Tuning the electronic structure and inverse degree of inverse spinel ferrites by integrating samarium orthoferrite for efficient water oxidation

Optimized electronic configuration is of critical importance for developing active multimetallic electrocatalysts for oxygen evolution reaction (OER) but remains a challenge. Herein, we report a defect-rich samarium orthoferrite interfaced with samarium-doped nickel ferrite (SFO/Sm-NFO) as an efficient OER electrocatalyst. By multiple in situ ion-exchanges and calcination processes, the inverse degree and defects of SFO/Sm-NFO are effectively regulated to modulate the electronic structure at the interface. Our experimental and theoretical studies show that the Sm doping in NFO inverse spinels facilitates the rearrangement of Ni atoms to the octahedral sites that are the active site for OER. This enables highly enhanced OER activity as manifested by a low overpotential of 228 mV at 10 mA cm⁻² (Tafel slope = 38.6 mV dec⁻¹) with excellent stability at 500 and 1000 mA cm⁻² for 100 h. This work provides useful insights into the rational designing of multimetallic nanohybrids for active and practical electrocatalysts.