Photochemical hydrogen production under visible light irradiation represents one of the most challenging issues in solar energy conversion. Intensive efforts have been made to achieve this goal for the last 30 years. Among them, dye-sensitized semiconductor oxides (e.g., TiO₂) have been frequently studied and shown promising results. In such systems, an efficient visible light sensitization requires a strong binding between TiO₂ surface and sensitizers. Many sensitizers such as Ru-complexes, metaloporphyrins and Pt-complexes can be attached to TiO₂ surface through chemical anchoring groups (e.g., carboxylate linkage). In this study, we used water-soluble tin-porphyrin [SnIV (OH2)2TPyHP]6+(SnP) to achieve a non-attached SnP/TiO₂ system for photocatalytic hydrogen production. Although SnP hardly adsorbs on TiO₂, hydrogen was successfully produced under visible light. The electron transfer from the sensitizer to TiO₂ conduction band is believed to occur through a collisional mechanism. The high charge on Sn(IV) makes the SnP ring the most electrophilic one among all metaloporphyrins. Therefore, the excited state of SnP (SnP*) has a high electron affinity, favoring the formation of reduced SnP (SnP-) which is relatively stable and long-lived. The subsequent electron transfer from SnP- to TiO₂ results in the production of hydrogen. This porphyrin-sensitized production of hydrogen was compared with the conventional anchored sensitized systems employing ruthenium bipyridyl complexes. Ru-complexes with hexacarboxylate (C6) and diphosphonate (P2) as the anchoring group were selected. The amount of H₂ produced in SnP/TiO₂ was significantly higher than that in C6/TiO₂ and similar to P2/TiO₂.