Heterogeneous doping is one effective strategy for synthesizing metal alloy nanowires. Herein, the heterogeneous doping processes of Pd on the ultrathin Au nanowires were systematically modulated and investigated. Au-Pd alloy nanowires with various morphologies and lattice structures can be obtained by adjusting the morphology of the precursor Au nanowires and the kinetics of the heterogeneous doping processes. The effects of the rate of Pd reduction and the concentration of the ligand oleylamine (OAm) on the Pd deposition and alloying mode were articulated. Generally, as the Pd deposition rate decreases, the Pd deposition and alloying mode switches from the island-forming Stransky–Krastanov (SK) mode to the epitaxial Frank-van der Merwe (FM) mode, and eventually to an unconventional twisting alloying mode, where the interdiffusion of Pd and Au causes drastic rearrangement of the lattice structure and formation of helical structures. The kinetics-related variation of alloying mode could also be observed in the Au-Ag nanowires, demonstrating a general design principle for the synthesis of alloy nanostructures. In addition, the electrocatalytic performance of various Au-Pd nanowires was evaluated, and the alloy nanowire formed via the SK mode was found to be an excellent electrocatalyst for oxygen reduction and ethanol oxidation.

Hollow nanostructures with structural advantages have been widely exploited as catalysts in electrochemical reactions. However, there are only limited strategies for constructing hollow Pd-based nanostructures. In this work, Pd₄S hollow nanospheres (Pd₄S HNSs) are synthesized with a facile wet-chemical method via a self-templating process. Intermediate Pd-L-cysteine solid nanospheres (SNSs) were firstly obtained by the coordination of L-cysteine with Pd²⁺, and then in situ converted to hollow nanospheres in the following reduction process. The formation mechanism of the Pd₄S HNSs was studied, and the size of the Pd₄S HNSs can be readily adjusted by tuning the size of the SNSs. The hollow morphology would help the exposure of active sites and the prevention of aggregation during the catalytic reactions. As a result, the Pd₄S HNSs exhibit improved catalytic performances in the oxygen reduction reactions, with a half-wave potential of 0.913 V vs. reversible hydrogen electrode (RHE) and impressive stability in the accelerated durability test.