Ligand-Assisted Coordinative Self-Assembly Method to Synthesize Mesoporous Zn_xCd_1–xS Nanospheres with Nano-Twin-Induced Phase Junction for Enhanced Photocatalytic H₂ Evolution

Abstract

The designed synthesis of nanotwin architectures and thus-induced phase junctions expresses huge significance for semiconductor photocatalysts. However, current methods of producing nanotwins mainly involve high-temperature thermal treatment and tedious reaction steps, generally resulting in large bulk structure with ill-defined morphology and low specific surface area. Here, we propose a mild ligand-assisted coordinative self-assembly method to synthesize uniform mesoporous Zn x Cd 1−x S nanospheres with ultrahigh surface areas (148−312 m 2 g −1 ) and controllable diameter (90−370 nm). Moreover, the sample possesses abundant phase junctions induced by nanotwins containing both hexagonal and cubic segments. With the synergy of the twininduced phase junctions and high surface area, the as-prepared mesoporous Zn 0.82 Cd 0.18 S nanospheres exhibit a remarkable photocatalytic H 2 evolution rate of 13.46 mmol h −1 g −1 with free noble metal. The mechanism of photocarrier dynamics was studied by transient photovoltage spectroscopy, manifesting that the photocarrier lifetime of Zn 0.82 Cd 0.18 S is largely prolonged and therefore improves the charge separation efficiency and photocatalytic activity.

Cd0.5Zn0.5S/CoWO4 Nanohybrids with a Twinning Homojunction and an Interfacial S-Scheme Heterojunction for Efficient Visible-Light-Induced Photocatalytic CO2 Reduction

“…In recent years, chalcogenides have been extensively used in photocatalytic CO 2 reduction by virtue of their narrow band gap and negative conduction band in the energy levels. − Among the chalcogenides, ZnS, CdS, MoS 2 , and Cd x Zn 1– x S have been often reported. Moreover, a Cd x Zn 1– x S solid solution has been widely used in the hydrogen evolution and photodegradation of effluents due to its tunable band structure and edge position of the absorption band. − Meanwhile, research on the photocatalytic CO 2 reduction has been receiving attention from people. , Many results demonstrated that the prepared Cd x Zn 1– x S exhibited the best photocatalytic performance while the molar ratio of Cd/Zn was 1 . However, the charge transfer ability of Cd 0.5 Zn 0.5 S (CZS) was greatly limited in consequence of the reintegration of photogenerated electron/hole pairs over CZS and its small specific surface area, so as to result in its low photocatalytic activity for CO 2 reduction.…”

Cation exchange synthesis of porous Cd1‐xZnxS twinned nanosheets for visible light highly active H2 evolution

“…51 The porous twinned structures have two functions: to enhance the light-absorption efficiency and the charge carriers' transfer rate and to afford sufficient transport routes to reagent and product molecules, which could dramatically improve the photocatalytic hydrogen evolution efficiency. 52,53 In order to verify the durability and recovery performance of porous Cd 0.5 Zn 0.5 S twinned nanosheets, the photocatalytic activity of Cd 0.5 Zn 0.5 S was studied under 16 h of visible light irradiation (Figure 9B). Obviously, it can be seen that after four cycles, the photocatalytic activity of porous Cd 0.5 Zn 0.5 S twinned phase junction nanosheets do not decrease significantly, indicating that porous Cd 0.5 Zn 0.5 S twinned nanosheets have good optical stability which is further confirmed by the XRD patterns and XPS spectra of porous Cd 0.5 Zn 0.5 S twinned nanosheets Cd 0.5 Zn 0.5 S before and after photocatalytic reactions (Figure S3).…”

“…Photogenerated holes converge in the valence band of the WZ phase to the twin plane and photooxidation occurs on the surface. 25,53 The enhancement of photocatalytic activity can be attributed to the designed Cd 0.5 Zn 0.5 S structure possessing both porous structure and nano twin structure, which can form an effective photocatalytic system. (i) The porous structure can remarkably abridge the path of electron transfer and broaden the light utilization by prolonging the time of light reaction in the pore walls.…”

“…Porous Cd 0.5 Zn 0.5 S twinned phase junction nanosheets have better photocatalytic hydrogen production performance due to their excellent energy band structure, remarkable charge mobility, and abundant active centers 51 . The porous twinned structures have two functions: to enhance the light‐absorption efficiency and the charge carriers' transfer rate and to afford sufficient transport routes to reagent and product molecules, which could dramatically improve the photocatalytic hydrogen evolution efficiency 52,53 . In order to verify the durability and recovery performance of porous Cd 0.5 Zn 0.5 S twinned nanosheets, the photocatalytic activity of Cd 0.5 Zn 0.5 S was studied under 16 h of visible light irradiation (Figure 9B).…”

“…Under illumination, excited electrons and holes are separated at the junction of two phases, and photogenerated electrons are directed to gather in the conduction band of the ZB phase (away from the twin plane) and transferred to the surface for photoreduction reaction. Photogenerated holes converge in the valence band of the WZ phase to the twin plane and photooxidation occurs on the surface 25,53 . The enhancement of photocatalytic activity can be attributed to the designed Cd 0.5 Zn 0.5 S structure possessing both porous structure and nano twin structure, which can form an effective photocatalytic system.…”