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 Co_(9)S_(8) nanoflakes decorated Co_(3)O_(4) nanoarrays with enriched heterogeneous interface zones on Ni foam(Co_(9)S_(8)@CO_(3)O_(4)/NF)via a novel step-wise approach.The Co_(9)S_(8)@Co_(3)O_(4)/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.