Core-Shell Structured NiFeSn@NiFe (Oxy)Hydroxide Nanospheres from an Electrochemical Strategy for Electrocatalytic Oxygen Evolution Reaction.

Efficient electrocatalysts for the oxygen evolution reaction (OER) are highly desirable because of the intrinsically sluggish kinetics of OER. Herein, core-shell structured nanospheres of NiFe Sn@NiFe (oxy)hydroxide (denoted as NiFe Sn-A) are prepared as active OER catalysts by a facile electrochemical strategy, which includes electrodeposition of NiFe Sn alloy nanospheres on carbon cloth (CC) and following anodization. The alloy core of NiFe Sn could promote charge transfer, and the amorphous shell of NiFe (oxy)hydroxide is defect-rich and nanoporous due to the selective electrochemical etching of Sn in alkaline medium. The optimized catalyst of NiFeSn-A displays a remarkable OER performance with a low overpotential of 260 mV to reach the current density of 10 mA cm, a small Tafel slope of 50 mV dec, a high turnover frequency of 0.194 s at an overpotential of 300 mV, and a robust durability. Further characterizations indicate that the superior OER performance of the core-shell structured NiFeSn-A nanospheres might originate from abundant active sites and small charge transfer resistance. This work brings a new perspective to the design and synthesis of core-shell structured nanospheres for electrocatalysis through a facile electrochemical strategy.