Low-electronegativity vanadium substitution in cobalt carbide induced enhanced electron transfer for efficient overall water splitting

Developing highly efficient electrocatalysts while revealing the active site and the reaction mechanism is essential for electrocatalytic water splitting. To overcome the number and location limitations of defects in electrocatalyst induced by conventional transition-metal atom (e.g. Fe, Co, Ni) surface doping, we report a facile strategy of substitution with lower electronegative vanadium in the cobalt carbide, leading to larger amounts of defects in the whole lattice. The self-supported and quantitatively substituted VxCo3-xC (0 ≤ x ≤0.80) were one-step synthesized in the electrospun carbon nanofibers (CNFs) through the solid-state reaction. Particularly, the V0.28Co2.72C/CNFs exhibits superior HER and OER activity, and delivers a current density of 10 mA cm-2 at 1.47 V as the alkaline electrolyzer, which is lower than the values for Pt/C–Ir/C couple (1.60 V). The Operando Raman spectra and DFT calculations show that the enhanced electron transfer from V to the orbit of the Co atom makes Co a local nega...