Balancing Activity and Stability in Spinel Cobalt Oxides through Geometrical Sites Occupation towards Efficient Electrocatalytic Oxygen Evolution

Abstract Designing active and stable oxygen evolution reaction (OER) catalysts are vitally important to various energy conversion devices. Herein, we introduce elements Ni and Mn into (Co) tet (Co 2 ) oct O 4 nanosheets (NSs) at fixed geometrical sites, including Mn oct , Ni oct , and Ni tet , to optimize the initial geometrical structure and modulate the CoCo 2 O 4 surface from oxygen‐excess to oxygen‐deficiency. The pristine (Ni,Mn)‐(Co) tet (Co 2 ) oct O 4 NSs shows excellent OER activity with an overpotential of 281.6 mV at a current density of 10 mA cm −2 . Moreover, without damaging their initial activity, the activated (Act)‐(Ni,Mn)‐(Co) tet (Co 2 ) oct O 4 NSs after surface reconstruction exhibit long‐term stability of 100 h under 10 mA cm −2 , 50 mA cm −2 , or even 100 mA cm −2 . The optimal balance between electroactivity and stability leads to remarkable OER performances, providing a pivotal guideline for designing ideal electrocatalysts and inspiring more works to focus on the dynamic change of each occupation site component.