P-doped MOF-derived CoNi bimetallic sulfide electrocatalyst for highly-efficiency overall water splitting

Transition metal sulfides (TMSs) are widely used in energy storage and energy conversion systems because of their excellent electrochemical properties. However, their application is restricted by a low electron transfer efficiency, few active sites and poor stability. In this paper, CoNi bimetallic sulfides supported by carbon skeleton (CoNi-SP/NPC) were prepared using bimetallic organic frameworks (MOFs) as templates and modified with phosphorus doping. Compared with single metal sulfides, the bimetallic sulfides are more favorable for electron transfer in the catalytic process. Meanwhile, the carbon skeleton support gives the catalyst higher mechanical stability, and the P-doping brings more active sites into to contact with the aqueous solution. The overpotential of CoNi-SP/NPC catalyst is only 105 mV at 10 mA cm−2 for hydrogen evolution reaction (HER) and 313 mV at 100 mA cm−2 for oxygen evolution reaction (OER). In addition, CoNi-SP/NPC also displays remarkable performance in the course of overall water splitting, which can achieve 50 mA cm−2 at only 1.8 V and remains good stability for 12 h. This work proposes a feasible strategy to synthesize highly efficient water splitting electrocatalysts.