《Small》: Locally Topological Disorder of Ag Sites in Medium-Entropy Alloys for Methanol Electrocatalytic Oxidation

Qing Hu,⁺ Peipei Li,⁺ Mengqian Li,⁺ Jiacong Wu, Wenya Fan, Haochen Zhang, Xingchen Jiao, and Qingxia Chen*

Pd-based nanostructures are emerging as novel catalysts for alkaline direct methanol fuel cells (ADMFCs), but enhancing their activity and stability for electrocatalytic methanol oxidation reaction (MOR) remains a significant challenge. Herein, the medium-entropy principle is employed to modify the structure of Pd-based catalysts. An electrospinning method combined with subsequent thermal treatment is proposed to synthesize PtPdCuAg medium-entropy alloy (MEA) nanoparticles dispersed on carbon nanofibers (CNFs) (PtPdCuAg MEAs/CNFs). During the in situ electrochemical activation process, Ag migrates to the surface of PtPdCuAg MEAs, forming an Ag-rich outer layer. The incorporation of various elements to create the medium-entropy structure lowers the d-band center of the catalyst. Moreover, the Ag skin facilitates the formation of oxygen-containing intermediates, which can further oxidize toxic intermediates, thereby refreshing the catalyst surface. Additionally, the 1D CNF substrates effectively prevent the aggregation and sintering of MEA catalysts. Consequently, PtPdCuAg MEAs/CNFs demonstrate an enhanced MOR activity of 1598.5 mA mg−1 under alkaline conditions, which is 2.5 and 3.1 times higher than that of PtPdCu MEAs/CNFs and commercial Pd/C catalysts, respectively. This work not only provides a facile route to fabricate Pd-based MEAs but also highlights the critical role of Ag in MOR, greatly advancing the application of ADMFCs.

Figure 1. Schematic illustration of MOR performance enhancement induced by the locally topological disorder of Ag sites and synergistic effect between various elements in PtPdCuAg MEAs/CNFs.