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1.
Small ; 20(33): e2400348, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38564790

RESUMO

Production of green hydrogen (H2) is a sustainable process able to address the current energy crisis without contributing to long-term greenhouse gas emissions. Many Ag-based catalysts have shown promise for light-driven H2 generation, however, pure Ag-in its bulk or nanostructured forms-suffers from slow electron transfer kinetics and unfavorable Ag─H bond strength. It is demonstrated that the complexation of Ag with various chalcogenides can be used as a tool to optimize these parameters and reach improved photocatalytic performance. In this work, metal-organic-chalcogenolate assemblies (MOCHAs) are introduced as effective catalysts for light-driven hydrogen evolution reaction (HER) and investigate their performance and structural stability by examining a series of AgXPh (X = S, Se, and Te) compounds. Two catalyst-support sensitization strategies are explored: by designing MOCHA/TiO2 composites and by employing a common Ru-based photosensitizer. It is demonstrated that the heterogeneous approach yields stable HER performance but involves a catalyst transformation at the initial stage of the photocatalytic process. In contrast to this, the visible-light-driven MOCHA-dye dyad shows similar HER activity while also ensuring the structural integrity of the MOCHAs. The work shows the potential of MOCHAs in constructing photosystems for catalytic H2 production and provides a direct comparison between known AgXPh compounds.

2.
Adv Mater ; 36(7): e2305730, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-37899494

RESUMO

Thiomolybdates are molecular molybdenum-sulfide clusters formed from Mo centers and sulfur-based ligands. For decades, they have attracted the interest of synthetic chemists due to their unique structures and their relevance in biological systems, e.g., as reactive sites in enzymes. More recently, thiomolybdates are explored from the catalytic point of view and applied as homogeneous and molecular mimics of heterogeneous molybdenum sulfide catalysts. This review summarizes prominent examples of thiomolybdate-based electro- and photocatalysis and provides a comprehensive analysis of their reactivities under homogeneous and heterogenized conditions. Active sites of thiomolybdates relevant for the hydrogen evolution reaction are examined, aiming to shed light on the link between cluster structure and performance. The shift from solution-phase to surface-supported thiomolybdates is discussed with a focus on applications in electrocatalysis and photocatalysis. The outlook highlights current trends and emerging areas of thiomolybdate research, ending with a summary of challenges and key takeaway messages based on the state-of-the-art research.

3.
J Mater Chem A Mater ; 12(31): 19924-19934, 2024 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-39114767

RESUMO

In pursuit of universal access to clean water, photocatalytic water remediation using metal-organic frameworks (MOFs) emerges as a strong alternative to the current wastewater treatment methods. In this study, we explore a unique Ti-based MOF comprised of 2D secondary-building units (SBUs) connected via biphenyl dicarboxylic acid (H2bpdc) ligands - denoted as COK-47 - as a visible-light-driven photocatalyst for organic dye degradation. Synthesized via a recently developed microwave-assisted method, COK-47 exhibits high hydrolytic stability, demonstrates a strong dye uptake, and shows noteworthy dye-degradation performance under UV, visible, and solar light, outperforming benchmark TiO2 and MIL-125-Ti photocatalysts. Due to its nanocrystalline structure and surface termination with organic linkers, COK-47 exhibits selective degradation of cationic pollutants while remaining inert towards anionic dyes, thus highlighting its potential for selective oxidation reactions. Mechanistic studies reveal the involvement of superoxide radicals in the degradation process and emphasize the need to minimize the recombination of photogenerated electron-hole pairs to achieve optimal performance. Post-catalytic studies further confirm the high stability and reusability of COK-47, making it a promising photocatalyst for water purification, organic transformation, and water splitting reactions under visible light.

4.
Sustain Energy Fuels ; 8(6): 1225-1235, 2024 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-38481764

RESUMO

This study investigates the hydrogen evolution reaction (HER) efficiency of two photosystems incorporating an all-inorganic molecular thiomolybdate [Mo3S13]2- cluster as a HER catalyst. First, we delve into the performance of a homogeneous [Mo3S13]2-/[Ru(bpy)3]2+ (Mo3/Ru) dyad which demonstrates high turnover frequencies (TOFs) and apparent quantum yields (AQYs) at 445 nm approaching the level of 0.5%, yet its performance is marked by pronounced deactivation. In contrast, a heterogeneous approach involves anchoring [Mo3S13]2- onto graphitic carbon nitride (GCN) nanosheets through weak electrostatic association with its triazine/heptazine scaffold. [Mo3S13]2-/GCN (Mo3/GCN) displays effective H2 generation under visible light, with TOF metrics on par with those of its homogeneous analog. Although substantial leaching of [Mo3S13]2- species from the Mo3/GCN surface occurs, the remaining {Mo3}-based centers demonstrate impressive stability, leading to enduring HER performance, starkly distinguishing it from the homogeneous Mo3/Ru photosystem. Photoluminescence (PL) quenching experiments confirm that the performance of Mo3/GCN is not limited by the quality of the inorganic interface, but could be optimized by using higher surface area supports or a higher concentration of [Mo3S13]2- sites. Our findings showcase complexities underlying the evaluation and comparison of photosystems comprising well-defined catalytic centers and pave the way for developing analogous surface-supported (photo)catalysts with broad use in energy applications.

5.
J Mater Chem C Mater ; 10(45): 17048-17052, 2022 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-36561542

RESUMO

We report two Ni12 multicubane topologies enclosed in the polyanions [Ni12(OH)9(WO4)3(PO4)(B-α-PW9O34)3]21-{Ni12W30} and [Ni12(OH)9(HPO4)3(PO4)(B-α-PW9O34)(A-α-PW9O34)2]21-{Ni12W27} that magnetically behave as Ni12 units clearly distinguishing them from typical Ni4 cubanes as shown by magnetic studies together with high field and frequency electron paramagnetic resonance (HFEPR). Beyond the unprecedented static properties, {Ni12W30} shows the unusual coexistence of slow relaxation of the magnetization and a diamagnetic ground state (S = 0), providing the unique opportunity of studying the essentially elusive magnetic relaxation behavior in excited states. The cubane-topology dependent activity of {Ni12W30} and {Ni12W27} as homogeneous HER photocatalysts unveils the structural key features significant for the design of photocatalysts with efficient charge utilization exemplified by high quantum yields (QY) of 10.42% and 8.36% for {Ni12W30} and {Ni12W27}, respectively.

6.
ACS Catal ; 12(11): 6641-6650, 2022 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-35692252

RESUMO

Achieving light-driven splitting of water with high efficiency remains a challenging task on the way to solar fuel exploration. In this work, to combine the advantages of heterogeneous and homogeneous photosystems, we covalently anchor noble-metal- and carbon-free thiomolybdate [Mo3S13]2- clusters onto photoactive metal oxide supports to act as molecular co-catalysts for photocatalytic water splitting. We demonstrate that strong and surface-limited binding of the [Mo3S13]2- to the oxide surfaces takes place. The attachment involves the loss of the majority of the terminal S2 2- groups, upon which Mo-O-Ti bonds with the hydroxylated TiO2 surface are established. The heterogenized [Mo3S13]2- clusters are active and stable co-catalysts for the light-driven hydrogen evolution reaction (HER) with performance close to the level of the benchmark Pt. Optimal HER rates are achieved for 2 wt % cluster loadings, which we relate to the accessibility of the TiO2 surface required for efficient hole scavenging. We further elucidate the active HER sites by applying thermal post-treatments in air and N2. Our data demonstrate the importance of the trinuclear core of the [Mo3S13]2- cluster and suggest bridging S2 2- and vacant coordination sites at the Mo centers as likely HER active sites. This work provides a prime example for the successful heterogenization of an inorganic molecular cluster as a co-catalyst for light-driven HER and gives the incentive to explore other thio(oxo)metalates.

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