ZnSe and CdS Co-Sensitized TiO₂ Nanorod Arrays as Photoanodes for Bias-Free Solar Hydrogen Evolution

The efficient charge separation and surface state reactions are significant in enhancing the efficiency of photoelectrochemical hydrogen evolution. Herein, we report a ternary heterostructure consisting of CdS/ZnSe sensitized TiO₂ nanorod as a photoanode. The heterojunction photoanode considerably widens the photon absorption spectral range and thereby enhances the photocurrent density up to 2 mA/cm² at 1.23 V versus RHE which is 10 times higher than pristine TiO₂ photoanode. The photoelectrochemical results demonstrate a high photocurrent density of 2 mA/cm² with a photon-to-current conversion efficiency of 1.5 % at a very low applied bias (0.2 V vs RHE). The improved PEC performances of the multidimensional hybrid photoanode could be ascribed to the efficient visible-light absorption of ZnSe and CdS nanocrystals decorated on the surface of 1D TiO₂ . The rapid electron-transfer properties owing to higher carrier density, low carrier transport resistance, and an extended lifetime of photoexcited carriers in the multidimensional ZnSe/CdS/TiO₂ heterostructure with suppressed surface charge recombination are responsible for enhanced hydrogen evolution activities.