High-Index-Faceted Ni(3)S(2) 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 Ni(3)S(2) nanoflake branches on an atomic-layer-deposited (ALD) TiO(2) skeleton. Through induced growth on the ALD-TiO(2) backbone, cross-linked Ni(3)S(2) nanoflake branches with exposed {[Formula: see text] } high-index facets are uniformly anchored to the preformed TiO(2) 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 {[Formula: see text] } high-index facet in the Ni(3)S(2) nanoflake. Accordingly, the TiO(2)@Ni(3)S(2) 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(−2)) and hydrogen evolution reaction (112 mV at 10 mA cm(−2)), which are better than those of other Ni(3)S(2) counterparts. Stable overall water splitting based on this bifunctional electrolyzer is also demonstrated. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40820-019-0242-8) contains supplementary material, which is available to authorized users.