S-doped defective Pd{111} facets endow Au@AuPd nanowire networks with superior electrocatalytic performance for alkaline ORR

Abstract

In this work, we report the synthesis of S_4.9-doped Au_89.3@Au_1.3Pd_5.8/S^B3.8A1.1 NWNs, which are composed of Au cores and ultrathin alloyed Au–Pd shells rich in defective S-doped Pd{111}. It is found that Pd atoms in the defective Pd{111} facets are doped with an optimal ratio of S²⁻ and S₂²⁻ to form PdS₂ and Pd_2.8S compounds. Thanks to their unique structure and surface composition, the as-prepared S_4.9-doped Au_89.3@Au_1.3Pd_5.8/S^B3.8A1.1 NWNs possess abundant lattice defects, a larger ECSA, and an optimal Pd-band center, which enable them to exhibit superior ORR performance under alkaline conditions. For instance, they exhibit an impressive half-wave potential (E_1/2) of 0.949 V, which is 94 mV higher than that (0.855 V) of commercial Pt/C catalysts. Moreover, their kinetic current density (47.12 mA cm⁻²), mass activity (2.50 A mg_Pd⁻¹) and specific activity (2.41 mA cm⁻²) at 0.9 V are 15.4, 21 and 13 times higher than those (3.06 mA cm⁻², 0.12 mg_Pt⁻¹ and 0.19 mA cm⁻²) of commercial Pt/C catalysts, respectively. Furthermore, they also exhibit significantly better long-term durability than commercial Pt/C catalysts due to the enhanced oxidation resistance induced by the presence of alloyed AuPd shells doped with PdS₂ and Pd_2.8S compounds.