We report the fabrication of 2D ZnIn2S4 nanosheet/1D TiO2 nanorod heterojunction arrays by a facile hydrothermal process and their use as photoelectrodes in a photoelectrochemical (PEC) cell for high-performance solar water splitting. The morphology, microstructure, and phase of pristine TiO2 and 2D ZnIn2S4 nanosheet/1D TiO2 nanorod heterojunction arrays were characterized in detail. PEC measurements showed that 2D/1D heterojunction arrays offered enhanced photocurrent density (3 times higher than that of pristine TiO2), negatively shifted onset potential from 0.05 to -0.53 V, and high light on/off cycle stability. Electrochemical impedance investigation attested to a significant improvement of the interface electron transfer kinetics in this heterojunction, thus facilitating electron-hole separation, transfer, and collection, which resulted in enhanced PEC properties.
In a photoelectrochemical (PEC) cell for water splitting, the critical issue is charge separation and transport, which is usually completed by designing semiconductor heterojunctions. TiO2 anatase-rutile mixed junctions could largely improve photocatalytic properties, but impairs PEC water splitting performance. We designed and prepared two types of TiO2 heterostructures with the anatase thin film and rutile nanowire phases organized in different sequences. The two types of heterostructures were used as PEC photoanodes for water splitting and demonstrated completely opposite results. Rutile nanowires on anatase film demonstrated enhanced photocurrent density and onset potential, whereas strong negative performance was obtained from anatase film on rutile nanowire structures. The mechanism was investigated by photoresponse, light absorption and reflectance, and electrochemical impedance spectra. This work revealed the significant role of phase sequence in performance gain of anatase-rutile TiO2 heterostructured PEC photoanodes.
The traditional photodetectors based on photoelectric effect exhibit inferior response or even out of operation with the decrease of temperature. However, cryogenic visible light detection is increasingly demanded in deep space and polar exploration. Herein, a self‐powered visible photodetector coupling pyroelectricity and photoelectricity to optimize the cryogenic detecting performance is designed in which hydrothermally grown CdS nanorod array is covered by SnS nanoflakes. The choice of SnS allows the detector with strong visible light absorption and great photoelectric conversion efficiency, while the CdS nanorod structure with pyroelectricity can effectively modulate the behavior of photogenerated carriers at low temperatures. It is found that the response characteristics of the photodetector are dominated by the combination of pyroelectric and photoelectric effects, which becomes more significant with the reduced temperature. Specifically, at 130 K temperature, the photoresponse current under 650 nm light is improved by 7.5 times as that at room temperature, while the ratio of pyroelectric current to photocurrent can be increased to 400%. Meanwhile, the responsivity and detectivity are as high as 10.4 mA W−1 and 3.56 × 1011 Jones, respectively. This work provides a promising approach to develop high‐performance self‐powered visible photodetectors with low‐temperature operating capability.
CdS is a promising visible light response photoanode of photoelectrochemical (PEC) water splitting, but it remains a great challenge for practical application, due to the photohole‐induced self‐corrosion, and sulfide/sulfite ions as hole scavengers are always necessary for stable solar hydrogen generation. Herein, a CdS/SnSx nanorods/nanosheets hierarchical heterostructure with novel phase‐engineered band alignment is rationally designed via a two‐step solution reaction route for PEC water splitting. In the Na2SO4 aqueous electrolyte without any hole scavengers, compared with the pristine CdS, the CdS/SnSx photoanode achieves a remarkably enhanced photocurrent density of 1.59 mA cm−2 and a considerable stability at bias potential 1.23 V versus reversible hydrogen electrode (RHE) under simulated sunlight. It is proposed that the deposited SnSx nanosheets not only act as protective layers to restrain the photocorrosion of CdS, but also facilitate the charge separation in CdS by the virtue of the Type II heterojunction formed between CdS and SnSx.
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