A Nanosized CoNi Hydroxide@Hydroxysulfide Core-Shell Heterostructure for Enhanced Oxygen Evolution.

A cost-effective and highly efficient oxygen evolution reaction (OER) electrocatalyst will be significant for the future energy scenario. The emergence of the core-shell heterostructure has invoked new feasibilities to inspire the full potential of non-precious-metal candidates. The shells always have a large thickness, affording robust mechanical properties under harsh reaction conditions, which limits the full exposure of active sites with highly intrinsic reactivity and extrinsic physicochemical characters for optimal performance. Herein, a nanosized CoNi hydroxide@hydroxysulfide core-shell heterostructure is fabricated via an ethanol-modified surface sulfurization method. Such a synthetic strategy is demonstrated to be effective in controllably fabricating a core-shell heterostructure with an ultrathin shell (4 nm) and favorable exposure of active sites, resulting in a moderately regulated electronic structure, remarkably facilitated charge transfer, fully exposed active sites, and a strongly coupled heterointerface for energy electrocatalysis. Consequently, the as-obtained hydroxide@hydroxysulfide core-shell is revealed as a superior OER catalyst, with a small overpotential of 274.0 mV required for 10.0 mA cm-2 , a low Tafel slope of 45.0 mV dec-1 , and a favorable long-term stability in 0.10 M KOH. This work affords fresh concepts and strategies for the design and fabrication of advanced core-shell heterostructures, and thus opens up new avenues for the targeted development of high-performance energy materials.