Heterostructuring Mesoporous 2D Iridium Nanosheets with Amorphous Nickel Boron Oxide Layers to Improve Electrolytic Water Splitting.

2D heterostructures exhibit a considerable potential in electrolytic water splitting due to their high specific surface areas, tunable electronic properties, and diverse hybrid compositions. However, the fabrication of well-defined 2D mesoporous amorphous-crystalline heterostructures with highly active heterointerfaces remains challenging. Herein, an efficient 2D heterostructure consisting of amorphous nickel boron oxide (Ni-B i ) and crystalline mesoporous iridium (meso-Ir) is designed for water splitting, referred to as Ni-B i /meso-Ir. Benefiting from well-defined 2D heterostructures and strong interfacial coupling, the resulting mesoporous dual-phase Ni-B i /meso-Ir possesses abundant catalytically active heterointerfaces and boosts the exposure of active sites, compared to their crystalline and amorphous mono-counterparts. The electronic state of the iridium sites is tuned favorably by hybridizing with Ni-B i layers. Consequently, the Ni-B i /meso-Ir heterostructures show superior and stable electrochemical performance toward both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline electrolyte.