Mo-doped Co3O4 ultrathin nanosheet arrays anchored on nickel foam as a bi-functional electrode for supercapacitor and overall water splitting

Simple preparation, favorable price and environmental protection have been a long-term challenge in the field of electrochemistry. Herein, we studied and prepared a bifunctional Mo-doped Co3O4 ultrathin nanosheets, which has been validated as an effective binder-free electrode material for electrocatalytic water splitting and supercapacitors. The material has a large specific surface area, high electrical conductivity and exposure to more active sites, breaking down the limited performance and range of use of transition metal oxides. Benefiting from intriguing ultrathin property and conductivity, OER and HER process of 0.4Mo-Co3O4 have a small Tafel slope of 83.7 and 98 mV dec−1, respectively. The current density at 10 mA cm−2 show a low overpotential of 315 and 79 mV and significant stability. The water electrolytic device requires a potential of 1.64 V to reach 10 mA cm−2, and the potential change is negligible after 12 h of continuous electrolysis. In addition, the manifest improved electrochemical performance of 0.3Mo-Co3O4 as supercapacitor electrode material shows high areal capacitance 2815 mF cm−2 at 1 mA cm−2, excellent rate performance (85% at 10 mA cm−2) and retains 90% of the initial capacitance by cycling 5000 at a current density of 10 mA cm−2. Moreover, 0.3Mo-Co3O4||0.3Mo-Co3O4 symmetrical supercapacitor has a maximum volumetric energy density of 1.25 mW h cm−3 at a power density of 7.1 mW cm−3 and superior cycle life. The influence of doping on electrochemical performance was studied by changing the content of doped metal ions, which is of great significance for the exploration of supercapacitor and electrocatalytic hydrolysis of bifunctional electrode materials.