Controllable structure reconstruction of nickel–iron compounds toward highly efficient oxygen evolution

. Our findings demonstrate that the composition of Ni-Fe compounds influences the oxidizing ability of Ni and consequently their catalytic performance. We also reveal a strong correlation between the structure and oxidizing power of the Ni in Ni-Fe compounds and their OER activity, indicating that the well-engineered structure and Ni-site electronics are the primary origins of their OER activity. This work not only provides a promising guideline for the design and synthesis of Ni/Fe based compounds, but also highlights the crucial role of each component in enhancing the activity of these electrocatalysts.