In situ carbon-encapsulated CoS2/Zn0.76Co0.24S composite derived from intercalated CoZn-layered double hydroxide precursor for overall water splitting

The exploration of highly active and stable bifunctional catalysts based on structural adjustment and charge redistribution is imperative toward overall water splitting. The graphitized carbon encapsulation and the introduction of zinc atoms could enhance conductivity and optimize the electronic structure of catalysts, thereby improving the activities of the oxygen and hydrogen evolution reactions (OER and HER). Herein, a carbon-encapsulated CoS 2 and Zn 0.76 Co 0.24 S composite with porous structure (CoS 2 /Zn 0.76 Co 0.24 S@C) is constructed for overall water splitting by sulphurating a precursor of metanilic guest-intercalated Co Zn-layered double hydroxide (CoZn-LDH) host. Consequently, CoS 2 /Zn 0.76 Co 0.24 S@C reveals lower overpotentials of 260 and 152 mV at 10 mA·cm −2 for OER and HER, respectively, outperforming those of CoS 2 , CoS 2 @C and CoS 2 /ZnS. For overall water splitting, a CoS 2 /Zn 0.76 Co 0.24 S@C-based electrolysis cell exhibits a low cell voltage of 1.66 V at 10 mA·cm −2 with a retention of 81% after 40 h, indicating satisfactory stability. Density functional theory calculations further demonstrate that the encapsulated carbon layer could tune the d-band center of CoS 2 and Zn 0.76 Co 0.24 S. The cooperation of cobalt sulfide with zinc atoms could reduce the work function and promote electronic redistribution, thus enhancing conductivity and boosting the OER/HER kinetics of the catalyst. This work provides an effective strategy for obtaining high conductivity, acceptable activity, strong stability and cost-effective electrocatalysts for water splitting.