A nanoflower-like polypyrrole-based cobalt-nickel sulfide hybrid heterostructures with electrons migration to boost overall water splitting

The development of high-efficiency and cost-effective difunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are highly attractive to fulfill the practical water electrolysis. Herein, a novel low-cost difunctional cobalt-nickel sulfide (Co3S4/Ni3S2) flower-like heterostructures are purposely loaded on the surface of polypyrrole (PPy) nanosheets on nickel foam (NF) via feasible and efficient electrodeposition and hydrothermal tactics. The unique hierarchical architecture of the PPy nanosheets and strong electron interaction in the Co3S4/Ni3S2 nanohybrid effectively offer sufficient specific surface area and regulate electronic configuration for expediting the electrocatalytic process. The theoretical simulations also provide convincing proof that the interface of the Co3S4/Ni3S2 heterostructures supplies a lower energy pathway for water adsorption and dissociation, and the electrons migration that occurs when heterostructures emerge is probably the root of the result above. Consequently, the as-fabricated Co3S4/Ni3S2@PPy/NF exhibits outstanding electrochemical activity of HER and OER requiring low overpotentials of 63 mV and 207 mV to reach a current density of 10 mA cm-2 in the alkaline electrolyte, respectively. When equipped in a two-electrode electrolyzer, the Co3S4/Ni3S2@PPy/NF electrode couple displays a low voltage of only 1.52 V at 10 mA cm-2, indicating its potential application in the field of the water electrolysis.