Interfacial electronic and strain modulation in core-shell CuNi2Sn@PtFeSn heterojunctions with exposed PtFeSn(102) facets for highly efficient ethanol oxidation.

The ethanol oxidation reaction (EOR) at the anode of direct ethanol fuel cells (DEFCs) remains challenging due to the difficulty of achieving complete oxidation to CO2. Herein, we report a core-shell CuNi2Sn@PtFeSn/C heterojunction high-entropy alloy (HEA, CuNi2Sn core, PtFeSn shell) with exposed PtFeSn(102) facets for EOR. The engineered heterointerface simultaneously modulates the Pt electronic structure, induces favorable lattice strain, and promotes synergistic interactions among Pt, Fe, Sn, Cu, and Ni. CuNi2 Sn@PtFeSn/C exhibits a high mass activity of 8.54 A mgPt-1 for the ethanol oxidation reaction, which is 9.93 times higher than that of 20 wt% Pt/C, while retaining excellent activity after 43,200 s of continuous operation. Characterizations reveal that the moderate interfacial electron redistribution and lattice strain weaken CO adsorption, facilitate ethanol dehydrogenation, and promote CO2 formation through the C1 pathway. Density functional theory (DFT) calculations further demonstrate that the core-shell heterointerface optimizes deprotonation kinetics, reduces the CO adsorption strength, and lowers the energetic barrier for complete ethanol oxidation. This work highlights heterointerface and strain engineering in Pt-based high-entropy alloys as an effective strategy for designing efficient and durable electrocatalysts for complete ethanol oxidation.