Multiple structural defects in ultrathin NiFe-LDH nanosheets synergistically and remarkably boost water oxidation reaction

Modifying electrocatalysts nanostructures and tuning their electronic properties through defects-oriented synthetic strategies are essential to improve the oxygen evolution reaction (OER) performance of electrocatalysts. Current synthetic strategies about electrocatalysts mainly target the single or double structural defects, while the researches about the synergistic effect of multiple structural defects are rare. In this work, the ultrathin NiFe layered double hydroxide nanosheets with a holey structure, oxygen vacancies and Ni³⁺ defects on nickel foam (NiFe-LDH-NSs/NF) are prepared by employing a simple and green H₂O₂-assisted etching method. The synergistic effect of the above three defects leads to the exposure of more active sites and significant improvement of the intrinsic activity. The optimized catalyst exhibits an excellent OER performance with an extraordinarily low overpotential of 170 mV at 10 mA·cm⁻² and a small Tafel slope of 39.3 mV·dec⁻¹ in 1 M KOH solution. Density functional theory calculations reveal this OER performance arises from pseudo re-oxidized metal-stable Ni³⁺ near oxygen vacancies (O_vac), which suppresses 3d-e_g of Ni-site and elevates d-band center towards the competitively low electron-transfer barrier. This work provides a new insight to fabricate advanced electrocatalysts for renewable energy conversion technologies.