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The photofixation and utilization of CO 2 via single-electron mechanism is considered to be a clean and green way to produce high-value-added commodity chemicals with long carbon chains. However, this topic has not been fully explored for the highly negative reduction potential in the formation of reactive carbonate radical. Herein, by taking Bi 2 O 3 nanosheets as a model system, we illustrate that oxygen vacancies confined in atomic layers can lower the adsorption energy of CO 2 on the reactive sites, and thus activate CO 2 by single-electron transfer in mild conditions. As demonstrated, Bi 2 O 3 nanosheets with rich oxygen vacancies show enhanced generation of •CO 2 – species during the reaction process and achieve a high conversion yield of dimethyl carbonate (DMC) with nearly 100% selectivity in the presence of methanol. This study establishes a practical way for the photofixation of CO 2 to long-chain chemicals via defect engineering. The photofixation and utilization of CO 2 is considered to be a clean and green way to produce high-value-added commodity chemicals, but production of long chain chemicals through this process remains a challenge. Here, the authors develop a practical way for the photofixation of CO 2 to long-chain chemicals via defect engineering.

Ultrathin metal layers can be highly active carbon dioxide electroreduction catalysts, but may also be prone to oxidation. Here we construct a model of graphene confined ultrathin layers of highly reactive metals, taking the synthetic highly reactive tin quantum sheets confined in graphene as an example. The higher electrochemical active area ensures 9 times larger carbon dioxide adsorption capacity relative to bulk tin, while the highly-conductive graphene favours rate-determining electron transfer from carbon dioxide to its radical anion. The lowered tin–tin coordination numbers, revealed by X-ray absorption fine structure spectroscopy, enable tin quantum sheets confined in graphene to efficiently stabilize the carbon dioxide radical anion, verified by 0.13 volts lowered potential of hydroxyl ion adsorption compared with bulk tin. Hence, the tin quantum sheets confined in graphene show enhanced electrocatalytic activity and stability. This work may provide a promising lead for designing efficient and robust catalysts for electrolytic fuel synthesis. Ultrathin metal layers can be highly active carbon dioxide electroreduction catalysts but may also be prone to oxidation. Here, the authors report the fabrication of reactive tin quantum nanosheets confined in graphene and demonstrate their enhanced electrocatalytic activity and stability.

Ultrathin nanosheets are considered as one kind of the most promising candidates for the fabrication of flexible electrochromic devices (ECDs) due to their permeable channels, high specific surface areas and good contact with the substrate. Herein, we first report the synthesis of large-area nanosheets of tungsten oxide dihydrate (WO 3 ·2H 2 O) with a thickness of only about 1.4 nm, showing much higher Li + diffusion coefficients than those of the bulk counterpart. The WO 3 ·2H 2 O ultrathin nanosheets are successfully assembled into the electrode of flexible electrochromic device, which exhibits wide optical modulation, fast color-switching speed, high coloration efficiency, good cyclic stability and excellent flexibility. Moreover, the electrochromic mechanism of WO 3 ·2H 2 O is further investigated by first-principle density functional theory (DFT) calculations, in which the relationship between structural features of ultrathin nanosheets and coloration/bleaching response speed is revealed.

In tokamak, tungsten nitrides (WN x ) layers that form on the divertor surface are byproducts of the nitrogen seeding system. The impact of their thermal transport properties is an important issue as they will be subjected to continuous high heat flow during operation. Leveraging density functional theory calculations along with the Kubo-Greenwood method, we investigate how vacancy defects influence the electrical conductivity and thermal conductivity of h-W 2 N 1 , β-W 1 N 1 , and h-W 2 N 3 compounds, respectively. Our findings suggest that both nitrogen vacancy and tungsten vacancy defects can suppress the electrical and thermal conductivities of β-W 1 N 1 to some extent. The electrical and thermal conductivity of h-W 2 N 1 compound decrease in the presence of W vacancy but are insensitive to N vacancy. Conversely, for h-W 2 N 3 , both types of vacancy defects can enhance its electrical and thermal conductivities. Furthermore, we reveal that the fluctuation in the electrical conductivity of the three WN x compounds correlates with the changes in the mean free path of electrons and the density of states at the Fermi energy level induced by the vacancies in each system. The insights gleaned from our findings are beneficial for assessing and comprehending the thermal conductivity performance of WN x layers on the divertor surface. Understanding the thermal transport properties of tungsten nitrides formed on the divertor surface of the tokamak is crucial, as they will be subjected to continuous heat flux. In this article, the authors theoretically calculated the influence of vacancy defects on the electrical and thermal conductivities of tungsten nitrides, providing an understanding of the mechanism behind the effects in terms of electron behavior.

Quantum tunneling of magnetization (QTMs), stemming from their importance for understanding materials with unconventional properties, has continued to attract widespread theoretical and experimental attention. However, the observation of QTMs in the most promising candidates of molecular magnets and few iron-based compounds is limited to very low temperature. Herein, we first highlight a simple system, ultrasmall half-metallic V 3 O 4 quantum dots, as a promising candidate for the investigation of QTMs at high temperature. The quantum superparamagnetic state (QSP) as a high temperature signature of QTMs is observed at 16 K, which is beyond absolute zero temperature and much higher than that of conventional iron-based compounds due to the stronger spin-orbital coupling of V 3+ ions bringing high anisotropy energy. It is undoubtedly that this ultrasmall quantum dots, V 3 O 4 , offers not only a promising candidate for theoretical understanding of QTMs but also a very exciting possibility for computers using mesoscopic magnets.

Silicon is the most important semiconducting material in the microelectronics industry. If current miniaturization trends continue, minimum device features will soon approach the size of atomic clusters. In this size regime, the structure and properties of materials often differ dramatically from those of the bulk. An enormous effort has been devoted to determining the structures of free silicon clusters 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 . Although progress has been made for Si n with n < 8, theoretical predictions for larger clusters are contradictory 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 and none enjoy any compelling experimental support. Here we report geometries calculated for medium-sized silicon clusters using an unbiased global search with a genetic algorithm. Ion mobilities 23 determined for these geometries by trajectory calculations are in excellent agreement with the values that we measure experimentally. The cluster geometries that we obtain do not correspond to fragments of the bulk. For n = 12–18 they are built on a structural motif consisting of a stack of Si 9 tricapped trigonal prisms. For n ⩾ 19, our calculations predict that near-spherical cage structures become the most stable. The transition to these more spherical geometries occurs in the measured mobilities for slightly larger clusters than in the calculations, possibly because of entropic effects.

We present an orthogonal tight-binding (TB) potential model for W/Cu binary systems. This model can reasonably predict the electronic structures, elastic properties, and thermodynamics properties of W/Cu systems. Furthermore, by performing the TB Monte Carlo simulations and the TB molecular dynamics simulations, we find that (1) the W(110) surface in the fusion reactor exhibits pre-melting behaviors, (2) W and Cu atoms in a W/Cu binary system prefer to form single element domains, and (3) the interface between a W domain and a Cu domain degrades the transport property of the heat in a W/Cu system significantly.

An environment-dependent tight-binding potential model for copper within the framework of quantum theory is developed. Our benchmark calculations indicate that this model has good performance in describing the elastic property, the stability and the vibrational property of bulk copper, as well as in handling the clusters, the surfaces and the defective Cu systems. By combining this model with molecular dynamics, we study how the evolution of structural defects arising from the irradiation of the energetic particles influences the mechanical and the thermal properties of the copper-heat-sinks in fusion reactors. Based on our simulations, the heat blockade in the irradiated Cu-heat-sinks is predicted. This finding is valuable for the development of wall materials in fusion reactors.

Atomically dispersed metal has gained much attention because of the new opportunities they offer in catalysis. However, it is still crucial to understand the mechanism of single-atom catalysis at molecular level for expanding them to other more difficult catalytic reactions, such as ammonia synthesis from nitrogen. In fact, developing ammonia synthesis under ambient conditions to overcome the high energy consumption in well-established Haber-Bosch process has fascinated scientists for many years. Herein, we demonstrate that single Cu atom yields facile valence-electron isolation from the conjugated π electron cloud of p-CN. Electron spin resonance measurements reveal that these isolated valence electrons can be easily excited to generate free electrons under photo-illumination, thus inducing high efficient photo-induced ammonia synthesis under ambient conditions. The NH 3 producing rate of copper modified carbon nitride (Cu-CN) reached 186 μmol g −1 h −1 under visible light irradiation with the quantum efficiency achieved 1.01% at 420 nm monochromatic light. This finding surely offers a model to open up a new vista for the ammonia synthesis at gentle conditions. The introduction of single atom to isolate the valence electron also represents a new paradigm for many other photocatalytic reactions, since the most photoinduced processes have been successfully exploited sharing the same origin.

The photofixation and utilization of CO via single-electron mechanism is considered to be a clean and green way to produce high-value-added commodity chemicals with long carbon chains. However, this topic has not been fully explored for the highly negative reduction potential in the formation of reactive carbonate radical. Herein, by taking Bi O nanosheets as a model system, we illustrate that oxygen vacancies confined in atomic layers can lower the adsorption energy of CO on the reactive sites, and thus activate CO by single-electron transfer in mild conditions. As demonstrated, Bi O nanosheets with rich oxygen vacancies show enhanced generation of •CO species during the reaction process and achieve a high conversion yield of dimethyl carbonate (DMC) with nearly 100% selectivity in the presence of methanol. This study establishes a practical way for the photofixation of CO to long-chain chemicals via defect engineering.