Multiscale structural optimization: Highly efficient hollow iron-doped metal sulfide heterostructures as bifunctional electrocatalysts for water splitting

Hollow iron-doped Co-Mo sulfide (H-Fe-CoMoS) heterostructures with a highly efficient water-splitting catalytic ability were achieved by applying a multiscale optimization strategy. Morphological and compositional optimization on a macroscale achieved by assembling a bimetallic Co-Mo sulfide (CoMoS) heterostructure in a hollow-structured composite (H-CoMoS) gave the electrocatalyst an ability to conduct enhanced bifunctional activities for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Intrinsic electronic structure optimization on a microscale achieved by introducing a small amount of iron (Fe) into H-CoMoS (H-Fe-CoMoS) further improved its catalytic activity and stability. Electrochemical measurements revealed that this multiscale structural optimization promoted enhanced electrical conductivity and increased the number of electrochemical active sites on the H-Fe-CoMoS, leading to its remarkable electrocatalytic performance as a bifunctional catalyst for both HER and OER in alkaline media. The H-Fe-CoMoS showed overpotentials of 282 mV and 137 mV to achieve a current density of 10 mA cm(-2) for OER and HER, respectively, which are comparable to the performance of the benchmark OER catalyst RuO2 and HER catalyst Pt/C.