Trimetallic MOF‐74 Films Grown on Ni Foam as Bifunctional Electrocatalysts for Overall Water Splitting

Abstract Developing earth‐abundant and high‐performance electrocatalysts for water splitting has long been a vital research in energy conversion field. Herein, we report the preparation of a series of trimetallic uniform Mn x Fe y Ni‐MOF‐74 films in‐situ grown on nickel foam, which can be utilized as bifunctional electrocatalysts towards overall water splitting in alkaline media. The introduction of Mn can simultaneously regulate the morphology of MOF‐74 to form uniform film and modulate electronic structure of Fe to form more Fe(II)−O−Fe(III) motifs, which is conducive to the exposure of active sites and stabilizing high‐valent metal sites. The optimized Mn 0.52 Fe 0.71 Ni‐MOF‐74 film electrode showed excellent electrocatalytic performance, affording a current density of 10 mA ⋅ cm −2 at an overpotential of 99 mV for HER and 100 mA ⋅ cm −2 at an overpotential of 267 mV for OER, respectively. Assembled as an electrolyser, Mn 0.52 Fe 0.71 Ni‐MOF‐74 film electrode exhibited excellent performance towards overall water splitting, with ultralow overpotential of 245 and 462 mV to achieve current density of 10 and 100 mA ⋅ cm −2 , respectively. This work provides a new view to develop multi‐metal MOF‐based electrocatalysts.