Metal-Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

A novel hierarchical structured photoanode based on metal-organic frameworks (MOFs)-derived porous Co3O4-modified TiO2 nanorod array grown on Si (MOFs-derived Co3O4/TiO2/Si) is developed as photoanode for efficiently photoelectrochemical (PEC) water oxidation. The ternary Co3O4/TiO2/Si heterojunction displays enhanced carrier separation performance and electron injection efficiency. In the ternary system, an abnormal type-II heterojunction between TiO2 and Si is introduced, because the conduction band and valence band position of Si are higher than those of TiO2, the photogenerated electrons from TiO2 will rapidly recombine with the photogenerated holes from Si, thus leading to an efficient separation of photogenerated electrons from Si/holes from TiO2 at the TiO2/Si interface, greatly improving the separation efficiency of photogenerated hole within TiO2 and enhances the photogenerated electron injection efficiency in Si. While the MOFs-derived Co3O4 obviously improves the optical-response performance and surface water oxidation kinetics due to the large specific surface area and porous channel structure. Compared with MOFs-derived Co3O4/TiO2/FTO photoanode, the synergistic function in the MOFs-derived Co3O4/TiO2/Si NR photoanode brings greatly enhanced photoconversion efficiency of 0.54% (1.04 V vs reversible hydrogen electrode) and photocurrent density of 2.71 mA cm(-2) in alkaline electrolyte. This work provides promising methods for constructing high-performance PEC water splitting photoanode based on MOFs-derived materials.