Abstract
The growing demands for reproducible and clean sources of power has prompted the exploitation of novel materials for solar-energy conversion; in any case, the improvement of their conversion efficiency remains a big challenge. We report a mixed-dimensional heterostructure to synchronously enhance charge separation and light-absorption of the photoanodes via the introduction of two-dimensional reduced graphene oxide and zero-dimensional CuSbS2 quantum dots on one-dimensional TiO2 arrays. The experimental results show that the graphene sheets with a low Fermi level and a superior electron mobility accept photo-excited electrons from TiO2 and enable fast electron transportation; while the CuSbS2 quantum dots promote the visible light-absorption of the photoanode. The synergistic effects in this mixed-dimensional (1D–2D–0D) heterostructure photoanode induce a markedly raised photoconversion efficiency of 1.2% at 0.3 V and a photocurrent density of 5.5 mA cm−2 at 0.4 V. Furthermore, the photocurrent density of the mixed-dimensional heterostructure exceeds previously reported TiO2-based photoanodes in neutral media. The improved photoelectrochemical properties are attributed to the synergistic-effect-induced highly organized, mixed-dimensional architectures. It is expected that the mixed-dimensional heterostructure photoanode will be a potential candidate for applications in environmental remediation and energy fields.
Highlights
Solar energy is regarded as a feasible alternative to fossil fuels because of its promise for addressing environmental remediation and energy conversion
The CuSbS2 quantum dots are uniformly distributed on the 1D TiO2 nanowires/2D graphene heterostructures, as shown in Fig. 2(c)
A further uorescence decrease was observed for the 0D quantum dots/1D TiO2 nanowires/2D graphene heterostructures photoanode, this might be attributed to the following: (1) the narrow band gap of the CuSbS2 quantum dots promoted the intense absorption of visible light; the potentials of the conduction band (CB) of CuSbS2 were more positive than TiO2, and the photo-generated electrons transferred to TiO2 because of the potential dissimilarity; (2) the higher work function of the graphene sheets promote the transfer of the photo-generated charge carriers at the interface
Summary
Great efforts have been made including the geometry and band structure engineering to solve these problems. One-dimensional (1D) TiO2 including TiO2-tubes, TiO2-rods, TiO2- bers, TiO2-belts, and TiO2-wires recently have attracted wide interest for photoelectrical applications because of their large surface area for light-absorption, as well as an axial transport of photo-generated carriers with fast transport property.[13,14,15,16,17,18] In addition, forming a Schottky or p–n junctions to realize band structure engineering is another effective approach, which aims to widen the visible light-absorption and hinder from the recombination of electrons and holes to improve the photon-to-energy conversion efficiency.[19,20,21] For example, coupling 1D TiO2 with narrow bandgap zerodimensional (0D) quantum dots could enhance the photoconductivity by photogating effect. It is expected that mixed-dimensional heterostructure photoanode will be a promising candidate for applications in environmental remediation and energy elds
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