Chlorine-assisted synthesis of CuCo2S4@(Cu,Co)2Cl(OH)3 heterostructures with an efficient nanointerface for electrocatalytic oxygen evolution

[Display omitted] The demand for sustainable energy sources urges the development of efficient and earth-abundant electrocatalysts. Herein, chlorine assisted ion-exchange and in-situ sulfurization processes were combined to construct CuCo2S4@(Cu,Co)2Cl(OH)3 heterostructures from Cu(OH)2 nanoarrays. Chlorine element in the cobalt source stimulated the formation of (Cu,Co)2Cl(OH)3 precursor, and further facilitated partial transformation of the precursor to CuCo2S4 on the surface to achieve composite structure. The mixed valences of Co element (Co3+ in CuCo2S4 and Co2+ in (Cu,Co)2Cl(OH)3) and OS interpenetrated nanointerface in the composite catalysts provided low electron transfer resistance for good alkaline oxygen evolution reaction (OER) activities. In 1 mol L−1 KOH electrolyte, the overpotentials of the optimal composite catalyst reached 253 and 290 mV respectively at the current density of 20 and 50 mA cm−2, which is comparable to the activity of commercial Ir/C (281 mV@20 mA cm−2). These findings could provide opportunities for designing effective and inexpensive composite electrocatalysts through nanointerface engineering strategy.