Twinning Strain‐Induced Pathway Switching on PtPdRuFe Nanoflowers Enables Efficient Formic Acid Oxidation

ABSTRACT Challenges in regulating formic acid oxidation reaction (FAOR) pathways have primarily compromised the output performance of direct formic acid fuel cells (DFAFCs). Herein, we leverage twin boundaries (TBs) engineering in PtPdRuFe nanoflowers (NFs) to deliberately steer the FAOR predominantly along the non‐CO dehydrogenation pathway. The introduced TBs induce localized tensile strain, effectively modulating the d ‐orbital electronic structure across all constituent metals, which is crucial for redirecting the formation of transition‐state intermediates. Specifically, a stronger adsorption affinity for HCOO * over COOH * on Pt and Fe sites is achieved, which reverses the situation that on the non‐twin PtPdRuFe counterpart and thereby preferentially prompts FAOR via a desirable dehydrogenation pathway. Concurrently, the conversion of CO * is also accelerated due to the enhanced adsorption of OH * on Ru/Fe sites, further eliminating the poisoning and deactivation issues induced by CO * . Profiting by these synergistic enhancements, the as‐fabricated twin‐PtPdRuFe NFs demonstrate markedly improved catalytic activity and durability, outperforming the non‐twin counterpart and benchmark Pt/C, enabling them to be among one of the best‐performing acid‐stable FAOR catalysts.