Vanadium-doped cobalt selenide: an efficient bifunctional electrocatalyst for overall water splitting

Abstract

To obtain catalysts with remarkable activity for overall water splitting, the rational design and synthesis of doped catalysts with rich active sites are paramount. Herein, we report the synthesis of a series of vanadium-doped cobalt selenides (V@CoSe₂-1, V@CoSe₂-2, and V@CoSe₂-3) by varying the composition of Co and V. Among the synthesized materials, V@CoSe₂-1 (with a Co to V molar ratio of 3 : 1) exhibited excellent performance towards the oxygen evolution reaction (OER). V@CoSe₂-1 facilitated the sluggish kinetics of the OER mechanism, leading to a low overpotential value of 310 mV at a current density of 10 mA cm⁻² and a low Tafel slope of 51.56 mV dec⁻¹. The efficiency of this electrocatalyst can be attributed to V doping, which led to an enhancement in the number of electroactive sites for the OER process. This electrocatalyst showed 16 hours stability at a current density of 10 mA cm⁻², enhancing its practical durability as an effective catalyst for the anodic OER in the water electrolysis process. Furthermore, V@CoSe₂-1 showed good hydrogen evolution reaction (HER) activity in an alkaline medium, showing an overpotential value of 212 mV at a current density of 10 mA cm⁻², Tafel slope of 94.49 mV dec⁻¹, and good stability for 40 hours in a harsh environment. Thus, V@CoSe₂-1 was employed as a bifunctional electrocatalyst for alkaline water splitting, requiring a cell voltage of 1.96 V at a current density of 10 mA cm⁻² and demonstrating exceptional stability for over 24 hours.