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 (NixCo1-x(CO3)(0.5)OH). 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.