For the purpose of efficiently utilizing the renewable solar energy, it is of vital importance to understand the key factors that contribute to the performance merits for photocatalysis applications. In this work, we find that anatase titania nanostructures with high efficiency in photoelectrochemical cell (PEC) do not necessarily retain the same good performance when used in direct heterogeneous reaction (DHR). Investigation is carried out to elucidate how the electronic properties of the different nanostructures are correlated with the PEC and DHR efficiencies. Good PEC cell performance is identified to be related to topotactically formed samples with intimately connected particles that facilitate easy charge transfer. Additional benefit for PEC cell is found to be achieved from the vectorial conduction pathway in the pseudo one dimensional structure. On the other hand, high activity of DHR photocatalysis is attributed mainly to the exposed high reactivity crystal facets. The presence of anatase TiO2 {010} facets is identified to enhance electron‐hole separation and create specific surface states that facilitate interactions across the semiconductor/electrolyte interfaces. Different photocatalytic performance–nanostructure correlations are observed on photoelectrochemical cell and direct heterogeneous photocatalysis. It is demonstrated that intimate interparticle connected nanostructures with vectorial charge conduction are favorable in photoelectrochemical cells. For direct heterogeneous photocatalysis, high reactivity facets are more desirable, which have better photoactivated semiconductor/electrolyte interface and better charge separation efficiency.