Alternate Restacking of 2 D CoNi Hydroxide and Graphene Oxide Nanosheets for Energetic Oxygen Evolution

Morphology and composition tuning of layered materials is evaluated to influence their electrochemical performance for energy storage and conversion applications. Layered Co_1-x Ni_x hydroxides (x=0, 1/2, 1/3, 1/4, 1) of three different morphologies-nanocones, 2 D nanosheets obtained by the rapid exfoliation of nanoconical counterparts, and 2 D superlattice-like nanostructures alternately restacked by the oppositely charged hydroxide and graphene oxide (GO) nanosheets-have been systematically investigated for electrocatalytic oxygen oxidation. High activity is obtained with the 2 D Co_2/3 Ni_1/3 hydroxide nanosheets/GO superlattice (Co_2/3 Ni_1/3 NS-GO), achieving a current density of 10 mA cm^-2 at a low overpotential of 259 mV accompanied by a small Tafel slope of 35.7 mV dec^-1 , surpassing nanocones and 2 D nanosheets, as well as the congeneric heterostructured Co_1-x Ni_x hydroxide nanosheets/GO nanoarchitectures (Co_1-x Ni_x NS-GO; x=0, 1/2, 1/4, 1) and the commercial RuO₂ electrocatalyst. The outstanding activity of Co_2/3 Ni_1/3 NS-GO superlattice uncovers the combined merits of 2 D superlattice-like structure and composition optimization for electrocatalysis, providing a strategy for developing high-performance electrochemical materials by rational morphology and composition design.