Engineering cobalt sulfide/oxide heterostructure with atomically mixed interfaces for synergistic electrocatalytic water splitting

It remains challenging to develop economical and bifunctional electrocatalysts toward oxygen/hydrogen evolution reactions (OER/HER). Herein, we construct Co9S8 nanoflakes decorated Co3O4 nanoarrays with enriched heterogeneous interface zones on Ni foam (Co9S8@Co3O4/NF) via a novel step-wise approach. The Co9S8@Co3O4/NF hybrid manifests excellent performance with low overpotentials of 130 mV for HER (10 mA·cm−2) and 331 mV for OER (100 mA·cm−2), delivering a small voltage of 1.52 V for water splitting at 10 mA·cm−2 as well as outstanding catalytic durability, which surpasses precious metals and previously reported earth-abundant nanocatalysts. Further experimental and theoretical investigations demonstrate that the excellent performance is attributed to the followings: (i) Highly conductive Ni facilitates the efficient charge transfer; (ii) porous core-shell nanoarchitecture benefits the infiltration and transportation of gases/ions; (iii) heterogeneous interface zones synergistically lower the chemisorption energy of hydrogen/oxygen intermediates. This work will shed light on the controllable synthesis and engineering of heterostructure nanomaterials for clean energy storage and conversion technologies.