Approach of fermi level and electron-trap level in cadmium sulfide nanorods via molybdenum doping with enhanced carrier separation for boosted photocatalytic hydrogen production.

Doping semiconductor with non-noble metal is a promising strategy to modulate the electronic structures and therefore develop efficient photocatalysts. In this study, we report a facile one-pot solvothermal strategy to synthesize Mo-doped CdS nanorods (NRs) using ammonium tetrathiomolybdate as the sources for both of S and Mo, cadmium acetate as the Cd source, and ethanediamine as the solvent heated at 180 °C for 24 h. The experimental characterizations and theoretical calculations reveal that Mo in the form of Mo4+ is incorporated into the CdS lattice to substitute Cd2+ ions and the Mo-S-Cd bonds are formed accordingly. The Mo doping not only introduces localized electron-trapping states at the bottom of conduction band minimum, but also elevates the Fermi level towards the defect level, which endows the doped system with enhanced n-type characteristic and the defect state with strong electron-trapping ability. Moreover, a nonuniform distribution of charge density is formed for the Mo-doped CdS NRs, facilitating the separation of photoexcited charge carriers. Therefore, the Mo-doped CdS NRs exhibit remarkably enhanced photocatalytic activity, with an average H2 production rate of 14.62 mmol·g-1·h-1 without using Pt as the co-catalyst, about 5.8 times higher than that of bare CdS. This work provides new insight into the facile synthesis of visible-light-driven photocatalysts as well as the effect of metal ion doping on the modulation of electronic structures.