Endowed with flexible surface coordination and synergetic electronic status, bimetallic particles serve as promising heterogeneous catalysts as their microstructures evolved sensitively to the treatment atmospheres, whereas knowledge of dynamic manners is less. Herein, utilizing environmental transmission electron microscopy (ETEM), the reconstructions of Cu3Pd particles in oxidation/reduction atmospheres were explored at atomic scale. Specifically, bare Cu3Pd particles went through a phase separation of CuO and PdO during in situ oxidation, and subsequent agglomeration after H2 reduction. While protected in a silica shell, the confined Cu3Pd particles were oxidized into Cu1.5Pd0.5O2 phase after air calcination and subsequently restructured into versatile configurations during reduction. Specifically, hollow Cu3Pd alloy architecture with Pd enriched layer near surface as reduced at 200 oC. Further rising 400 to 600 oC, it yielded disordered Cu3Pd alloys with slightly Pd atoms enrichment at outmost surface. The dynamical behaviors of single Cu1.5Pd0.5O2 particle during in situ reduction have been visualized in ETEM, wherein a series of deformation, elongation and rotation is involved during the hollow architecture firstly formation, and then vanished into a Cu3Pd solid solution nanoparticle. The tunable microstructures of Cu3Pd@SiO2 driven by redox atmospheres demonstrate efficient approach for precisely regulating the chemical environments of constrained bimetallic nanocatalysts.

The investigation delves into the functionality exhibited by ferroelectric BiFe0.95Mn0.05O3 (BFM) nanoparticles (NPs) concerning the hydrogen evolution reaction (HER). The electrocatalytic activity of BFM NPs undergoes a transformative shift as a consequence of mono-, di-, and tri-valent cation substitution. Notably, the strategic engineering of doping at the Bi site within BFM NPs yields a remarkable outcome, namely the conspicuous reduction of the kinetic overpotential prerequisite for HER. This diminished overpotential in doped BFM NPs arises from the confluence of multifarious factors: diminished charge transfer resistance, augmented specific surface area, a discernible distribution of pore sizes ranging from narrow to broad, particles endowed with a shape boasting abundant active facets, and the integration of dopants as novel active sites on the surface. Furthermore, the presence of surface defects, oxygen vacancies, and amplified microstrain within doped BFM NPs contributes to the reduction in overpotential.

Synthetic photochemistry is a research field, where organic transformations are promoted by the presence of photoactive species, under light irradiation. In particular, the sub-field of photo-organocatalysis, where organic molecules are used as photocatalysts, has been launched as a “green” and sustainable approach. Carbon allotrope nanostructures (CANs) and their derivatives exhibit unique photophysical and photochemical properties, which have been exploited for the preparation of efficient metal-free and sustainable photocatalytic systems. This review summarizes the progress on the field of photochemical carbocatalysis, presenting the achievements by fullerene-, carbon nanotube- and graphene-based nanomaterials. Additionally, future prospects for CAN-based nanomaterials as photochemical promoters for organic transformations are also mentioned.

Aspergillus niger rutinosidase (AnRut) efficiently cleaved a library of rutin glycomimetics - isoquercitrin acylated at C-6′ of its glucosyl moiety. The substrates tested included isoquercitrin substituted at glucosyl C-6′ with acetyl, benzoyl, phenylacetyl, phenylpropanoyl, cinnamyl, vanillyl, galloyl, 4-hydroxybenzoyl, and 3-(4-hydroxy-3-O-methylphenyl)propanoyl. AnRut showed the ability to transglycosylate with the substrates 6′-O-acetyl isoquercitrin and 6′-O-benzoyl isoquercitrin substrates, affording n-butyl 6-acetyl-β-d-glucopyranoside and n-butyl 6-benzoyl-β-d-glucopyranoside.

Abstract

Rutinosidase is a diglycosidase that catalyzes the cleavage of rutinose (α-l-Rhap-(1→6)-β-d-Glcp) from rutin or other rutinosides. It is also able to cleave β-glucopyranosides, e. g., isoquercitrin. This enzyme has a strong transglycosylation activity and a remarkable substrate specificity. We have shown that rutinosidase from Aspergillus niger (AnRut) is able to cleave β-glucopyranosides acylated at C-6 of glucose (6′-O-acylisoquercitrin) with acetyl, benzoyl, phenylacetyl, phenylpropanoyl, cinnamoyl, vanillyl, galloyl, 4-hydroxybenzoyl and 3-(4-hydroxy-3-methoxyphenyl)propanoyl. The release of the respective 6-acylglucopyranoses was confirmed by HPLC/MS and NMR methods. Selected compounds, i. e., 6′-O-acetyl, 6′-O-benzoyl, and 6′-O-cinnamyl derivatives of isoquercitrin, were also tested as transglycosylation substrates. Only 6′-acetylisoquercitrin and 6′-O-benzoylisoquercitrin underwent transglycosylations by AnRut to produce n-butyl 6-acetyl-β-d-glucopyranoside and n-butyl 6-benzoyl-β-d-glucopyranoside. Isoquercitrin 6′-O-cinnamate yielded on hydrolytic product. Molecular modeling based on the crystal structure of AnRut showed that large aromatic moieties at C-6′ of isoquercitrin block the side tunnel of AnRut leading into its active site and thus hinder the entry of the acceptor substrate for transglycosylation. This study demonstrates the great substrate flexibility of rutinosidase at the glycone site.

Silicon-based and silicon-containing materials have been used in polymer electrolyte membrane fuel cells (PEMFCs), solid oxide fuel cells (SOFCs) and phosphoric acid fuel cells (PAFCs). In this work the use of silicon in the membrane electrode assembly (MEA) of fuel cells is reviewed.

Abstract

Silicon, silicon-based and Si-containing materials are widely used and play different roles in fuel cells. These materials have been used overall in polymer electrolyte membrane fuel cells, but also in solid oxide fuel cells and phosphoric acid fuel cells. The most used Si compounds in fuel cells are SiO₂ and SiC. In this work an overview of the use of Si-based and Si-containing materials in the membrane electrode assembly of fuel cells is presented.

This review analyzes the literature data and the results of studies of the Pt/CeO₂ based catalysts which capable of providing the low-temperature CO oxidation. In this review the catalytic characteristics, local structure of active sites and charge state of platinum and ceria in catalysts, that is necessary for the low-temperature oxidation at T<50 °C, are summarized.

Abstract

This review analyzes the literature data and the results of studies of the Pt/CeO₂-based catalysts that are capable of providing the low-temperature CO oxidation (LTO CO). The review summarizes the catalytic characteristics and the main properties of Pt/CeO₂-based catalysts necessary for the low-temperature oxidation at T<50 °C. Analysis of the literature data on the use of physical methods of investigation and their correlation with the activity of Pt/CeO₂ catalysts allowed us to conclude that the main active forms of platinum are small metallic clusters, single atoms Pt²⁺-SA and oxide clusters PtO_x interacting with ceria nanoparticles. It has been established that the most active forms are PtO_x clusters, which provide a high reaction rate in the temperature range from −50 to +50 °C. Forms of ionic Pt²⁺ with different coordination with oxygen ensure the activity of catalysts starting at temperatures above 100 °C. Finally, small metallic clusters occupy an intermediate position, providing activity above 0 °C, but their instability and gradual transition to the oxidized state Pt²⁺/PtO_x are noted. At the conclusion of the review, the results of mathematical modeling demonstrate the correct kinetics description of the low-temperature CO oxidation based on the Mars-van Krevelen and associative mechanisms.

Biocarbon catalysts were prepared from iron and nickel impregnated pyrolyzed fern and willow to mimic plants issued from phytoremediation. Reverse water-gas shift (RWGS) catalyzed by these catalysts was studied at 400 °C and H₂/CO₂=3 as RWGS can partake in Fischer-Tropsch synthesis to form synthetic fuel. They were highly selective (>84 %) with fair conversion (<17 %) and showed no long-use (288 h) deactivation.

Abstract

Biocarbon catalysts for reverse water-gas shift reaction (RWGS) were produced from pyrolyzed fern and willow impregnated with iron and nickel nitrates. This reaction can partake during Fischer-Tropsch synthesis (FTS) by consuming CO₂ and lowering both the H₂/CO ratio and the efficiency in the production of fuels. RWGS has attracted much attention to widespread utilization of CO₂ through the production of syngas. The catalysts were therefore tested in a fixed-bed reactor at 400 °C as it is the maximal temperature for FTS and high RWGS. They showed high selectivity towards CO (>84 %) and fair conversion (<17 %) compared to rust (81 %, 30 %, respectively) and Fe-impregnated alumina (100 %, 8 %). No loss in selectivity and conversion was observed for a longer residence time (288 h). Biomass inherent metals could provide reactive gas adsorption sites that improve conversion by dispersing electrons which reduces adsorption and dissociation energy barriers. K, Mg and Ca in fern biocarbon catalysts may be related to the higher CO₂ uptake compared to willow catalysts. Electron deficient sites produced by reduction of biocarbon oxygen functional groups may facilitate CO₂ uptake and activation. Ni-impregnated fern-based biocarbon showed the highest activity, due to the synergetic effect of the inherent metals, O vacancies and strong metal-carbon interactions.

Two-dimensional boron nanosheets (borophene) exhibit promising catalytic properties for energy and environmental applications. This review summarizes the theoretical and experimental applicability of borophene and its heterostructures towards efficient hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), CO₂ reduction reaction (CO₂RR), N₂ reduction reaction (N₂RR), photocatalytic degradation, etc.

Abstract

Borophene, a new member of the two-dimensional (2D) materials family, has attracted researchers since its first experimental synthesis. Borophene (2D boron nanosheet) differs significantly from other 2D materials due to its low energy requirement to form defects, anisotropy, electron-deficient structure, multicentered bonding, etc. The uniqueness in properties of borophene compared to other 2D materials makes it suitable for applications in catalysis, sensing, energy storage, etc. The present review summarizes the development of borophene synthesis and emphasizes its applications in catalysis. Different synthesis approaches and their advantages and limitations are discussed briefly as substantial reviews are available on borophene synthesis. The applications of pristine borophene and their modified heterostructure in the field of catalysis were thoroughly reviewed, focusing on the electrocatalysis applications. Finally, the review discussed the future scope of borophene in designing new materials as well as opportunities to be utilized for other application fields. Since there is a lack of a good number of experimental reports on the applications of borophene and its derivatives, a huge opportunity is waiting for the researchers to explore the unknown world of borophene. In this regard, this review will help the researchers in an excellent manner.

Solution combustion is an efficient, simple and fast method to prepare oxygen carriers for the chemical looping reforming of methane, which can yield oxygen carriers with high reactivity and excellent cyclic stability.

Abstract

Efficient activation and the conversion of methane to value-added products have long attracted interest. Chemical looping reforming has become a competitive technology to transform methane into syngas that can act as raw material for various chemicals. In this paper, the methane chemical looping reforming reactivity of the Ce−Co composite oxygen carriers fabricated with different preparation methods, including solution combustion, ball-milling, hydrothermal, and co-precipitation method, are investigated on a fixed-bed. Various bulk/surface characterizations (TEM, XRD, BET, XPS, Raman, etc.) were applied to reveal the effect of preparation methods on the properties of these oxygen carriers. The results indicate that the oxygen carrier prepared by the solution combustion method exhibits excellent methane conversion, high syngas yield, and desirable H₂/CO ratio, as well as stable regenerability because of its relatively small crystal size, large specific surface area, high oxygen vacancy concentration and Ce³⁺/Ce⁴⁺ ratio. This work may be helpful in the preparation of highly active and stable oxygen carriers for chemical looping reforming reaction of methane.

Photocatalytic water splitting via two-electron pathway offers a more fascinating and kinetically favorable way to produce H₂ compared with traditional four-electron pathway. The review highlights the mechanism and advancements of photocatalytic H₂ production via a two-electron pathway. Additionally, it addresses the challenges and opportunities for the commercial application of photocatalytic water splitting via the two-electron pathway.

Abstract

In response to energy and environmental crises, solar-driven pure water splitting is a promising way to produce and store renewable energy sources without environmental pollution. Photocatalytic water splitting via two-electron pathway (2H₂O→H₂+H₂O₂) is a more kinetically favorable way to produce H₂ compared with traditional four-electron pathway. Although numerous efforts have been devoted to investigate the application of two-electron pathway water splitting, drawbacks still inhibit the efficiency of H₂ generation. This review discusses the mechanism and challenges of photocatalytic water splitting via a two-electron pathway. Then, recent developments in novel photocatalyst preparation and modification strategies for effective H₂ generation via two-electron pathway were discussed, such as morphology and structure modulation, elemental doping, co-catalyst loading, and heterostructure construction. In addition, the development of stepwise two-electron pathway which further decomposed H₂O₂ and release O₂ was also introduced. Appropriate co-catalyst with high H₂O₂ decomposition activity that is essential for stepwise process was discussed. Finally, challenges and opportunities for commercial application of photocatalytic water splitting via two-electron pathway were briefly outlined.