Exploring the evolution of active sites on <scp> Fe ₂ GeO ₄ </scp> – <scp> Ni ₃ Ge ₂ O ₅ </scp> ( <scp>OH</scp> ) ₄ interfaces for water oxidation

Abstract The oxygen evolution reaction (OER) is a pivotal process in electrochemical energy conversion. Herein, we report a computational study‐guided experimental work that uncovers the dynamics of active sites in a heterostructure composed of two distinct phases: Brunogeierite (Fe 2 GeO 4 ) and serpentine (Ni 3 Ge 2 O 5 (OH) 4 ). This heterostructure is synthesized by introducing varying amounts of a nickel precursor into pristine Fe 2 GeO 4 . When comparing pristine materials, Fe in Fe 2 GeO 4 is better for OER as compared with the Ni in Ni 3 Ge 2 O 5 (OH) 4 . Interestingly, the Ni becomes more active in the heterostructure following the structural distortion and the induced increased electron transfer, which we proved by ex situ/in situ XAS studies. These findings highlight the dynamic evolution of active sites in the heterostructure, elucidating how the synergy between structural and electronic factors transforms catalytic behavior. The optimized heterostructure as an ideal model reveals enhanced electrocatalytic performance with an overpotential of 325 mV versus RHE to achieve a current density of 100 mA cm – 2 , a Tafel slope of 42 mV dec –1 , and long‐term stability exceeding 50 h even at high current densities, making it highly promising for a wide range of critical electrolysis applications. image