The effect of different exposed facets on the photoelectrocatalytic degradation of o-chlorophenol using p-type Cu 2 O crystals

Long-lifetime water-washable ceramic catalyst filter for air purification

Particulate matter (PM) and volatile organic compounds (VOCs) are recognised as hazardous air pollutants threatening human health. Disposable filters are generally used for air purification despite frequent replacement and waste generation problems. However, the development of a novel regenerable and robust filter for long-term use is a huge challenge. Here, we report on a new class of facile water-washing regenerable ceramic catalyst filters (CCFs), developed to simultaneously remove PM (>95%) and VOCs (>82%) in single-pass and maximized space efficiency by coating the inner and outer filter channels with an inorganic membrane and a Cu₂O/TiO₂ photocatalyst, respectively. The CCFs reveal four-fold increase in the maximum dust loading capacity (approximately 20 g/L) in relation to conventional filters (5 g/L), and can be reused after ten regeneration capability with simple water washing retaining initial PM and VOC removal performances. Thus, the CCFs can be well-suited for indoor and outdoor air purification for 20 years, which shows a huge increase in lifetime compared to the 6-month lifespan of conventional filters. Finally, we believe that the development and implementation of CCFs for air purification can open new avenues for sustainable technology through renewability and zero-waste generation.

Chemical conversion based on the crystal facet effect of transition metal oxides and construction methods for sharp-faced nanocrystals

In-depth research has found that the nanocrystal facet of transition metal oxides (TMOs) greatly affects their heterogeneous catalytic performance, as well as the property of photocatalysis, gas sensing, electrochemical reaction, etc. that are all involved in chemical conversion processes. Therefore, the facet-dependent properties of TMO nanocrystals have been fully and carefully studied by combining systematic experiments and theoretical calculations, and mechanisms of chemical reactions are accurately explained at the molecular level, which will be closer to the essence of reactions. Evidently, as an accurate investigation on crystal facets, well-defined TMO nanocrystals are the basis and premise for obtaining relevant credible results, and shape-controlled synthesis of TMO nanocrystals thereby has received great attention and development. The success in understanding of facet-dependent properties and shape-controlled synthesis of TMO nanocrystals is highly valuable for the control of reaction and the design of high-efficiency TMO nanocrystal catalysts as well as other functional materials in practical applications.

Strategies for Improved Electrochemical CO2 Reduction to Value-added Products by Highly Anticipated Copper-based Nanoarchitectures

Uncontrolled CO₂ emission from various industrial and domestic sources is a considerable threat to environmental sustainability. Scientists are trying to develop multiple approaches to not only reduce CO₂ emissions but also utilize this potent pollutant to get economically feasible products. The electrochemical reduction of CO₂ (ERC) is one way to effectively convert CO₂ to more useful products (ranging from C1 to C5). Nevertheless, this process is kinetically hindered and less selective towards a specific product and, consequently, requires an efficient electrocatalyst with characteristics like selectivity, stability, reusability, low cost, and environmentally benign. Owing to specified commercial features, copper (Cu)-based materials are highly anticipated and widely investigated for the last two decades. However, their non-modified polycrystalline Cu forms usually lack selectivity and lower overpotential of CO₂ reduction. Therefore, extensive research is in progress to induce various alterations ranging from morphological and surface chemistry tuning to structural and optoelectrical characteristics modifications. This review provides an overview of those strategies to improve the CO₂ conversion efficiency through Cu-based ERC into valuable C1, C2_, and higher molecular weight hydrocarbons. The thermodynamics and kinetics of CO₂ reduction via Cu-based electrocatalysts are discussed in detail with the support of the first principle DFT-based models. In the last portion of the review, the reported mechanisms for various products are summarized, with a short overview of the outlook. This review is expected to provide important basics as well as advanced information for experienced as well as new researchers to develop various strategies for Cu and related materials to achieve improved ERC.

Smart Bifunctional Sb2 Se3 Nanorods for Integrated Water Purification: Insoluble Liquid Separation and Photoelectrochemical Degradation

Antimony selenide (Sb₂ Se₃ ) nanostructures enable bifunctional water purification by a single membrane through i) physical separation of water-insoluble oil and ii) photoelectrocatalytic degradation of water-soluble organic compounds. Sb₂ Se₃ nanorods with exposed surfaces of {h 0 0} and {h 0 l} planes exhibit superhydrophobicity (water contact angle of ≈159°) owing to extremely low surface energy of those dangling-bond-free van der Waals planes. Based on crystallographic understanding, superhydrophobic Sb₂ Se₃ nanorods were produced on a mesh-type substrate for utilization as a membrane for physical water/oil separation. Sb₂ Se₃ exhibited an optimal photocathodic response with p-type electrical conductivity under visible light along the longitudinal crystal direction. This indicated that the nanorods could be used as photoelectrocatalytic material for chemical water purification. A smart membrane with Sb₂ Se₃ nanostructures was proposed as a candidate for integrated water purification that can simultaneously accomplish water/oil separation and photoelectrocatalytic degradation of organic compounds in wastewater. Linear sweep voltammetry measurements of the Sb₂ Se₃ -membrane showed cathodic photocurrent generation (up to approximately 10 mA cm^-2 at 0 V vs. reversible hydrogen electrode), which was enough to reduce O₂ to an oxygen radical (O₂ ^.- ) for degradation of methyl orange. Consequently, solar-driven integrated water purification was demonstrated for the first time by using a single material with a dual function of superhydrophobicity and photoactivity.

Effect of the supports on catalytic activity of Pd catalysts for liquid-phase hydrodechlorination/hydrogenation reaction

Carbon nanotubes (CNTs), activated carbon (AC), graphene, and aluminum oxide (Al₂O₃) supported 5% Pd catalysts were prepared by the conventional impregnation method, and catalytic activity was tested in the hydrogenation of 4-chlorophenol (4-CP) and nitrobenzene (NB) under ambient conditions (313 K and atmospheric pressure). It was found that catalytic activity was greatly affected by the supports. Moreover, Pd/CNTs catalyst exhibited much higher catalytic activity than the other three supported Pd catalysts. The mechanism of this phenomenon was studied through catalyst characterization (ICP-MS, Brunauer-Emmett-Teller [BET], TEM, and SEM). It was found that the mean particle size of Pd nanoparticles for Pd/CNTs (4.3 nm) was smaller than that for Pd/AC (6.9 nm), Pd/Al₂O₃ (5.0 nm), and Pd/graphene (5.2 nm). Moreover, the actual loading amounts of Pd and BET surface areas were not the main reasons for the different catalytic activity of the four supported Pd catalysts. Above all, the smaller Pd particles of Pd/CNTs enabled the Pd/CNTs catalyst to exhibit much higher catalytic activity for the hydrogenation reactions.

Crystal Facet Engineering of Photoelectrodes for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting is a promising approach for solar-driven hydrogen production with zero emissions, and it has been intensively studied over the past decades. However, the solar-to-hydrogen (STH) efficiencies of the current PEC systems are still far from the 10% target needed for practical application. The development of efficient photoelectrodes in PEC systems holds the key to achieving high STH efficiencies. In recent years, crystal facet engineering has emerged as an important strategy in designing efficient photoelectrodes for PEC water splitting, which has yet to be comprehensively reviewed and is the main focus of this article. After the Introduction, the second section of this review concisely introduces the mechanisms of crystal facet engineering. The subsequent section provides a snapshot of the unique facet-dependent properties of some semiconductor crystals including surface electronic structures, redox reaction sites, surface built-in electric fields, molecular adsorption, photoreaction activity, photocorrosion resistance, and electrical conductivity. Then, the methods for fabricating photoelectrodes with faceted semiconductor crystals are reviewed, with a focus on the preparation processes. In addition, the notable advantages of the crystal facet engineering of photoelectrodes in terms of light harvesting, charge separation and transfer, and surface reactions are critically discussed. This is followed by a systematic overview of the modification strategies of faceted photoelectrodes to further enhance the PEC performance. The last section summarizes the major challenges and some invigorating perspectives for future research on crystal facet engineered photoelectrodes, which are believed to play a vital role in promoting the development of this important research field.

Synthesis and phase transformation of NaGdF4:Yb–Er thin films using electro-deposition method at moderate temperatures

Herein, a thin film of hexagonal-phase NaGdF₄:Yb–Er is fabricated by electro-deposition at moderate temperatures. The phase of NaGdF₄:Yb–Er thin film can be controlled by adding PVP in the electrolyte.