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 Co 3 O 4 ‐modified TiO 2 nanorod array grown on Si (MOFs‐derived Co 3 O 4 /TiO 2 /Si) is developed as photoanode for efficiently photoelectrochemical (PEC) water oxidation. The ternary Co 3 O 4 /TiO 2 /Si heterojunction displays enhanced carrier separation performance and electron injection efficiency. In the ternary system, an abnormal type‐II heterojunction between TiO 2 and Si is introduced, because the conduction band and valence band position of Si are higher than those of TiO 2 , the photogenerated electrons from TiO 2 will rapidly recombine with the photogenerated holes from Si, thus leading to an efficient separation of photogenerated electrons from Si/holes from TiO 2 at the TiO 2 /Si interface, greatly improving the separation efficiency of photogenerated hole within TiO 2 and enhances the photogenerated electron injection efficiency in Si. While the MOFs‐derived Co 3 O 4 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 Co 3 O 4 /TiO 2 /FTO photoanode, the synergistic function in the MOFs‐derived Co 3 O 4 /TiO 2 /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.