MOF derived NiO thin film formed p-n heterojunction with BiVO4 photoelectrode for enhancement of PEC performance

Metal-organic frameworks (MOFs) derived metal oxides with large surface and more metal active sites were beneficial for photoelectrochemical (PEC) water splitting. In this work, we used a novel and easy method for the Ni-MOF attached on BiVO4 photoelectrode surface by electrostatic attraction, afterwards the Ni-MOF/BiVO4 photoelectrodes were annealed at muffle to obtain MOF derived NiO/BiVO4 p-n heterojunction composite photoelectrodes. The thickness of NiO thin film with ultrathin structure was tested by atomic force microscopy (AFM). The photoelectrochemical (PEC) performance of NiO/BiVO4 composites photoelectrodes for water splitting was enhanced compared to the pure BiVO4 photoelectrode. The best NiO/BiVO4 photoelectrodes with about 70 nm thickness of NiO thin film showed the max photocurrent density with 1.94 mA/cm2 (1.23 V vs RHE) which was about 4.2 times than the pure BiVO4 with 0.46 mA/cm2 (1.23 V vs RHE). The charge injection and separation efficiency of NiO/BiVO4 photoelectrodes enhancement indicate that the NiO as a co-catalysis and form p-n heterojunction has improved the photoexcited carrier mobility which was benefited for the PEC per-formance of water splitting.

Automated summary

In this work, a novel and easy method was used to attach Ni-MOF on the surface of BiVO4 photoelectrode via electrostatic attraction. The resulting Ni-MOF/BiVO4 photoelectrodes were then annealed to obtain MOF derived NiO/BiVO4 p-n heterojunction composite photoelectrodes. The NiO/BiVO4 composite photoelectrodes showed enhanced photoelectrochemical performance for water splitting compared to pure BiVO4 photoelectrode.