Photocatalytic mineralization of recalcitrant contaminants like phenol in wastewater requires abundant hydroxyl radicals (·OH) to initiate the reaction prior to the ring-opening. We here increase the free energy for adsorption of O^* species on TiO₂ surface and slightly downshift the band position by tin doping. This can simultaneously promote the generation and suppress the annihilation of ·OH. Besides, tin doping can also facilitate semiconductor-cocatalyst-solution (SCS) interfacial electron transfer by lowering the potential barrier and synergistically enhance the photon utilization. By filming the photocatalyst onto our developed fixed bed reactors, the loss of photons resulting from undesirable absorption by contaminants can be alleviated. By these virtues, trace amount of phenol in wastewater can be efficiently mineralized.