length of the Pd₂Sn@Pt nanorods, remarkable mass activity of up to 4.75 A mg_Pd+Pt^-1 and specific activity of 20.14 mA cm^-2 are achieved for the short nanorods owing to their large specific surface area. A hybrid electrolysis system for ethanol oxidation and hydrogen evolution is constructed using Pd₂Sn@Pt as the anodic catalyst and Pt mesh as the cathode. The system requires a low cell voltage of 0.59 V for the simultaneous production of acetic acid and hydrogen at a current density of 10 mA cm^-2. Density functional theory calculations further reveal that the strained Pt shell reduces energy barriers in the ethanol electrooxidation pathway, facilitating the conversion of ethanol to acetic acid. This work provides valuable guidance for developing highly efficient ethanol electrooxidation catalysts for integrated hydrogen production systems.

Fig. 1. (a–c) TEM micrographs of (a) Pd₂Sn-s@Pt, (b) Pd₂Sn-m@Pt, (c) Pd₂Sn-l@Pt and (d) their XRD patterns. (e) HRTEM image of Pd₂Sn-s@Pt and (f) integrated pixel intensity of the crystal phase taken from the dotted rectangle in (e) panel. (g) STEM image and corresponding EDS elemental mappings of Pd₂Sn-s@Pt. (h) HRTEM image of Pd₂Sn-l@Pt and (i) integrated pixel intensity of the crystal phase taken from the dotted rectangle in (h) panel. (j) STEM image and corresponding EDS elemental mappings of Pd₂Sn-l@Pt. (k and l) EDS line scan across the Pd₂Sn-s@Pt (l) as indicated by the dashed line in STEM image shown in (k). (m and n) EDS line scan across the Pd₂Sn-l@Pt (n) as indicated by the dashed line in STEM image shown in (m).

Fig. 2. XPS spectrum of Pd₂Sn-s@Pt and Pd₂Sn-s in the (a) Pd 3d, (b) Sn 3d and (c) Pt 4f regions.

Fig. 3. (a and b) CV curves of catalysts in a 1 M KOH solution (a) and in a 1 M KOH + 1 M ethanol solution (b). (c) Comparison of specific and mass activities of the catalysts. (d) CA profile of catalysts in a 1 M KOH + 1 M ethanol solution. (e) CA curves of catalysts with CV reactivation every 1000 s. (f) ¹H NMR analysis of the electrolytes before and after CA measurements for Pd₂Sn-s@Pt catalyst.

Fig. 4. (a and b) Schematic illustration for the ethanol oxidation pathway on (a) Pt (111) and (b) strained Pt (111) surfaces. (c and d) Free energy diagrams for electrochemical EOR on the (c) Pt (111) and (d) strained Pt (111) surfaces.

Fig. 5. (a) Schematic diagram of the two-electrode electrolyzer. (b) LSV curves and (c) CA curves of the cell in 1 M KOH containing 1 M ethanol electrolyte. (d) LSV curves of Pd₂Sn-s@Pt before and after 12 h CA measurement with reactivation.