Epitaxial Growth of Unconventional 4H-Pd Based Alloy Nanostructures on 4H-Au Nanoribbons towards Highly Efficient Electrocatalytic Methanol Oxidation

Direct methanol fuel cells (DMFCs) hold great promise as clean energy conversion devices in the future. Noble metal nanocatalysts, renowned for their exceptional catalytic activity and stability, play a crucial role in DMFCs. Among these catalysts, Pt- and Pd-based nanocatalysts are widely recognized as the most effective catalysts for the electrochemical methanol oxidation reaction (MOR), which is the key half-cell reaction in DMFCs. However, due to the high cost of Pt- and Pd-based materials, there is a strong desire to further enhance their catalytic performance. One of the most promising approaches for it is to develop noble metal-based alloy nanocatalysts, which have shown great potential in improving electrocatalytic activity. Notably, advancements in phase engineering of nanomaterials (PEN) have revealed that noble metal-based nanomaterials with unconventional phases exhibit superior catalytic properties in various catalytic reactions compared to their counterparts with conventional phases. To obtain noble metal-based nanocatalysts with unconventional crystal phases, wet-chemical epitaxial growth has been employed as a facile and effective method, utilizing unconventional-phase noble metal nanocrystals as templates. Nevertheless, epitaxially growing bimetallic alloy nanostructures with unconventional crystal phases remains a challenge, impeding further exploration of their catalytic performance in electrochemical reactions such as MOR. In this study, we utilize 4H hexagonal phase Au (4H-Au) nanoribbons as templates for the epitaxial growth of unconventional 4H hexagonal PdFe, PdIr, and PdRu, resulting in the formation of 4H-Au@PdM (M = Fe, Ir, and Ru) core-shell nanoribbons. As a proof-of-concept application, we investigate the electrocatalytic activity of the synthesized 4H-Au@PdFe nanoribbons towards MOR, which exhibit a mass activity of 3.69 A·mg_Pd⁻¹, i.e., 10.5 and 2.4 times that of Pd black and Pt/C, respectively, placing it among the best Pd- and Pt-based MOR electrocatalysts. Our strategy opens up an avenue for the rational construction of unconventional-phase multimetallic nanostructures to explore their phase-dependent properties in various applications. © Editorial office of Acta Physico-Chimica Sinica.