Ultralow iridium loading with three-layer core/shell structured IrFe@Fe 3 O 4 @NiFe LDH as efficient bifunctional electrocatalysts for overall water splitting

Highly active electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are crucial for efficient hydrogen production. In this work, a three-layer structured bifunctional electrocatalyst with an ultralow Ir loading of ~ 0.61% is fabricated for overall water splitting through a green and scalable two-step wet chemistry method. In the three-layer core–shell structure, the inner IrFe bimetallic alloy and the outer NiFe layered double hydroxides (LDH) mainly account for the HER and OER activity origin, respectively. Benefit from the unique structure and its synergistic effect among the two kinds of active sites, IrFe@Fe 3 O 4 @NiFe LDH bifunctional electrocatalysts only require an overpotential of 146 and 227 mV to deliver 100 mA cm −2 for HER and OER, respectively. In addition, only 1.46 V of cell voltage is required to reach a current density of 10 mA cm −2 for overall water splitting and it can continuously steadily work for 770 h at 500 mA cm −2 . This work provides a facile and green strategy to design low load noble metal based electrocatalysts for efficient and stable overall water splitting at large current densities.