Tuning Unique Peapod‐Like Co(SxSe1–x)2 Nanoparticles for Efficient Overall Water Splitting

The development of efficient electrocatalysts with low cost and earth abundance for overall water splitting is very important in energy conversion. Although many electrocatalysts based on transition metal dichalcogenides have been developed, rational design and controllable synthesis of fine nanostructures with subtle morphologies and sequential chemical compositions related to these materials remains a challenge. This study reports a series of peapod-like composites with component-controllable Co(SxSe1–x)2 nanoparticles encapsulated in carbon fibers, which are obtained by using Co(CO3)0.5(OH)·0.11H2O nanowires as a precursor followed by coating carbon fiber and an adjustable sulfuration/selenylation process. Due to its increased exposure of active sites and improved charge and mass transport capability derived from the unique structure and morphology, the Co(SxSe1–x)2 samples display favorable catalytic activities. It is found that Co(S0.71Se0.29)2 exhibits the best hydrogen evolution reaction (HER) performance and Co(S0.22Se0.78)2 shows the highest activity for the oxygen evolution reaction (OER). When using Co(S0.71Se0.29)2 as a cathode and Co(S0.22Se0.78)2 as an anode, it demonstrates a durable activity for overall water splitting to deliver 10 mA cm−2 at a cell voltage of 1.63 V, thus offering an attractive cost-effective earth abundant material system toward water splitting.