Foam–like Co₉S₈/Ni₃S₂ heterostructure nanowire arrays for efficient bifunctional overall water–splitting

Foam–like nanowire arrays composed of the Co₉S₈/Ni₃S₂ heterostructure possess huge electrochemical surface areas and rich lattice defects. The value of double–layer capacitance for Co₉S₈/Ni₃S₂ is detected to be 81.4 m F·cm⁻², which is four times more than the precursor (Ni_xCo_1-x(CO₃)_0.5OH). This enhancement greatly produces a large number of catalytic reaction sites for contacting with electrolyte ions. The method of in–situ vulcanization growth urges the uniform distribution of Co₉S₈ and Ni₃S₂, forming a large number of lattice defects in the heterointerfaces. These lattice defects modulate the local electronic arrangement to become the most active reaction sites. Density functional theory calculations demonstrate that the defective heterointerfaces are beneficial to the chemisorption of H⁺ and OH–. Electrochemical tests illustrate that Co₉S₈/Ni₃S₂ electrodes exhibit efficient activities for oxygen and hydrogen evolution reactions and have remarkable stabilities in alkaline solution for commercial application.