Dual-path Fe migration in the bulk phase reconstructing high quality Ni-O-Fe units for high efficient oxygen evolution reaction

In the oxygen evolution reaction (OER), the non-reversible destruction of surface electronic structure caused by the irregular element migration in complex surface/interface reaction limits the improvement of catalyst's activity and stability. Herein, we successfully realize the control of 'dual-path migration of metallic elements in OER' to stepwise reconstruct the O-coordinated bi-metal heterodimer (M1-O-M2) for electron density redistribution. By designing Fe@FeNi3@NiO-Fe3O4 (F-FN-NFO) model electrode with stepwise surface treatment in OER process, the directional migration (from core to shell, path 1) and adjacent-surface migration of Fe atoms (path 2) are both controlled to reduce the formation energy of Ni-O-Fe units, realizing strengthened electron transfer between heterogeneous metal centers. After the surface reconstruction, the OER activity of F-FN-NFO increases for 8.6 times at 1.7 V (30.5-263 mA cm-2). Based on this strategy, the designed three-dimension NiFe@NiFexO is positive activated compared to traditional NiFe-oxidation with the overpotential reduced to 299 mV at 10 mA cm-2.