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

Abstract

A kind of composite electrocatalysts with the structure of MoO 3 nanosheets coated by ZIF67 nanocrystals and grown on the nickel foam substrate (ZIF67@MoO 3 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@MoO 3 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@MoO 3 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@MoO 3 NSs@NF electrode also shows the small HER overpotential of 135 mV at 10 mA cm −2 . Furthermore, the voltage of ZIF67@MoO 3 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 RuO 2 /NF(+)//Pt–C/NF(−). And the ZIF67@MoO 3 NSs@NF(+)//ZIF67@MoO 3 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 MoO 3 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. • The composite structure of MoO 3 nanosheets grown on NF and coated by ZIF67 are prepared. • The ZIF67@MoO 3 NSs@NF can use the overpotential(ƞ) of 178 mV to drive 10 mA cm −2 . • It can maintain 90% of the initial current density after 65,000 s for overall water-splitting. • Chemical bonds and oxygen vacancy facilitates the increase of the active sites. • Non-highly conductive oxides can also promote the electrocatalytic activity of MOF composite.