| Recently, photoelectrochemical(PEC) water splitting has attracted wide attention of researchers. PEC water splitting offers the capability of harvesting the energy in solar radiation and transferring it directly to chemical bonds for easy storage, transport, and use in the form of hydrogen. Among the various design of a PEC system, the choice of photoelectrodes is one critical factor because their properties, such as optical characteristics and carrier transportation, determine the system’s performance.Among the various transition metal oxides, In2O3 stands out as having suitable characteristics for PEC applications, including appropriately positioned conduction and valence bands for water splitting, good conductivity and high stability.However,research on In2O3 as a photoanode is progressing at a slow pace due to the limitations presented by its wide band-gap(3.5 e V).Therefore, the modification of highly efficient In2O3 nanostructures with good light-harvesting capability is of great importance.1. To achieve highly efficient PEC performance, noble metal nanoparticles such as Ag, Au and Pt etc. have been extensively adopted in photoelectrode materials. Because they can act as photosensitizers to strengthen the optical absorption in visible light and enhance the absorption intensity through the localized surface plasma resonance(LSPR)effect. Meanwhile, the junctions formed between the semiconductor and noble metal nanoparticles can facilitate the separation of photogenerated charge carriers, thereby improving the efficiency of PEC conversion.2. The construction of type-II heterojunction between In2O3 and suitable narrow bandgap semiconductors has been demonstrated as a potential solution to address this issue. These heterostructures usually involve two(wide and narrow) bandgap semiconductors to form the type-II staggered band alignment heterostructure, enabling not only the broad absorption of visible light but also the inhibition of charge recombination process. However, the design of In2O3 composited with narrow bandgap semiconductor is limited because the conduction band potential for In2O3 is too negative.In principle, the band mismatch problem can be solved if the conduction band edge of In2O3 is lowered by formation of shallow donor energy levels in the bandgap of In2O3(2.8 e V). To adopt this strategy, we have fabricated In2O3/In2S3 nanocubes to enhance the PEC properties. Nevertheless, it is still of great challenge to further improve thePEC performance of In2O3/In2S3 nanocubes.3. In this work, for the first time, we report the synthesis of three-component In2O3/In2S3/Ag nanocubes by an effective electrodeposition method, which combines the shallow donor energy levels, heterostructure formation and noble metal modification together in order to further improve the PEC performance. It is demonstrated that the three-component In2O3/In2S3/Ag heterostructure nanocubes show significantly enhanced PEC performance as compared with the pristine In2O3 nanocubes and two-component(In2O3/Ag, In2O3/In2S3) systems.The enhanced PEC properties of In2O3/In2S3/Ag heterojunction is direct consequence of the synergetic effects of enhanced visible light absorption and effective carriers separation on the surface of narrow band-gap semiconductor shell heterostructure via the Ag nanoparticles.4. An important way to modify the PEC photoelectrode is combining two or more than two kinds of semiconductors to form a composite material. Due to the synergistic effect, which makes up for their deficiencies, promotes the separation of photogenerated charge carriers, expands the material spectral response range and improves the light stability. For In2O3 nanocubes of wide band gap and poor response to visible light,furthermore, there is still room for improvement of two-component system In2O3/In2S3 and Cu In S2 owns excellent optical performance advantage so that we suspect that it may be able to further improve the PEC performance of two-component system In2O3/In2S3 composite. We design a kind of In2O3/In2S3/Cu In S2 nano-photelectrode with three component structure. We have used the method of solvent thermal deposition on the surface of In2O3/In2S3 with a layer of Cu In S2 film. The experimental results show that the three-component In2O3/In2S3/Cu In S2 heterojunction has obvious PEC properties compared with In2O3 and In2O3/In2S3 nanocubes. |
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