Photochemical Ammonia Synthesis over Reduced Polyoxovanadate-Intercalated Defective ZnAl Layered Double Hydroxide Nanosheets

Abstract

The exploration of efficient and stable N 2 fixation photocatalysts featuring a broad absorption spectrum and N 2 fixation active sites has become specifically conspicuous. Herein, a series of reduced polyoxovanadates (POVs) were intercalated into copper-induced ZnAl layered double hydroxide (0.5%-ZnAl LDH) nanosheets with oxygen vacancies via an anion exchange strategy toward green ammonia production. The intervalence charge transfer arising from mixedvalence POV materials is responsible for its light-harvesting behavior, and the LDHs lay the foundation for the chemical adsorption and activation process of nitrogen molecules; both contributions facilitate the nitrogen photofixation performance of such composite materials. As predicted, the catalytic efficiency of V 34 /0.5%-ZnAl is 7.0 times higher than 0.5%-ZnAl LDH. Therefore, such an all-inorganic system exhibits an apparent quantum efficiency of 0.3137% at 500 nm. The strategy of "working in tandem" established by POV-based light-absorber species and oxygen vacancies as the sites for N 2 activation is extremely vital for enhanced ammonia formation. This work opens up a versatile insight for the rational design of an efficient photo-driven nitrogenreduction composite catalyst toward sustainable ammonia production compared to the industrial Haber−Bosch process.

Photosynthetic System Based on a Polyoxometalate-Based Dehydrated Metal–Organic Framework for Nitrogen Fixation

“…Figure d shows the C 1s spectra, which can be deconvoluted into three fitted peaks centered at 288.6, 285.9, and 284.5 eV and are assigned to the C–O, CC, and C–C bonds, respectively . The V 2p 3/2 and V 2p 1/2 peaks of SiW 9 V 3 @d-UiO-66 can be observed at energies of 518.3 and 524.6 eV, respectively (Figure e) Figures S9–S11 show the Zr 3d, W 4f, C 1s, and O 1s spectra of the as-prepared composites, respectively.…”

“…The X-ray diffraction (XRD) patterns of POMs@d-UiO-66 composites are identical to those of d-UiO-66, illustrating that POMs encapsulated into the d-UiO-66 cages as separated clusters barely influence the construction of the classical frameworks (Figures d and S2). The UV–vis diffuse reflectance spectroscopy (UV-DRS) absorption spectra of SiW 9 V 3 and SiW 9 Fe 3 display a better absorption than SiW 12 from 400 to 800 nm, which may be attributed to the charge transfer between metals . SiW 9 Fe 3 @d-UiO-66 displays a broad absorption range and an obvious red shift compared to d-UiO-66, which can be profitable to improve the utilization of light and provide a remarkable advantage for PNR reactions (Figures f and S3).…”

New two fold interpenetrating 3D polyoxovanadate-based metal–organic framework as bifunctional catalyst for the removal of 2-chloroethyl ethyl sulfide and phenolic compounds

“…[33]. Reasonable assembly of metalorganic cationic structural units and POVs can not only enrich the structure of this type of solid-phase material but also facilitate the synergistic effect of metal ions, organic ligands, and POVs to optimize the properties [34][35][36][37][38]. Chen et al synthesized a discrete tetranuclear vanadium metal-organic complex…”

Photocatalytic Nitrogen Fixation Coupled with the Generation of Value-Added Chemicals from N2 and Cellulose over MoO3 Nanosheets

“…It is obvious that the Haber–Bosch method not only requires a high cost of hydrogen and fossil fuels but also emits 1.4% global carbon dioxide (CO 2 ) emission . In recent years, photocatalytic and electrocatalytic nitrogen fixation pathways that evolve NH 3 from N 2 at constant pressure and room temperature were identified as simple and sustainable NH 3 preparation methods. − It should be noted that photocatalytic nitrogen fixation driven by solar energy is a more attractive NH 3 preparation strategy due to its sustainability and low cost, but the construction of an ideal photocatalytic nitrogen fixation reaction with the equation of 2N 2 + 6H 2 O = 4NH 3 + 3O 2 is very difficult in thermodynamics because of the absence of an efficient active site for water oxidation reaction. To enhance the NH 3 generation activity, the photocatalytic nitrogen fixation reaction was realized in a half-reaction system by using an electron donor as the sacrificial reagent .…”