Composition-Tuned ZnO/Zn_xCd_1–xTe Core/Shell Nanowires Array with Broad Spectral Absorption from UV to NIR for Hydrogen Generation

Abstract

For highly efficient photoelectrodes, the materials used must have both a broad absorption range and large separation efficiency of photogenerated electron-hole pairs. Type II heterostructures with a ternary shell meet these two requirements and thus are recognized as being an ideal materials system for application in photocatalytic hydrogen production. Here, a ZnO/ZnxCd1-xTe core/shell nanowires array with a broad absorption edge from UV (380 nm) to NIR (855 nm) was fabricated via a chemical vapor-deposition method. More importantly, the ZnO/ZnxCd1-xTe core/shell nanowires array are highly single crystalline, and the composition can be continuously tuned by optimizing the deposition temperature, making the design of the desired photocatalyst possible. As expected, the single-crystalline ternary ZnxCd1-xTe shell greatly enhances the charge separation efficiency and prolongs the lifetime of photogenerated charge carriers, which contribute to the high photocatalytic and photoelectrocatalytic activity under light irradiation. In addition, ZnO/ZnxCd1-xTe core/shell structure show remarkable photocatalytic H2-production activity and high H2-production capability because of the synergistic light absorption of the ternary ZnxCd1-xTe shell and the formation of a type II heterostructure at the interface between the ZnO core and ZnxCd1-xTe shell. This work provides a new material platform for the design of highly efficient solar-fuel devices that demonstrate a broad and controllable absorption from the UV to NIR wavelengths.

Enhanced photoelectrochemical and photocatalytic activities of CdS nanowires by surface modification with MoS2 nanosheets

“…Compared with the well-crystallinity of CdS NWs, the MoS 2 layer is polycrystalline although there are some crystalline domains with random lattice fringes. A closer examination of the interface between MoS 2 and CdS shows that the inconspicuous lattice fringes of MoS 2 directly connect to the continuous lattice fringes of CdS, which is expected to facilitate the separation and transfer of photogenerated charge carriers [27,31]. Further increasing molar ratio of MoS 2 loading to 20%, as shown in Fig.…”

Review of one-dimensional and two-dimensional nanostructured materials for hydrogen generation

“…59 n-n type heterojunctions yield similar results. 35 In the case of photo- 17 due to shorter collection times. Light reflection increases the ratio of non-diffusive absorption and diffusive scattering, which results in a reduction in photon harvesting.…”

“…For example, Zn x Cd 1Àx Te in conjunction with ZnO in heterostructures helps to extend the absorption of solar energy into the NIR region, which can be as high as 22% of the solar spectrum. 35 In the process of fabrication, inorganic nanostructures are generally subjected to thermal treatment(s), note that there are exceptions. Various studies have shown the dependence of H 2 production on processing parameters, such as the calcination temperature.…”

Vertically aligned TiO2/(CdS, CdTe, CdSTe) core/shell nanowire array for photoelectrochemical hydrogen generation

“…IIeVI group semiconductors (e.g., CdS, CdSe, ZnSe) have been widely chosen as sensitizer layer because of their appropriate optical properties, abundance, easy manufacture [26e29]. Compared with the most studied binary IIeVI semiconductors, ternary alloy semiconductor materials (e.g., ZnCdSe [25,30,31], ZnCdTe [32], CdSSe [33,34]) distinguish themselves by many advantages, such as the tunable band gaps [35,36], synergistic effects for the light harvesting [26,37] and higher chemical stability [38,39]. In 2013, Pan et al [39] studied the CdSe x Te 1Àx alloyed quantum dots (QD) sensitized solar cell (QDSSC) based on mesoporous TiO 2 film, and found that the CdSe x Te 1Àx QDs enormously broadened the light absorption of the QDSSC into near infrared range and the solar energy conversion efficiency reached above 6%.…”

“…In 2013, Pan et al [39] studied the CdSe x Te 1Àx alloyed quantum dots (QD) sensitized solar cell (QDSSC) based on mesoporous TiO 2 film, and found that the CdSe x Te 1Àx QDs enormously broadened the light absorption of the QDSSC into near infrared range and the solar energy conversion efficiency reached above 6%. Recently, Zhan et al [32] synthesized a composition-tunable ternary alloy ZnO/ Zn x Cd 1Àx Te core/shell nanowire arrays which exhibited significantly enhanced PEC hydrogen generation activity. In the previous report of our group, we reported a TiO 2 /CdS x Se 1Àx (0 < x < 1) core/ shell NWAs photoelectrode and demonstrated that the alloying of CdS and CdSe on TiO 2 NWAs greatly improved the PEC hydrogen generation performance, especially in case of TiO 2 /CdS 0.52 Se 0.48 composite electrode, due to the enhanced light absorption and charge separation [40].…”