Cascaded p-d Orbital Hybridization Interaction in Ultrathin High-Entropy Alloy Nanowires Boosts Complete Non-CO Pathway of Methanol Oxidation Reaction

Abstract

Designing high efficiency platinum (Pt)-based catalysts for methanol oxidation reaction (MOR) with high "non-CO" pathway selectivity is strongly desired and remains a grand challenge. Herein, PtRuNiCoFeGaPbW HEA ultrathin nanowires (HEA-8 UNWs) are synthesized, featuring unique cascaded p-d orbital hybridization interaction by inducing dual p-block metals (Ga and Pb). In comparison with Pt/C, HEA-8 UNWs exhibit 15.0- and 4.2-times promotion of specific and mass activity for MOR. More importantly, electrochemical in situ FITR spectroscopy reveals that the production/adsorption of CO (CO^*) intermediate is effectively avoided on HEA-8 UNWs, leading to the complete "non-CO" pathway for MOR. Theoretical calculations demonstrate the optimized electronic structure of HEA-8 UNWs can facilitates a lower energy barrier for the "non-CO" pathway in the MOR.

Keywords: cascaded p–d orbital hybridization; high‐entropy alloy; methanol oxidation reaction; non‐CO pathway; ultrafine nanowires.

Figure 1

a) TEM and b) HAADF–STEM images of HEA‐8 UNWs. c) Aberration‐corrected STEM image of HEA‐8 UNWs. d) TEM and e) HAADF–STEM images of HEA‐6 UNWs. f) Aberration‐corrected STEM image of HEA‐6 UNWs. HAADF–STEM and EDS mapping images of g) HEA‐8 UNWs and h) HEA‐6 UNWs. i) The components of HEA‐8 UNWs and HEA‐6 UNWs. The Pt 4f XPS spectra of j) HEA‐8 UNWs and k) HEA‐6 UNWs.

Figure 2

a) Cyclic voltammogram curves of HEA‐8 UNWs, HEA‐6 UNWs, and Pt/C in 0.5 m H₂SO₄ + 2 m CH₃OH. b) The comparison of catalytic performances. c) The plots of forward peak current J (mA µg_Pt ⁻¹) versus the square root of the scan rate (v ^1/2) for MOR. d) The comparison of the slope of (c). e) i–t curves (at 0.6 V vs RHE) and f) the normalized current after various CV cycles for HEA‐8 UNWs, HEA‐6 UNWs, and Pt/C.

Figure 3

CO–DRIFTS spectra of a) HEA‐8 UNWs, b) HEA‐6 UNWs and c) Pt/C. N₂‐purging CO–DRIFTS spectra of d) HEA‐8 UNWs, e) HEA‐6 UNWs and f) Pt/C. Electrochemical in situ FTIR spectra of g) HEA‐8 UNWs, h) HEA‐6 UNWs, and i) Pt/C. Potential dependent j) amount of HCOOH and k) Faraday efficiency (FE) on HEA‐8 UNWs and HEA‐6 UNWs.

Figure 4

The PDOSs of a) HEA‐8 UNWs. b) The site‐dependent PDOSs of Pt Co and Fe. c) The DOS of Pt, PtGa, PtPb, and PtGaPb in HEA‐8 UNWs. The PDOS of d) CH₃OH adsorption and e) H₂O adsorption. f) The charge density difference of CO adsorption and OH adsorption. g) The adsorption energy of ^*OH and ^*CO on three different catalysts. h) The variation of Gibbs free energy of the MOR.