Designing efficient electrocatalysts for hydrogen evolution reaction is significant for renewable and sustainable energy conversion. Here, we report single-atom platinum decorated nanoporous Co
Se ...(Pt/np-Co
Se) as efficient electrocatalysts for hydrogen evolution. The achieved Pt/np-Co
Se shows high catalytic performance with a near-zero onset overpotential, a low Tafel slope of 35 mV dec
, and a high turnover frequency of 3.93 s
at -100 mV in neutral media, outperforming commercial Pt/C catalyst and other reported transition-metal-based compounds. Operando X-ray absorption spectroscopy studies combined with density functional theory calculations indicate that single-atom platinum in Pt/np-Co
Se not only can optimize surface states of Co
Se active centers under realistic working conditions, but also can significantly reduce energy barriers of water dissociation and improve adsorption/desorption behavior of hydrogen, which synergistically promote thermodynamics and kinetics. This work opens up further opportunities for local electronic structures tuning of electrocatalysts to effectively manipulate its catalytic properties by an atomic-level engineering strategy.
The real capacity of graphene and the lithium-storage process in graphite are two currently perplexing problems in the field of lithium ion batteries. Here we demonstrate a three-dimensional bilayer ...graphene foam with few defects and a predominant Bernal stacking configuration, and systematically investigate its lithium-storage capacity, process, kinetics, and resistances. We clarify that lithium atoms can be stored only in the graphene interlayer and propose the first ever planar lithium-intercalation model for graphenic carbons. Corroborated by theoretical calculations, various physiochemical characterizations of the staged lithium bilayer graphene products further reveal the regular lithium-intercalation phenomena and thus fully illustrate this elementary lithium storage pattern of two-dimension. These findings not only make the commercial graphite the first electrode with clear lithium-storage process, but also guide the development of graphene materials in lithium ion batteries.
The presence of rich polymorphs and stacking polytypes in molybdenum disulfide (MoS2) endows it with a diverse range of electrical, catalytic, optical, and magnetic properties. This has stimulated a ...lot of interest in the unique properties associated with each polymorph. Most techniques used for polymorph identification in MoS2 are macroscopic techniques that sample averaged properties due to their limited spatial resolution. A reliable way of differentiating the atomic structure of different polymorphs is needed in order to understand their growth dynamics and establish the correlation between structure and properties. Herein, the use of electron microscopy for identifying the atomic structures of several important polymorphs in MoS2, some of which are the subjects of mistaken assignment in the literature, is discussed. In particular, scanning transmission electron microscopy‐annular dark field imaging has emerged as the most effective and reliable approach for identifying the different phases in MoS2 and other 2D materials because its images can be directly correlated to the atomic structures. Examples of the identification of polymorphs grown under different conditions in molecular beam epitaxy or chemical vapor deposition, for example, 3R, 1T, 1T′‐phases, and 1T′‐edges, are presented, including their atomic structures, fascinating properties, growth methods, and corresponding thermodynamic stabilities.
The presence of rich polymorphs and stacking polytypes in molybdenum disulfide (MoS2) endows it with a diverse range of properties. This has stimulated great interest in the unique properties associated with each polymorph. The use of electron microscopy for identifying the atomic structures of several important polymorphs in MoS2 is discussed and the correlation between structure and properties is established.
The electrocatalytic nitrogen reduction reaction (NRR) provides a promising strategy to convert the abundant but inert N2 into NH3 using renewable energy. Herein, single‐atom Au isolated onto ...bicontinous nanoporous MoSe2 (np‐MoSe2) is designed as an electrocatalyst for achieving highly efficient NRR catalysis, which exhibits a high Faradaic efficiency (FE) of 37.82% and an NH3 production rate of 30.83 µg h−1 mg−1 at –0.3 V versus a reversible hydrogen electrode (RHE) in 0.1 m Na2SO4 under ambient conditions. Experimental and theoretical investigations reveal that the introduction of single Au atoms onto np‐MoSe2 optimizes the adsorption of NRR intermediates while suppressing the competing HER, thus providing an energetic‐favorable process for enhancing the catalytic selectivity toward electrochemical N2 reduction into NH3.
Single Au atoms/clusters isolated onto nanoporous MoSe2 catalyst is constructed by the combination of chemical vapor deposition (CVD) process and chemical etching. The resulting catalyst is highly active and stable toward electrochemical nitrogen reduction with a much higher ammonia yield (30.83 µg h−1 mg−1) and Faradaic efficiency (FE, 37.82%) than well‐studied Mo‐based catalysts. This work not only paves a favorable avenue for exploring and designing single‐atoms anchored onto 2D materials, but also provides insights into regulating the reaction pathway for the nitrogen reduction reaction (NRR).
Although 2D layered metal compounds are widely exploited using various techniques such as exfoliation and vapor‐phase‐assisted growth, it is still challenging to construct the 2D materials in a 3D ...configuration with preservation of the unique physicochemical properties of the metal compounds. Herein, a general synthetic strategy is reported for a wide variety of 2D (atomic‐scale thickness) metal compounds with 3D bicontinous nanoporous structure. 19 binary compounds including sulfides, selenides, tellurides, carbides, and nitrides, and five alloyed compounds, are successfully prepared via a surface alloy strategy, which are readily created by using a recyclable nanoporous gold assisted chemical vapor deposition process. These 3D nanoporous metal compounds with preserved 2D physicochemical properties, tunable pore sizes, and compositions for electrocatalytic applications, show excellent catalytic performance in the electrochemical N2 reduction reaction. This work opens up a promising avenue for fundamental studies and potential applications of a wide variety of nanoporous metal compounds.
2D metal compounds with bicontinous nanoporous structure are successfully prepared by using a recyclable nanoporous gold assisted chemical vapor deposition process. The resulting 3D nanoporous MoSSe with tunable pore sizes and porosity exhibits excellent electrochemical N2 reduction reaction properties. This work opens up a promising avenue for fundamental studies and potential applications of a wide variety of nanoporous metal compounds.
3D dealloyed nanoporous metals have emerged as a new class of catalysts for various chemical and electrochemical reactions. Similar to other heterogeneous catalysts, the surface atomic structure of ...the nanoporous metal catalysts plays a crucial role in catalytic activity and selectivity. Through surfactant‐assisted bottom‐up synthesis, the surface‐structure modification has been successfully realized in low‐dimensional particulate catalysts. However, the surface modification by top‐down dealloying has not been well explored for nanoporous metal catalysts. Here, a surfactant‐free approach to tailor the surface structure of nanoporous gold by surface relaxation via electrochemical redox cycling is reported. By controlling the scan rates, nanoporous gold with abundant {111} facets or {100} facets can be designed and fabricated with dramatically improved electrocatalysis toward the ethanol oxidation reaction.
A surfactant‐free potential‐cycling approach is developed to tailor the surface structure of 3D nanoporous gold with an abundance of {111} or {100} facets by controlling the scan rates. The {111}‐rich sample exhibits dramatically improved electrocatalysis toward the ethanol oxidation reaction in comparison with as‐dealloyed conventional nanoporous gold.
Traditional strategies for improving piezoelectric properties have focused on phase boundary engineering through complex chemical alloying and phase control. Although they have been successfully ...employed in bulk materials, they have not been effective in thin films due to the severe deterioration in epitaxy, which is critical to film properties. Contending with the opposing effects of alloying and epitaxy in thin films has been a long-standing issue. Herein we demonstrate a new strategy in alkali niobate epitaxial films, utilizing alkali vacancies without alloying to form nanopillars enclosed with out-of-phase boundaries that can give rise to a giant electromechanical response. Both atomically resolved polarization mapping and phase field simulations show that the boundaries are strained and charged, manifesting as head-head and tail-tail polarization bound charges. Such charged boundaries produce a giant local depolarization field, which facilitates a steady polarization rotation between the matrix and nanopillars. The local elastic strain and charge manipulation at out-of-phase boundaries, demonstrated here, can be used as an effective pathway to obtain large electromechanical response with good temperature stability in similar perovskite oxides.
Tuning surface structures by bottom-up synthesis has been demonstrated as an effective strategy to improve the catalytic performances of nanoparticle catalysts. Nevertheless, the surface modification ...of three-dimensional nanoporous metals, fabricated by a top-down dealloying approach, has not been achieved despite great efforts devoted to improving the catalytic performance of three-dimensional nanoporous catalysts. Here we report a surfactant-modified dealloying method to tailor the surface structure of nanoporous gold for amplified electrocatalysis toward methanol oxidation and oxygen reduction reactions. With the assistance of surfactants, {111} or {100} faceted internal surfaces of nanoporous gold can be realized in a controllable manner by optimizing dealloying conditions. The surface modified nanoporous gold exhibits significantly enhanced electrocatalytic activities in comparison with conventional nanoporous gold. This study paves the way to develop high-performance three-dimensional nanoporous catalysts with a tunable surface structure by top-down dealloying for efficient chemical and electrochemical reactions.
The presence of rich polymorphs and stacking polytypes in molybdenum disulfide (MoS2) endows it with a diverse range of properties. This has stimulated a lot of interest in the unique properties ...associated with each polymorph. In article number 1802397, Kian Ping Loh and co‐workers discuss the use of electron microscopy for identifying the atomic structures of several important polymorphs in MoS2 and establishing the correlation between structure and properties.
Scanning distortion correction in STEM images Ning, Shoucong; Fujita, Takeshi; Nie, Anmin ...
Ultramicroscopy,
January 2018, 2018-01-00, 20180101, Letnik:
184, Številka:
Pt A
Journal Article
Recenzirano
•Via theoretical modeling and simulation, a deep understanding of the noise influence on the real and reciprocal spaces of STEM images is achieved.•The atom positions are paid attention in our ...generalized scanning noise correction method based on a perpendicular scanned STEM image pair.•Our method takes all ranges of scanning noise frequency into account, and ensures real time correction.•Scanning noise induced deviations are corrected and the signal to noise ratio is significantly increased in STEM images.
Various disturbances do exist in the image taking process of scanning transmission electron microscopes (STEM), which seriously reduces the resolution and accuracy of STEM images. In this paper, a deep understanding of the scanning distortion influence on the real and reciprocal spaces of STEM images is achieved via theoretical modeling and simulation. A scanning distortion correction algorithm is further developed based on two images scanned along perpendicular directions, which is able to effectively correct scanning distortion induced deviations and significantly increase the signal to noise ratio of STEM images.
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