Modulated transition metal–oxygen covalency in the octahedral sites of CoFe layered double hydroxides with vanadium doping leading to highly efficient electrocatalysts

Abstract

The development of efficient and stable non-noble-metal electrocatalytic materials for the oxygen evolution reaction (OER) is a huge and important challenge at present. Herein, we report the prominent enhancement of OER activity via doping vanadium into CoFe-based layered double hydroxide (LDH) electrocatalysts. Electrochemical characterization shows that the Co₂Fe_0.5V_0.5 LDH grown on carbon papers (CPs) has an enormous electrochemical surface area (ECSA) and exhibits the smallest overpotential of 242 mV at 10 mA cm⁻², which only requires a small Tafel slope of 41.4 mV dec⁻¹ in 1 M KOH solution. The X-ray photoelectron spectroscopy (XPS) peak position of Co, Fe and O moves slightly to higher binding energy, elucidating the improved covalency of the metal–oxygen bond after V doping. DFT+U simulation indicates that the outstanding electrocatalytic activity of Co₂Fe_0.5V_0.5 could be ascribed to the increased metal–oxygen covalency in LDH after V element doping, and facilitates the charge-transfer from oxygen to the metal. This finely tuned strategy by V doping into the CoFe-based LDH matrix can adjust the covalency of metal–oxygen bridges and enhance its electrocatalytic activity for the OER. In this work, we also present a general method to study various highly efficient metal hydroxide catalysts for the OER.