The main contributions in the field of first-row transition-metal-catalyzed (base-metal-catalyzed) carbonylative transformations have been summarized and discussed. The contents have been divided ...according to the electrophiles applied, followed by the different types of nucleophiles. Their reaction mechanisms and applications have been emphatically discussed.
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IJS, KILJ, NUK, PNG, UL, UM
2D materials show many particular properties, such as high surface‐to‐volume ratio, high anisotropic degree, and adjustable chemical functionality. These unique properties in 2D materials have ...sparked immense interest due to their applications in photocatalytic systems, resulting in significantly enhanced light capture, charge‐transfer kinetics, and surface reaction. Herein, the research progress in 2D photocatalysts based on varied compositions and functions, followed by specific surface modification strategies, is introduced. Fundamental principles focusing on light harvesting, charge separation, and molecular adsorption/activation in the 2D‐material‐based photocatalytic system are systemically explored. The examples described here detail the use of 2D materials in various photocatalytic energy‐conversion systems, including water splitting, carbon dioxide reduction, nitrogen fixation, hydrogen peroxide production, and organic synthesis. Finally, by elaborating the challenges and possible solutions for developing these 2D materials, the review is expected to provide some inspiration for the future research of 2D materials used on efficient photocatalytic energy conversions.
Although the research of 2D photocatalysts has made great progress in the past decades, there are still many challenges in understanding the deep relationship between the surface state and the reaction mechanism. The surface modification strategies and reaction mechanisms of 2D photocatalysts are reviewed, and some useful views are put forward for future research in this field.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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bstract
Signals of heavy particle production during inflation are encoded as nonanalytic momentum scaling in primordial non-Gaussianity. These non-analytic signatures can be sourced by Standard ...Model particles with a modified Higgs scale uplifted by the slow-roll dynamics of inflation. We show that such a lifting mechanism becomes more efficient with the presence of a strong Higgs-inflaton mixing, where the Higgs mass scale is further increased by a small speed of sound in the effective theory of inflation. As a primary step towards detecting new particles in the cosmological collider program, non-Gaussianity due to heavy Higgs production in the strong-mixing regime can act as important background signals to be tested by future cosmological surveys.
Highly efficient electrocatalysts are essential for the production of green hydrogen from water electrolysis. Herein, a metal‐organic framework‐assisted pyrolysis‐replacement‐reorganization approach ...is developed to obtain ultrafine Pt‐Co alloy nanoparticles (sub‐10 nm) attached on the inner and outer shells of porous nitrogen‐doped carbon nanotubes (NCNT) with closed ends. During the thermal reorganization, the migration of Pt‐Co nano‐alloys to both surfaces ensures the maximized exposure of active sites while maintaining the robust attachment to the porous carbon matrix. Density functional theory calculations suggest a nearly thermodynamically‐neutral free energy of adsorption for hydrogen intermediates and diversified active sites induced by alloying, thus resulting in a great promotion in intrinsic activity towards the hydrogen evolution reaction (HER). Benefiting from the delicate structural design and compositional modulation, the optimized Pt3Co@NCNT electrocatalyst manifests outstanding HER activity and superior stability in both acidic and alkaline media.
Ultrafine Pt‐Co alloy nanoparticles confined on the inner and outer surfaces of porous nitrogen‐doped carbon nanotubes (Pt‐Co@NCNT) have been synthesized through a metal–organic framework (MOF)‐assisted pyrolysis‐replacement‐reorganization approach. With the structural and compositional merits, the Pt3Co@NCNT electrocatalyst presents superior activity and stability in both acidic and alkaline media for the hydrogen evolution reaction.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The development of low‐cost, high‐efficiency, and robust electrocatalysts for the oxygen evolution reaction (OER) is urgently needed to address the energy crisis. In recent years, ...non‐noble‐metal‐based OER electrocatalysts have attracted tremendous research attention. Beginning with the introduction of some evaluation criteria for the OER, the current OER electrocatalysts are reviewed, with the classification of metals/alloys, oxides, hydroxides, chalcogenides, phosphides, phosphates/borates, and other compounds, along with their advantages and shortcomings. The current knowledge of the reaction mechanisms and practical applications of the OER is also summarized for developing more efficient OER electrocatalysts. Finally, the current states, challenges, and some perspectives for non‐noble‐metal‐based OER electrocatalysts are discussed.
This review summarizes the evaluation criteria, recent advancements of non‐noble‐metal‐based electrocatalysts, reaction mechanisms, and some practical applications of the oxygen evolution reaction (OER). Although great strides have been made in the past decades, the current state of non‐noble‐metal‐based OER electrocatalysts is still facing many challenges, which are discussed together with some useful perspectives and future directions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The oxygen evolution reaction (OER) acts as the bottleneck of some crucial energy conversion and storage technologies involving water electrolysis, CO2 electrolysis, and metal‐air batteries, among ...others. The challenging sluggish reaction kinetics of the OER can be overcome via developing highly efficient electrocatalysts, which experience a dynamic structural evolution process during the reaction. However, the reaction mechanism of the structural transformation of electrocatalysts during the OER and the structure‐activity correlation in understanding the real active sites remain elusive. Fortunately, operando characterizations offer a platform to study the structural evolution processes and the reaction mechanisms of OER electrocatalysts. In this review, using several in situ/operando techniques some recent advances are elaborated with emphases on tracking the structural evolution processes of electrocatalysts, recording the reaction intermediates during electrocatalysis, and building a link between the structure and activity/stability of electrocatalysts. Moreover, theoretical considerations are also discussed to assist operando characterization understanding. Finally, some perspectives are provided which are expected to be helpful to tackle the current challenges in operando monitoring and unraveling the reaction mechanisms of OER electrocatalysts.
This review summarizes the recent advances in operando characterization of oxygen evolution electrocatalysts and its role in helping improve understanding of structural evolution processes and reaction mechanisms. The development of oxygen evolution reaction electrocatalysts is still facing many challenges, which are discussed and elaborated in detailed examples together with some useful perspectives for future studies in the field.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The development of efficient and low‐cost electrocatalysts toward the oxygen evolution reaction (OER) is critical for improving the efficiency of several electrochemical energy conversion and storage ...devices. Here, we report an elaborate design and synthesis of porous Co‐based trimetallic spinel oxide nanoboxes (NiCo2−xFexO4 NBs) by a novel metal‐organic framework engaged strategy, which involves chemical etching, cation exchange, and subsequent thermal oxidation processes. Owing to the structural and compositional advantages, the optimized trimetallic NiCo2−xFexO4 NBs (x is about 0.117) deliver superior electrocatalytic performance for OER with an overpotential of 274 mV at 10 mA cm−2, a small Tafel slope of 42 mV dec−1, and good stability in alkaline electrolyte, which is much better than that of Co‐based bi/monometallic spinel oxides and even commercial RuO2.
Co‐based trimetallic spinel oxide nanoboxes are synthesized through an elaborate strategy involving chemical etching, cation exchange and thermal oxidation processes. The unique structural and compositional advantages endow the trimetallic NiCo2−xFexO4 nanoboxes with superior electrocatalytic activity and stability toward oxygen evolution reaction.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A novel copper‐catalyzed carbonylative trifluoromethylation of unactivated alkenes has been developed. A broad range of β‐trifluoromethylated carboxylic acid derivatives were prepared in moderate to ...excellent yields from simple alkenes with excellent regioselectivity. It is noteworthy that ethylene gas, as the simplest olefin, can also be applied directly to obtain β‐trifluoromethylated amides and ester. This transformation presents the first example on carbonylative trifluoromethylation of alkenes.
A novel procedure on carbonylative trifluoromethylation of unactivated alkenes has been developed. Catalyzed by a copper catalyst, carbonylative difunctionalization of alkenes with Togni‐CF3 and nitrogen (or oxygen) nucleophiles occurred successfully. A variety of valuable β‐trifluoromethyl amides, esters and acids were obtained in good yields under mild conditions. Ethylene gas can also be successfully applied.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Non‐noble‐metal‐based nanomaterials can exhibit extraordinary electrocatalytic performance toward the oxygen evolution reaction (OER) by harnessing the structural evolution during catalysis and the ...synergistic effect between elements. However, the structure of active centers in bimetallic/multimetallic catalysts is under long‐time debate in the catalysis community. Here, an efficient bimetallic Ni–Fe selenide‐derived OER electrocatalyst is reported and the structure–activity correlation during the OER evolution studied. By combining experiments and theoretical calculations, a conceptual advance is provided, in that the local coordination structure distortion and disordering of active sites inherited from the pre‐catalyst and post‐formed by a further reconstruction are responsible for boosting the OER performance. The active center is identified on Ni sites showing moderate bindings with oxygenous intermediates rather than Fe sites with strong and poisonous adsorptions. These findings provide crucial understanding in manipulating the local coordination and electronic structures toward rational design and fabrication of efficient OER electrocatalysts.
Bimetallic Ni–Fe selenide‐derived (oxy)hydroxide nanocage electrocatalysts are in situ generated by inheriting the structure of the pre‐catalyst. The successful manipulation of the local coordination and electronic structures of the electrocatalyst enables superior electrocatalytic activity and stability for the oxygen evolution reaction.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Alloying noble metals with non-noble metals enables high activity while reducing the cost of electrocatalysts in fuel cells. However, under fuel cell operating conditions, state-of-the-art oxygen ...reduction reaction alloy catalysts either feature high atomic percentages of noble metals (>70%) with limited durability or show poor durability when lower percentages of noble metals (<50%) are used. Here, we demonstrate a highly-durable alloy catalyst derived by alloying PtPd (<50%) with 3d-transition metals (Cu, Ni or Co) in ternary compositions. The origin of the high durability is probed by in-situ/operando high-energy synchrotron X-ray diffraction coupled with pair distribution function analysis of atomic phase structures and strains, revealing an important role of realloying in the compressively-strained single-phase alloy state despite the occurrence of dealloying. The implication of the finding, a striking departure from previous perceptions of phase-segregated noble metal skin or complete dealloying of non-noble metals, is the fulfilling of the promise of alloy catalysts for mass commercialization of fuel cells.
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