Abstract
In foam–like Co9S8/Ni3S2 nanowire arrays, the coexistence of two phases produce a lot of lattice defects, which modulate the electronic arrangement to reduce the chemisorption free energies of H+ and OH−. Meanwhile, foam–like structure provided fast electron conduction paths and large number of active sites for contacting with electrolyte ions to promote the electrochemical reactions.
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•Defect-enriching foam–like Co9S8/Ni3S2 nanowire arrays were successfully prepared.•In situ vulcanization treatment greatly increased the ECSA of heterostructure.•Lattice defects were more conducive to the chemisorption of H+ and OH–.•DFT calculations confirmed the low ΔGH and ΔGOH of the heterointerfaces.•Co9S8/Ni3S2 electrodes exhibited low η10 of 227 mV and η-10 of −128 mV.
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)0.5OH). 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.