A self-supported bifunctional MoNi₄ framework with iron doping for ultra-efficient water splitting

Exploring highly efficient and durable bifunctional catalysts for enhancing overall water splitting (OWS) is greatly desired but challenging for electrocatalysis applications. Herein, Fe doping in three-dimensional (3D) tremella-like MoNi₄ alloy crystal frameworks (denoted as MNF_n CFs) is utilized for building up a bifunctional OWS electrocatalyst. Experimental analysis and density functional theory (DFT) simulations reveal that Fe doping enhances the conductivity, lowers the free energy barriers for water splitting, and weakens the adsorption of catalytic intermediates. In particular, a MNF_2.5 CF catalyst exhibits a superior OER performance, and requires an ultra-low overpotential of 187.18 mV to drive 30 mA cm⁻² and a low Tafel slope of 56.50 mV dec⁻¹ in 1 M KOH. Eventually, an OWS device consisting of MNF_2.5 CFs crystallized at 500 and 600 °C (MNF_2.5-500‖MNF_2.5-600 CFs) is demonstrated and can be driven by a 1.5 V AAA battery.