Mesoporous High-Entropy\nAlloy Films

High-entropy alloys (HEAs) are promising materials for\nelectrochemical\nenergy applications due to their excellent catalytic performance and\ndurability. However, the controlled synthesis of HEAs with a well-defined\nstructure and a uniform composition distribution remains a challenge.\nHerein, a soft template-assisted electrodeposition technique is used\nto fabricate a mesoporous HEA (m-HEA) film with a uniform composition\ndistribution of Pt, Pd, Rh, Ru, and Cu, providing a suitable platform\nfor investigating structure–performance relationships. Electrochemical\ndeposition enables the uniform nucleation and grain growth of m-HEA,\nwhich can be deposited onto many conductive substrates. The m-HEA\nfilm exhibits an enhanced mass activity of 4.2 A mg<sub>Pt</sub><sup>–1</sup> toward methanol oxidation reaction (MOR), which is\n7.2-fold and 35-fold higher than a mesoporous Pt film and commercial\nPt black, respectively. Experimental characterization indicates that\nstructural defects and a low work function of the m-HEA film offer\nsufficient active sites and fast electron-transfer kinetics. Furthermore,\ntheoretical calculations demonstrate that the variety of favorable\nadsorption sites on multimetallic elements of HEA reduces the barriers\nfor dehydration pathways and *CO species removal, ensuring optimal\nperformance for complex MOR reactions. This work provides an effective\napproach to designing a variety of HEA catalysts with well-controlled\nporous structures for targeted electrocatalytic applications.