Construction of {M4O4} motifs is an effective design paradigm for molecular, polyoxometalate- and oxide-based water oxidation catalysts (WOCs). However, the mechanisms beneath this bio-inspired design strategy remain under intense debate. The two modifications of LiCoO2 with spinel-type and layer structures are an exceptionally versatile model system to explore the correlations between structure, electronic properties and photochemical water oxidation. The electronic properties of both LiCoO2 modifications are tuneable through delithiation while maintaining the basic structural frameworks. This provides a unique opportunity to assign the respective influence of structures and electronic properties on the water oxidation properties. While spinel-type LiCoO2 with {Co4O4} cubane motifs is active for photochemical water oxidation, the layered modification without cuboidal structural elements is nearly inactive. Here, we demonstrate that the water oxidation performance of both modifications can be significantly improved through chemical delithiation. A wide range of analytical methods were applied to investigate the transition of electronic properties upon delithiation, and a direct correlation between enhanced hole mobility and improved water oxidation activity was established. The difference in water oxidation activity between the two structural modifications was further linked to the role of {Co4O4} cubane motifs in constructing 3D Co-O-Co networks with expanded hole transfer paths. Thus, the promoting effects of both delithiation and {Co4O4} cubane motifs on water oxidation can be consistently explained by enhanced hole mobility.