Cation defect engineering of core–shell spinels nanoelectrocatalyst for enhanced oxygen evolution reaction.

Defect engineering is a promising approach to address the inherently low conductivity and limited number of reaction sites of manganese-based spinel oxides as electrocatalysts. However, high formation energies make it challenging to controllably generate cation defects in such spinel oxides. Herein, we report a heterogeneous core–shell electrocatalyst [Mn₃O₄@Mn_xCo_3−xO₄–Co₂(OH)₃Cl, MCIL] based on a facile cation-deficiency strategy. The addition of ionic liquid (1-butyl-3-methylimidazole hexafluorophosphate) to the reaction system can simply and quickly control the octahedral field defects in spinel MnCo₂O₄. The results show that the selective generation of defects in the Co(O_h) octahedral field can accelerate the OER reaction kinetics and provide excellent OER electrocatalytic performance. Specifically, the MCIL series catalysts can exhibit the lowest overpotential of 332 mV at 10 mA cm⁻² and Tafel slope of 50 mV dec⁻¹, compared with that of pristine samples [i.e., Mn₃O₄ (890 and 343 mV dec⁻¹) and Mn₃O₄@MnCo₂O₄ (357 and 56 mV dec⁻¹)]. This work highlights the importance of cation defect engineering to enhance the catalytic activity of materials. [ABSTRACT FROM AUTHOR]