Hollow nanocubes composed of well-dispersed mixed metal-rich phosphides in N-doped carbon as highly efficient and durable electrocatalysts for the oxygen evolution reaction at high current densities

The oxygen evolution reaction (OER) received a great deal of research attention in the past few years because of its prime role in electrocatalytic water splitting, rechargeable metal-air batteries, and fuel cells. To be competitively applicable at large scales, the electrocatalytic water-splitting system needs electrocatalysts that are cost effective, highly efficient, and highly durable. A novel metal-organic-framework (MOF)-derived and SiO ₂ -protected phosphorization approach was developed to prepare hollow nanocubes composed of well-dispersed Ni ₅ P ₄ /Fe ₃ P in N-doped carbon as cost-effective OER electrocatalysts, which are highly efficient and durable at high current density operations. Because of their unique structural and compositional features, the N-doped C/Ni ₅ P ₄ /Fe ₃ P hollow nanocubes not only achieved excellent electrocatalytic efficiencies (η ₁₀ = 252 mV and η ₂₅₀ = 385 mV), but also outstanding electrocatalytic activities with an ultralow Tafel slope of 24.0 mV dec ^-1 , the lowest ever reported to the best of our knowledge. More importantly, the N-doped C/Ni ₅ P ₄ /Fe ₃ P hollow nanocubes exhibited eminent long-term stability, both electrocatalytically and mechanically, even at a high current density of 250 mA cm ^-2 . These outstanding performances make the developed N-doped C/Ni ₅ P ₄ /Fe ₃ P hollow nanocubes a promising candidate to replace commercial noble metal oxide-based OER electrocatalysts for large-scale applications.