The NHx Group Induced Formation of 3D α-Co(OH)2 Curly Nanosheet Aggregates as Efficient Oxygen Evolution Electrocatalysts.

Recently, the curly structure attracts researchers' attention due to the strain effect, electronic effect, and improved surface area, which exhibits enhanced electrocatalytic activity. However, the synthesis of metastable curved structures is very difficult. Herein, a simple room temperature coprecipitation method is proposed to synthesize 3D cobalt (Co) hydroxide (α-Co(OH)2 ) electrocatalysts that consist of curly 2D nanosheets. The formation process of curly nanosheets is elaborated systematically and the results demonstrate that the NHx group has great effect on the formation of curly structure. Combining the advantage of 2D curly nanosheet and 3D aggregate structure, the as-prepared α-Co(OH)2 curly nanosheet aggregates show the best water oxidation activity with an overpotential of 269 mV at j = 10 mA cm-2 in 1.0 m KOH. The electrocatalytic process studies demonstrate that the formation of CoIV O species is the rate-determining step. Theoretical calculations further confirm the beneficial effect of the bent structure on the conductivity, the adsorption of OH- and the formation of OOH* species.