Effect of Co-Based Metal-Organic Framework Prepared by an In Situ Growth Method on the Photoelectrochemical Performance of Electrodeposited Hematite Photoanode

The Co-based metal-organic framework (Co-MOF) is successfully prepared on the Ti-modified hematite nanosheet photoelectrode via a simple in situ hydrothermal method, and the sample is named as Co-MOF@TiFe. Under the bias potential of 1.23 and 1.43V (vs reversible hydrogen electrode [RHE]), the photocurrents of the Co-MOF@TiFe photoanode are 1.24 and 1.78mAcm(-2), respectively. Furthermore, the onset potential of the Co-MOF@TiFe photoanode is negatively shifted by about 120mV than that of the Ti-modified hematite sample. At 1.23V (vs RHE), the enhanced photoelectrochemical (PEC) performance of the Co-MOF@TiFe photoanode is attributed to its substantially increased surface charge injection efficiency and its small increased bulk charge separation efficiency. The reasons for the increased surface charge injection efficiency are its decreased surface states 1 (SS1), the appearance of surface states 2 (SS2), and the Co-MOF acting as a catalyst. The increased bulk charge separation efficiency is attributed to the formation of the hematite/Co-MOF heterojunction and the rougher surface caused by etching. Herein, the effects of the in situ prepared Co-MOF coating on the crystalline structure, morphology, and PEC performance of Ti-modified hematite are systematically investigated by characterization.