Zinc vacancy (VZn) is successfully introduced into 3D hierarchical ZnIn2S4 (3D‐ZIS). The photo‐electrochemical experiments demonstrate that the charge separation and carrier transfer are more efficient in the 3D‐ZIS with rich VZn. Of note, for the first time, it is found that VZn can decrease the carrier transport activation energy (CTAE), from 1.14 eV for Bulk‐ZIS (Bulk ZnIn2S4) to 0.93 eV for 3D‐ZIS, which may provide a feasible platform for further understanding the mechanism of photocatalytic CO2 reduction. In situ Fourier transform infrared (FT‐IR) results reveal that the presence of rich VZn ensures CO2 chemical activation, promoting single‐electron reduction of CO2 to CO2−. In addition, in situ FT‐IR and CO2 temperature programmed desorption results show that VZn can promote the formation of surface hydroxyl. To the best of current knowledge, there are no reports on the photoreduction of CO2 simply by virtue of 3D‐ZIS with VZn and few literature reports on the photocatalytic reduction of CO2 concerned with CTAE. Additionally, this work finds that surface hydroxyl may play a crucial role in the process of CO2 photoreduction. The work may provide some novel ways to ameliorate solar energy conversion performance and a better understanding of photoreaction mechanisms.
The influence of defects on quantitative
carrier dynamics is still
unclear. Therefore, full-spectrum responsive metallic ZnIn2S4 (VIn-rich-ZIS) rich in indium vacancies
and exhibiting high CO2 photoreduction efficiency was synthesized
for the first time. The influence of the defects on the carrier dynamic
parameters was studied quantitatively; the results showed that the
minority carrier diffusion length (L
D)
is closely related to the catalytic performance. In situ infrared
spectroscopy and theoretical calculations revealed that the presence
of indium vacancies lowers the energy barrier for CO2 to
CO conversion via the COOH* intermediate. Hence, the high rate of
CO evolution reaches 298.0 μmol g–1 h–1, a nearly 28-fold enhancement over that with ZnIn2S4 (VIn-poor-ZIS), which is not rich
in indium vacancies. This work fills the gaps between the catalytic
performance of defective photocatalysts and their carrier dynamics
and may offer valuable insight for understanding the mechanism of
photocatalysis and designing more efficient defective photocatalysts.
It is of great importance to understand the relationship between the structure and properties at the atomic level, which provides a solid platform for the design of efficient heterogeneous catalysts. However, it remains a challenge to elucidate the roles of the structure of reaction sites in the catalytic activity of active sites due to the lack of understanding of the structure of specific active site species. Herein, taking the metal− organic framework (MOF) UiO-66(Zr) as a prototype, MOF catalysts with all-solid-state frustrated Lewis pairs (FLPs) Zr 3+ −OH were synthesized in situ by adding acetic acid (HAc) as a modulator. By introducing missing linkers, UiO-66(Zr) first becomes a visible-light-responsive photocatalyst for CO 2 reduction. The in situ Fourier transform infrared (FTIR) spectrum reveals that b-CO 3 2− is the key intermediate for the activation of CO 2 molecules through FLPs Zr 3+ −OH. Moreover, defective UiO-66(Zr) could "self-breath" by surface hydroxyls. This finding not only provides a new avenue for utilizing UV-responsive MOFs by defect engineering but also sheds light on its catalytic activity at the atomic level.
A novel cage-based crystalline covalent organic framework, i.e. Cage-COF-TT (TT = triammonia–terephthalaldehyde), was prepared from a prism-like triammonia-containing molecular cage and terephthalaldehyde.
Design and development of highly efficient photocatalytic materials are key to employ photocatalytic technology as a sound solution to energy and environment related challenges. This work aims to significantly boost photocatalytic activity through rich indium vacancies (VIn) In2S3 with atomic p–n homojunction through a one‐pot preparation strategy. Positron annihilation spectroscopy and electron paramagnetic resonance reveal existence of VIn in the prepared photocatalysts. Mott–Schottky plots and surface photovoltage spectra prove rich VIn In2S3 can form atomic p–n homojunction. It is validated that p–n homojunction can effectively separate carriers combined with photoelectrochemical tests. VIn decreases carrier transport activation energy (CTAE) from 0.64 eV of VIn‐poor In2S3 to 0.44 eV of VIn‐rich In2S3. The special structure endows defective In2S3 with multifunctional photocatalysis properties, i.e., hydrogen production (872.7 µmol g−1 h−1), degradation of methyl orange (20 min, 97%), and reduction in heavy metal ions Cr(VI) (30 min, 98%) under simulated sunlight, which outperforms a variety of existing In2S3 composite catalysts. Therefore, such a compositional strategy and mechanistic study are expected to offer new insights for designing highly efficient photocatalysts through defect engineering.
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