Hollow metal composite phosphides derived from MOFs as highly efficient and durable bifunctional electrocatalysts for water splitting

Abstract

Exploring efficient non-precious electrocatalysts with dual functionality for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solutions is critical and challenging. In this work, hollow Fe₂P@Ni₂P/Ni₅P₄ nanospindles were obtained by the co-deposition of Fe-MIL-88A in a Ni²⁺ ammonia solution and low-temperature phosphating treatment. The resulting hollow Fe₂P@Ni₂P/Ni₅P₄ nanospindles can serve as highly active and durable bifunctional electrocatalysts toward HER and OER in alkaline solutions. In particular, the as-prepared hollow Fe₂P@Ni₂P/Ni₅P₄ nanospindle exhibits excellent OER activity with a low overpotential of 230 mV to attain a current density of 10 mA cm⁻², a small Tafel slope of 18.2 mV dec⁻¹, and an excellent stability of 49 h continuous measurement. Moreover, the catalyst also displays a remarkable performance for HERs in 1 M KOH electrolyte with a overpotential of 376 mV to reach a current density of 20 mA cm⁻² and a superior long-term stability for 110 h. The hollow and porous structure of the Fe₂P@Ni₂P/Ni₅P₄ nanospindle can effectively promote the transfer of electrolytes and increase the number of electrocatalytic active sites.