Dinitrogen photofixation properties of different titanium oxides in conducting polymer/titanium oxide hybrid systems

Titanium oxide layers prepared by hard (rutile and anatase types) and soft processes (anodic amorphous oxides prepared in an aqueous phosphoric, TiOxw, and a dichloromethane/electrolyte solution, TiOxo) were brought into contact with the ClO4−-doped poly(3-methylthiophene) (P3MeT) film, and their ability to photofix atmospheric dinitrogen was compared. The comparisons revealed that the latter junctions using amorphous oxides produced larger amount of N2-fixation products than the former two junctions and that the P3MeT/TiOxw junction exhibited a higher N2-fixation rate than the P3MeT/TiOxo cell. The TiOxw and TiOxo layers were characterized by transmission electron microscopic observations, X-ray electron dispersive analysis, and selected area electron diffraction measurements, and the higher activity of the TiOxw layer was rationalized on the basis of the contact potential difference measurements. Additionally, the dependences of the N2-fixation yield on the photoirradiation time, P3MeT film thickness, and anodizing potential during the formation of the TiOxw were investigated using the most active P3MeT/TiOxw junction cell.