ZIF67@MoO₃ NSs@NF composite electrocatalysts reinforced by chemical bonds and oxygen vacancy for efficient oxygen evolution reaction and overall water-splitting

A kind of composite electrocatalysts with the structure of MoO₃ nanosheets coated by ZIF67 nanocrystals and grown on the nickel foam substrate (ZIF67@MoO₃ NSs@NF) is prepared and mainly used as the electrode for oxygen evolution reaction (OER) and overall water splitting. The excellent electrocatalytic activity of ZIF67@MoO₃ NSs@NF are demonstrated. It can use the overpotential (ƞ) of 178 mV and 386 mV respectively to drive 10 mA cm⁻² and 50 mA cm⁻². It is also observed that the ZIF67@MoO₃ NSs@NF electrode has the highest initial current density (45.7 mA cm⁻²) at 1.618 V and can maintain more than 90% of the initial current density after 20,000 s. The ZIF67@MoO₃ NSs@NF electrode also shows the small HER overpotential of 135 mV at 10 mA cm⁻². Furthermore, the voltage of ZIF67@MoO₃ NSs@NF as a bifunctional overall water splitting catalysts is 1.58 V at 10 mA cm⁻², which is superior to another noble metal electric catalyst combination RuO₂/NF(+)//Pt–C/NF(−). And the ZIF67@MoO₃ NSs@NF(+)//ZIF67@MoO₃ NSs@NF(−) combination can maintain more than 90% of the initial current density after 65,000 s at 1.58 V. The main reason is the composite interface of MoO₃ NSs and ZIF67 phases with Co–O bonds, C–O–Mo bonds and oxygen vacancies defects facilitates the increase of the active sites and efficient electron transfer rate.