High-Index-Faceted NiS Branch Arrays as Bifunctional Electrocatalysts for Efficient Water Splitting

For efficient electrolysis of water for hydrogen generation or other value-added chemicals, it is highly relevant to develop low-temperature synthesis of low-cost and high-efficiency metal sulfide electrocatalysts on a large scale. Herein, we construct a new core–branch array and binder-free electrode by growing NiS nanoflake branches on an atomic-layer-deposited (ALD) TiO skeleton. Through induced growth on the ALD-TiO backbone, cross-linked NiS nanoflake branches with exposed { 2 ¯ 10 } high-index facets are uniformly anchored to the preformed TiO core forming an integrated electrocatalyst. Such a core–branch array structure possesses large active surface area, uniform porous structure, and rich active sites of the exposed { 2 ¯ 10 } high-index facet in the NiS nanoflake. Accordingly, the TiO@NiS core/branch arrays exhibit remarkable electrocatalytic activities in an alkaline medium, with lower overpotentials for both oxygen evolution reaction (220 mV at 10 mA cm) and hydrogen evolution reaction (112 mV at 10 mA cm), which are better than those of other NiS counterparts. Stable overall water splitting based on this bifunctional electrolyzer is also demonstrated.[Figure not available: see fulltext.].