A Universal Synthesis of PtPd‐Based High‐Entropy Sub‐Nanoribbons for Oxygen Reduction Electrocatalysis

ABSTRACT PtPd‐based high‐entropy alloys (HEAs) with sub‐nano‐thick ribbon morphology are a class of promising catalysts for electrochemical reactions; however, a lack of a general synthetic method that allows extensive compositional modulation for probing untold catalytic powers. Herein, we report a universal strategy for constructing PtPd‐based sub‐nanoribbons (SNRs) with tunable alloy elements for boosting oxygen reduction reaction (ORR). In this synthetic method, a ligand collection is organized to balance the large differences in redox potentials of multiple metal precursors and enforce ribbon‐like anisotropic growth. By diversifying composition, SNRs can be tuned from low‐entropy alloys to HEAs. For acidic ORR, the catalytic performance of SNRs improves as entropy increases, wherein the high‐entropy PtPdNiFeGa SNRs exhibit optimal catalytic activity and superior stability. Our theoretical investigations suggest that more bonding states are formed in the HEAs, which is conducive to creating new active sites with greater electron accumulation near the Fermi level for low‐barrier electron transfer, besides resulting in a denser crystal structure with robust catalytic stability. When equipped in the membrane electrode assembly, the PtPdNiFeGa SNRs deliver a remarkable mass activity (MA = 0.79 A/mg Pt at 0.9 V) and stability (MA retention = 82% after 30 000 cycles), outperforming most of the reported PtPd‐based catalysts.