Self-Assembly of Three-Dimensional Zinc-Doped NiCo₂ O₄ as Efficient Electrocatalysts for Oxygen Evolution Reaction

In this work, a series of three-dimensional porous flower-like zinc doped NiCo₂ O₄ (ZNCO) nanostructures with different Zn doping level are successfully prepared by a facile solvothermal process without using any templets. The obtained products are characterized by various techniques, and their electrocatalytic performances are also assessed by the oxygen evolution reaction (OER). According to the electrochemical characterization, it is demonstrated that ZNCO-0.15 (i.e., Zn_0.15 Ni_0.85 Co₂ O₄ ) nanoflowers show a lower overpotential, smaller Tafel slope, higher electrochemical active surface area (ECSA), as well as a larger turnover frequency (TOF) value than those of Co₃ O₄ , NiCo₂ O₄ , and ZnCo₂ O₄ nanoflowers, indicating that introduction of an optimal content of zinc ions plays an important role in enhancing electrocatalytic performances for OER. The enhanced OER performance of ZNCO-0.15 could be attributed to the increased number of active sites (Co³⁺ ), accelerated kinetic rate, and promoted conductivity of the catalyst with the incorporation of zinc ions.