High-Index-Faceted Ni₃S₂ 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 Ni₃S₂ nanoflake branches on an atomic-layer-deposited (ALD) TiO₂ skeleton. Through induced growth on the ALD-TiO₂ backbone, cross-linked Ni₃S₂ nanoflake branches with exposed { 2 ¯ 10 } high-index facets are uniformly anchored to the preformed TiO₂ 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 Ni₃S₂ nanoflake. Accordingly, the TiO₂@Ni₃S₂ 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 Ni₃S₂ counterparts. Stable overall water splitting based on this bifunctional electrolyzer is also demonstrated.[Figure not available: see fulltext.].