BIF-20, a zeolite-like porous boron imidazolate framework with high density of exposed B-H bonding, is combined with graphitic carbon nitride (g-CN) nanosheets via a facile electrostatic self-assembly approach under room temperature, forming an elegant composite BIF-20@g-CN nanosheet. The as-constructed composite preferably captures CO and further photoreduces CO in high efficiency. The photogenerated excitations from the carbon nitride nanosheet can directionally migrate to B-H bonding, which effectively suppresses electron-hole pair recombination and thus greatly improves the photocatalytic ability. Compared to the g-CN nanosheet, the BIF-20@g-CN nanosheet composite displayed a much-enhanced photocatalytic CO reduction activity, which is equal to 9.7-fold enhancements in the CH evolution rate (15.524 μmol g h) and 9.85-fold improvements in CO generation rate (53.869 μmol g h). Density functional theory simulations further prove that the presence of B-H bonding in the composite is favorable for CO adhesion and activation in the reaction process. Thus, we believe that the implantation of functional active sites into the porous matrix provides important insights for preparation of a highly efficient photocatalyst.
Achieving a molecular level understanding of surface performance of nanomaterials by modulating the electronic structure is important but challenging. Here, we have developed a hollow microcube framework constructed by Mo-defect-rich ultrathin MoS2 nanosheets (HMF-MoS2) through a zeolite-like-framework-engaged strategy. The hollow structured HMF-MoS2 delivers an impressive specific capacity (384.3 mA h g–1 after 100 cycles at 100 mA g–1) and cycle stability (267 mA h g–1 after 125 cycles at 1 A g–1) for sodium storage. As evidenced by experiments and density functional theory calculations, abundant Mo vacancies in MoS2 can greatly accelerate the charge transfer and enhance the interaction between MoS2 and sodium, resulting in the promotion of sodium storage. Kinetic analysis result reveals that the ultrafast sodium ion storage of HMF-MoS2 could be associated with the significant contribution of capacitive energy storage. This work highlights the detailed molecular level understanding of chemical reaction on MoS2 surface by defect and morphology engineering, which can be applied to other metal sulfides for energy storage devices.
Reducing the dimensions of metallic nanoparticles to isolated, single atom has attracted considerable attention in heterogeneous catalysis, because it significantly improves atomic utilization and often leads to distinct catalytic performance. Through extensive research, it has been recognized that the local coordination environment of single atoms has an important influence on their electronic structures and catalytic behaviors. In this review, we summarize a series of representative systems of single-atom catalysts, discussing their preparation, characterization, and structure–property relationship, with an emphasis on the correlation between the coordination spheres of isolated reactive centers and their intrinsic catalytic activities. We also share our perspectives on the current challenges and future research promises in the development of single-atom catalysis. With this article, we aim to highlight the possibility of finely tuning the catalytic performances by engineering the coordination spheres of single-atom sites and provide new insights into the further development for this emerging research field.
Transition metal dichalcogenides (TMDCs) hold great promise for electrochemical energy conversion technologies in view of their unique structural features associated with the layered structure and ultrathin thickness. Because the inert basal plane accounts for the majority of a TMDC's bulk, activation of the basal plane sites is necessary to fully exploit the intrinsic potential of TMDCs. Here, recent advances on TMDCs‐based hybrids/composites with greatly enhanced electrochemical activity are reviewed. After a summary of the synthesis of TMDCs with different sizes and morphologies, comprehensive in‐plane activation strategies are described in detail, mainly including in‐plane‐modification‐induced phase transformation, surface‐layer modulation, and interlayer modification/coupling. Simultaneously, the underlying mechanisms for improved electrochemical activities are highlighted. Finally, the strategic evaluation on further research directions of TMDCs in‐plane activation is featured. This work would shed some light on future design trends of TMDCs‐based functional materials for electrochemical energy‐related applications.
Perturbing the periodic electronic structure of the MoS2 basal plane via vacancy engineering offers an opportunity to explore its intrinsic activity. A significant challenge is the design of vacancy states, which include its type, distribution, and accessibility. Here, well-dispersed and vertically aligned MoS2 nanosheets with an in-plane selectively cleaved Mo–S bond on a carbon matrix (c-MoS2–C) have been prepared by a self-engaged strategy, which synergistically realizes uniform vacancy manufacturing and three-dimensional (3D) self-assembly of the defective MoS2 nanosheets. X-ray adsorption spectroscopy investigation confirms that the cleaved MoS2 basal plane generates newly active edge sites, where the Mo centers feature unsaturated coordination geometry. Theoretical calculations reveal that the exposed interior edge Mo sites represent new active centers for hydrogen adsorption/desorption. As expected, the synthesized c-MoS2–C exhibits markedly enhanced hydrogen evolution activity and superior stability. This in-plane activation strategy could be extended to other types of transition-metal dichalcogenides and catalytic reaction systems.
Nanoparticles comprising three or more different metals are challenging to prepare. General methods that tackle this challenge are highly sought after as multicomponent metal nanoparticles display favorable properties in applications such as catalysis, biomedicine, and imaging. Herein, we report a practical and versatile approach for the synthesis of nanoparticles composed of up to four different metals. This method relies on the thermal decomposition of nanostructured composite materials assembled from platinum nanoparticles, a metal-organic framework (ZIF-8), and a tannic acid coordination polymer. The controlled integration of multiple metal cations (Ni, Co, Cu, Mn, Fe, and/or Tb) into the tannic acid shell of the precursor material dictates the composition of the final multicomponent metal nanoparticles. Upon thermolysis, the platinum nanoparticles seed the growth of the multicomponent metal nanoparticles via coalescence with the metallic constituents of the tannic acid coordination polymer. The nanoparticles are supported in the walls of hollow nitrogen-doped porous carbon capsules created by the decomposition of the organic components of the precursor. The capsules prevent sintering and detachment of the nanoparticles, and their porosity allows for efficient mass transport. To demonstrate the utility of producing a broad library of supported multicomponent metal nanoparticles, we tested their electrocatalytic performance toward the hydrogen evolution reaction and oxygen evolution reaction. We discovered functional relationships between the composition of the nanoparticles and their electrochemical activity and identified the PtNiCu and PtNiCuFe nanoparticles as particularly efficient catalysts. This highlights how to generate diverse libraries of multicomponent metal nanoparticles that can be synthesized and subsequently screened to identify high-performance materials for target applications.
Interface engineering is a promising strategy for boosting the catalytic performances via the optimized coordination. Herein, we developed a top-down strategy to in situ obtain the nanocomposite of N, S-decorated porous carbon matrix encapsulated WS2/W2C (WS2/W2C@NSPC). The as-synthesized hybrid is characterized by excellent interface coupling in atomic level, good electrical conductivity, and high active surface area. Electrochemical measurements show that the optimized catalyst exhibits remarkable electrocatalytic activity for hydrogen evolution in both acidic and alkaline media. These results should be attributed to the abundant active sites existing in the different phase boundaries, resulting from a synergistic effect of the activated WS2/W2C heterostructure and the highly conductive carbon matrix. This strategy opens new avenues toward understanding the relationship between chemical structure and catalytic performance in molecular level and thus providing a rational way to fabricate highly efficient and durable electrocatalysts.
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