Engineering a NiAl-LDH/CoSx S-Scheme heterojunction for enhanced photocatalytic hydrogen evolution

Tannic Acid Selective Modulation Defects to Enhance the Photocatalytic CO2 Reduction Activity of Layered Double Hydroxides

Recently, layered double hydroxides (LDH) have shown great potential in photoreduction of CO2 owing to its flexible structural adjustability. In this study, the mild acidic property of tannic acid (TA) is exploited to etch the bimetal LDH to create abundant vacancies to gain the coordination unsaturated active centers. Based on the different chelating abilities of TA to various metal ions, the active metals are remained by selective chelation while the inert metals are removed during the etching process of bimetal LDH. Furthermore, selective chelating with metal ions not only increases the percentage of highly active metals but also compensates for the structural damage caused by the etch, which achieves a scalpel-like selective construction of vacancies. The NiAl-LDH etched and functionalized by TA for 3 h exhibits superior photo-reduction of CO2 performance without co-catalysts and photo-sensitizers, which is 14 times that of the pristine NiAl-LDH. The fact that many bimetal LDHs can be functionalized by TA and exhibit significantly improved photocatalytic efficiency is confirmed, suggesting this strategy is generalized to functionalize double- or multi-metal LDH. The method provided in this work opens the door for polyphenol-functionalized LDHs to enhance their ability for light-driven chemical transformations.

Tailored Engineering of Layered Double Hydroxide Catalysts for Biomass Valorization: A Way Towards Waste to Wealth

Layered double hydroxides (LDH) have significant attention in recent times due to their unique characteristic properties, including layered structure, variable compositions, tunable acidity and basicity, memory effect, and their ability to transform into various kinds of catalysts, which make them desirable for various types of catalytic applications, such as electrocatalysis, photocatalysis, and thermocatalysis. In addition, the upcycling of lignocellulose biomass and its derived compounds has emerged as a promising strategy for the synthesis of valuable products and fine chemicals. The current review focuses on recent advancements in LDH-based catalysts for biomass conversion reactions. Specifically, this review highlights the structural features and advantages of LDH and LDH-derived catalysts for biomass conversion reactions, followed by a detailed summary of the different synthesis methods and different strategies used to tailor their properties. Subsequently, LDH-based catalysts for hydrogenation, oxidation, coupling, and isomerization reactions of biomass-derived molecules are critically summarized in a very detailed manner. The review concludes with a discussion on future research directions in this field which anticipates that further exploration of LDH-based catalysts and integration of cutting-edge technologies into biomass conversion reactions hold promise for addressing future energy challenges, potentially leading to a carbon-neutral or carbon-positive future.

Carbon-Dots-Modified Hierarchical ZnIn2S4/Ni-Al LDH Heterojunction with Boosted Charge Transfer for Visible-Light-Driven Photocatalytic H2 Evolution

The construction of a heterojunction structure is considered a significant route to promote solar-driven H₂ production. Herein, a CDs/ZnIn₂S₄/Ni-Al LDHs (CDZNA) ternary heterojunction was elaborately constructed via the in situ growth of ZnIn₂S₄ on Ni-Al LDHs with the incorporation of carbon dots (CDs) cocatalyst, which was used as a highly efficient catalyst for the photocatalytic H₂ generation. Characterizations indicated that 2D ZnIn₂S₄ nanosheet homogeneously dispersed on the surface of Ni-Al LDHs fabricated an intimate hierarchical architecture and provided a high BET surface area (135.12 m² g^-1). In addition, the unique embeddable-dispersed CDs as electron mediators possessed numerous active sites and promoted the charge separation on ZnIn₂S₄/Ni-Al LDHs (ZNA) binary catalyst. By coupling these two features, the CDZNA catalyst exhibited a considerable H₂ production rate of 23.1 mmol g^-1 h^-1 under visible-light illumination, which was 16.4 and 1.4 times higher than those of ZnIn₂S₄ and ZNA, respectively. A proposed mechanism of photocatalytic H₂ production over the CDZNA catalyst was also discussed. This work provides a promising strategy to achieve highly efficient solar energy conversion in a ternary photocatalytic system.

Dual-sensitized heterojunction PDA/ZnO@MoS2 QDs combined with multilocus domino-like DNA cascade reaction for ultrasensitive photoelectrochemical biosensor

In this work, by integrating with a highly efficient multilocus domino-like cascade reaction on DNA nanonet, an ultrasensitive PEC biosensor based on dual-sensitized PDA/ZnO@MoS₂ QDs photoactive material as signal probe was proposed for detection of miRNA-182-5p. The dual-sensitized PDA/ZnO@MoS₂ QD composed by both of p-n and S-scheme heterojunctions on electrode generated an extremely high initial PEC signal, which however quenched by CdTe QDs decorated on DNA nanonet owing to the significant p-n quenching effect. Thereafter, the output DNA (RS) from DSN enzyme-assisted target recycling amplification triggered an ingenious multilocus domino-like DNA cascade reaction on DNA nanonet for releasing numerous CdTe QDs. Thanks to the multilocus domino-like mode that owned abundant binding sites for increasing trigger efficiency and drove cascade reaction automatically advance along four stated pathways, the target conversion rate could be improved effectively compared with that of traditional approaches, significantly enhancing the detection sensitivity. Consequently, the developed PEC biosensor exhibited a low detection limit to 0.17 fM, providing a new avenue for sensitive, fast and reliable sensing of various DNA/RNA.

Step scheme nickel-aluminium layered double hydroxides/biochar heterostructure photocatalyst for synergistic adsorption and photodegradation of tetracycline

Improving the adsorption ability of layered double hydroxide (LDH) has been considered as a promising strategy to promote its photodegradation of aqueous pollutants. In this work, nickel-aluminium layered double hydroxides (NiAl-LDH)/biochar nanocomposites were prepared using a simple coprecipitation method, and then applied in synergistic adsorption-photodegradation of tetracycline (TC) in aqueous solutions. In addition, the governing TC removal mechanisms by the nanocomposites were revealed. All NiAl-LDH/BC samples showed strong adsorption and photodegradation of TC. The Langmuir maximum TC adsorption capacity of optimized NiAl-LDH/BC-0.5 reached 124.2 mg/g, which was much better than that of NiAl-LDH (56.1 mg/g) and biochar (11.1 mg/g). Besides, TC photodegradation rate constant of NiAl/BC-0.5 was 3.6 and 4.4 times of that of NiAl-LDH and BC, respectively. The NiAl/BC-0.5 exhibited the maximum TC adsorption-photodegradation efficiency 94.4% in 90 min compared to NiAl-LDH (73.7%) and BC (48.2%). The rate constant of modified Elovich kinetic model for synergistic adsorption and photodegradation on NiAl/BC-0.5 (9.477 min^-1) was the highest among the composites. The NiAl-LDH/BC had significantly larger BET surface areas than NiAl-LDH and BC. The step scheme (S-scheme) heterostructures were constructed on the interface of BC and NiAl-LDH in nanocomposites, which facilitated the transfer of photo-induced charges. This work demonstrates that combination of NiAl-LDH and biochar can create synergy for TC adsorption-photodegradation, which is a promising and green strategy.

Plasma-Assisted Fabrication of Molecularly Imprinted NiAl-LDH Layer on Ni Nanorod Arrays for Glyphosate Detection

An inorganic-framework molecularly imprinted NiAl layered double hydroxide (MI-NiAl-LDH) with specific template molecule (glyphosate pesticide, Glyp) recognition ability was prepared on Ni nanorod arrays (Ni NRAs) through electrodeposition followed by a low-temperature O₂ plasma treatment. The freestanding Ni/MI-NiAl-LDH NRA electrode had highly enhanced sensitivity and selectivity. The electrocatalytic oxidation of Glyp was proposed to occur at Ni³⁺ centers in MI-NiAl-LDH, and the current response depended linearly on the Glyp concentration from 10.0 nmol/L to 1.0 μmol/L (R² = 0.9906), with the limit of detection (LOD) being 3.1 nmol/L (S/N = 3). An exceptional discriminating capability with tolerance for other similar organophosphorus compounds was achieved. Molecular imprinting (N and P residues) affected the electronic structure of NiAl-LDH, triggering the formation of highly active NiOOH sites at relatively lower anodic potentials and substantially enhancing the electrocatalytic oxidation ability of the NiAl-LDH interface toward the C-N bonds in Glyp. In combination with the surface enrichment effect of MI-NiAl-LDH toward template molecules, the electrochemical oxidation signal intensity of Glyp increased significantly, with a greater peak separation from interfering molecules. These results challenge the common belief that the excellent performance of inorganic-framework molecularly imprinted interfaces arises from their specific adsorption of template molecules, providing new insight into the development of high-performance organic-pollutant-sensing electrodes.