Boosting the Oxygen Evolution Reaction Activity of NiFe₂O₄ Nanosheets by Phosphate Ion Functionalization

Here, we demonstrate an effective strategy to constitutionally increase the conductivity and electrocatalytic property of NiFe₂O₄ by phosphate ion functionalization. The phosphate-ion-modified NiFe₂O₄ (P-NiFe₂O₄) nanosheets are readily grown on a carbon cloth by a simple hydrothermal method and followed by a phosphating process. The introduction of phosphate ions on the NiFe₂O₄ surface is highly beneficial for increasing the charge transport rate and electrocatalytic active sites. As a result, the as-prepared P-NiFe₂O₄ nanosheets show outstanding electrocatalytic activity toward oxygen evolution reaction (OER), with a low overpotential (231 mV at 10 mA/cm²) and Tafel slope (49 mV/dec). Furthermore, the P-NiFe₂O₄ electrode has a remarkable stability with no activity fading after 50 h. In addition, the as-fabricated water electrocatalysts exhibit excellent flexibility at the foldable state. These features make the phosphate-ion-functionalized NiFe₂O₄ electrodes open a new way to develop OER electrocatalysts with high electrochemical property.