Mo-doping-assisted electrochemical transformation to generate CoFe LDH as the highly efficient electrocatalyst for overall water splitting

Facile preparation of efficient, low-cost, and stable bifunctional electrocatalysts for overall water splitting remains a big challenge. Herein, we successfully synthesized Mo-doped CoFe layered double hydroxides (Mo-doped CoFe LDH/NF) nanosheets by electrochemical transformation of Mo-doped CoFe prussian blue nanocubes on nickel foam (Mo-doped CoFe PBA/NF) for highly efficient overall water splitting. The catalyst exhibits outstanding oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance after electrochemical transformation, which is due to the abundant edge defects of Mo-doped CoFe LDH/NF can expose more active sites. Meanwhile, Mo6+ has a strong electron absorption ability, which could adjust the electronic structure and stabilize the high valence active sites. It only requires a low overpotential for OER (331 mV) and HER (227 mV) to reach 100 mA cm−2 in alkaline media, respectively. Notably, when it was employed as a bifunctional electrode, Mo-doped CoFe LDH/NF displays a low potential of 1.55 V to reach 100 mA cm−2 coupled with long-term water splitting stability in an alkaline electrolyte. This work not only developed a novel method for the synthesis of efficient double-layer hydroxide catalysts, but also paved the way for the rational design of bifunctional electrocatalysts with practical application value.