Effective charge separation and rapid transport of photogenerated charge carriers without self-oxidation in transition metal dichalcogenide photocatalysts are required for highly efficient and stable hydrogen generation. Here, we report that a molecular junction as an electron transfer path toward two-dimensional rhenium disulfide (2D ReS 2 ) nanosheets from zero-dimensional titanium dioxide (0D TiO 2 ) nanoparticles induces high efficiency and stability of solar hydrogen generation by balanced charge transport of photogenerated charge carriers. The molecular junctions are created through the chemical bonds between the functionalized ReS 2 nanosheets (e.g., −COOH groups) and −OH groups of two-phase TiO 2 (i.e., ReS 2 −C 6 H 5 C(O)− O−TiO 2 denoted by ReS 2 −BzO−TiO 2 ). This enhances the chemical energy at the conduction band minimum of ReS 2 in ReS 2 −BzO−TiO 2 , leading to efficiently improved hydrogen reduction. Through the molecular junction (a Z-scheme charge transfer path) in ReS 2 −BzO−TiO 2 , recombination of photogenerated charges and self-oxidation of the photocatalyst are restrained, resulting in a high photocatalytic activity (9.5 mmol h −1 per gram of ReS 2 nanosheets, a 4750-fold enhancement compared to bulk ReS 2 ) toward solar hydrogen generation with high cycling stability of more than 20 h. Our results provide an effective charge transfer path of photocatalytic TMDs by preventing self-oxidation, leading to increases in photocatalytic durability and a transport rate of the photogenerated charge carriers.

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Visible-light-driven photocatalytic CO2 reduction using TiO2 that can absorb light of all wavelengths has been sought for over half a century. Herein, we report a phase-selective disordered anatase/ordered rutile interface system for visible-light-driven, metal-free CO2 reduction using a narrow band structure, whose conduction band position matches well with the reduction potential of CO2 to CH4 and CO. A mixed disordered anatase/ordered rutile (Ad/Ro) TiO2 was prepared from anatase and rutile phase-mixed P25 TiO2 at room temperature and under an ambient atmosphere in sodium alkyl amine solutions. The Ad/Ro TiO2 showed a narrow band structure due to multi-internal energy band gaps of Ti3+ defect sites in the disordered anatase phase, leading to high visible light absorption and simultaneously providing fast charge separation through the crystalline rutile phase, which was faster than that of pristine P25 TiO2. The band gap of Ad/Ro TiO2 is 2.62 eV with a conduction band of −0.27 eV, which matches well with the reduction potential of −0.24 VNHE of CO2/CH4, leading to effective electron transfer to CO2. As a result, the Ad/Ro TiO2 provided the highest CH4 production (3.983 μmol/(g h)), which is higher than that of even metal (W, Ru, Ag, and Pt)-doped P25, for CO2 reduction under visible light.