Lattice strain Improves activity and stability of asymmetric Ag₁₁Pd₁₉Ir₈ nanodendrites by pre-deposition and galvanic replacement reaction

Enhancing catalyst activity and stability involves understanding mechanisms like ligand effects, ensemble effects, and strain effects. Notably, strain effects from surface defects, such as dislocations or grain boundaries, play a crucial role by complementing ligand effects and resisting surface restructuring during catalysis. However, the precise mechanism by which strain and grain boundaries enhance catalytic activity and stability remains unclear. This study unveils it through a novel strategy: pre-preparing nickel dendrites and galvanically reducing them to form micro-strained Ag₁₁Pd₁₉Ir₈ nanodendrites, effective for formate oxidation and hydrogen production. TEM analysis shows these nanodendrites contain asymmetric nanocrystals with stacking faults, causing micro-strains. Electrochemical tests reveal Ag₁₁Pd₁₉Ir₈ nanodendrites have 6.9 times higher mass activity than Pd nanodendrites and retain 460 mA mgPd⁻¹ activity after 3600 s, 38 times greater than Pd nanodendrites. They also exhibit exceptional hydrogen production with a TOF of 470.8 h⁻¹, 12.7 times higher than Pd nanodendrites, maintaining robust activity upon reuse. Theoretical studies indicate minimized energy-limiting steps for formate oxidation and dehydrogenation, enhancing performance over Ag₁₅Pd₁₉Ir₄ and Ag₈Pd₁₉Ir₁₁ nanodendrites. This work provides a novel approach for developing durable, high-performance anode catalysts for direct formate fuel cells and hydrogen production.