Lead telluride has long been realized as an ideal p‐type thermoelectric material at an intermediate temperature range; however, its commercial applications are largely restricted by its n‐type ...counterpart that exhibits relatively inferior thermoelectric performance. This major limitation is largely solved here, where it is reported that a record‐high ZT value of ≈1.83 can be achieved at 773 K in n‐type PbTe‐4%InSb composites. This significant enhancement in thermoelectric performance is attributed to the incorporation of InSb into the PbTe matrix resulting in multiphase nanostructures that can simultaneously modulate the electrical and thermal transport. On one hand, the multiphase energy barriers between nanophases and matrix can boost the power factor in the entire temperature range via significant enhancement of the Seebeck coefficient and moderately reducing the carrier mobility. On the other hand, the strengthened interface scattering at the intensive phase boundaries yields an extremely low lattice thermal conductivity. This strategy of constructing multiphase nanostructures can also be highly applicable in enhancing the performance of other state‐of‐the‐art thermoelectric systems.
A new strategy of constructing multiphase nanostructures can enhance the thermoelectric power factor and reduce the lattice thermal conductivity simultaneously. Through this strategy, it is reported that a record‐high ZT value of ≈1.83 can be achieved at 773 K in n‐type PbTe‐4%InSb composites. Furthermore, the mechanisms introducing multiphase nanostructures are also highly applicable in other thermoelectric systems.
Herein, a series of porous nano‐structured carbocatalysts have been fused and decorated by Mo‐based composites, such as Mo2C, MoN, and MoP, to form a hybrid structures. Using the open porosity ...derived from the pyrolysis of metal–organic frameworks (MOFs), the highly dispersive MoO2 small nanoparticles can be deposited in porous carbon by chemical vapor deposition (CVD). Undergoing different treatments of carbonization, nitridation, and phosphorization, the Mo2C‐, MoN‐, and MoP‐decorated carbocatalysts can be selectively prepared with un‐changed morphology. Among these Mo‐based composites, the MoP@Porous carbon (MoP@PC) composites exhibited remarkable catalytic activity for the hydrogen evolution reaction (HER) in 0.5 m H2SO4 aqueous solution versus MoO2@PC, Mo2C@PC, and MoN@PC. This study gives a promising family of multifunctional lab‐on‐a‐particle architectures which shed light on energy conversion and fuel‐cell catalysis.
Decorated for HER: Using the open porosity derived from the pyrolysis of metal–organic frameworks (MOFs), MoO2 small nanoparticles can be deposited in the porous carbon by chemical vapor deposition. Carbonization, nitridation, or phosphorization, selectively gives Mo2C‐, MoN‐, and MoP‐decorated carbocatalysts with unchanged morphology. The catalysts are promising for the hydrogen evolution reaction.
Developing efficient and cost-effective electrocatalysts for hydrogen evolution reaction (HER) is highly desired for the hydrogen economy. In this study, we developed a facile microwave reduction ...method to synthesize single Pt atoms anchored on aniline-stacked graphene (Pt SASs/AG) with outstanding HER performance. Pt SASs/AG presents excellent HER activity with η = 12 mV at 10 mA cm −2 and a mass current density of 22 400 Ag Pt −1 at η = 50 mV, which is 46 times higher than that of commercial 20 wt% Pt/C. Moreover, the Pt SASs/AG catalyst is highly active and more stable than Pt/C. X-ray absorption fine spectroscopy and density functional theory calculations demonstrated that the coordination of atomically isolated Pt with the nitrogen of aniline optimized the electronic structure of Pt and the hydrogen adsorption energy, eventually promoting HER activity. This study provides a new avenue for the development of single-atom Pt electrocatalysts with high activity and stability.
Strain engineering has been a powerful strategy to finely tune the catalytic properties of materials. We report a tensile-strained two-to-three atomic-layer Pt on intermetallic Pt3Ga (AL-Pt/Pt3Ga) as ...an active electrocatalyst for the methanol oxidation reaction (MOR). Atomic-resolution high-angle annular dark-field scanning transmission electron microscopy characterization showed that the AL-Pt possessed a 3.2% tensile strain along the 001 direction while having a negligible strain along the 100/010 direction. For MOR, this tensile-strained AL-Pt electrocatalyst showed obviously higher specific activity (7.195 mA cm–2) and mass activity (1.094 mA/μgPt) than those of its unstrained counterpart and commercial Pt/C catalysts. Density functional theory calculations demonstrated that the tensile-strained surface was more energetically favorable for MOR than the unstrained one, and the stronger binding of OH* on stretched AL-Pt enabled the easier removal of CO*.
Designing highly active and robust platinum-free catalysts for hydrogen evolution reaction is of vital importance for clean energy applications yet challenging. Here we report highly active and ...stable cobalt-substituted ruthenium nanosheets for hydrogen evolution, in which cobalt atoms are isolated in ruthenium lattice as revealed by aberration-corrected high-resolution transmission electron microscopy and X-ray absorption fine structure measurement. Impressively, the cobalt-substituted ruthenium nanosheets only need an extremely low overpotential of 13 mV to achieve a current density of 10 mA cm
in 1 M KOH media and an ultralow Tafel slope of 29 mV dec
, which exhibit top-level catalytic activity among all reported platinum-free electrocatalysts. The theoretical calculations reveal that the energy barrier of water dissociation can greatly reduce after single cobalt atom substitution, leading to its superior hydrogen evolution performance. This study provides a new insight into the development of highly efficient platinum-free hydrogen evolution catalysts.
Improving the catalytic selectivity of Pd catalysts is of key importance for various industrial processes and remains a challenge so far. Given the unique properties of single-atom catalysts, ...isolating contiguous Pd atoms into a single-Pd site with another metal to form intermetallic structures is an effective way to endow Pd with high catalytic selectivity and to stabilize the single site with the intermetallic structures. Based on density functional theory modeling, we demonstrate that the (110) surface of Pm3̅m PdIn with single-atom Pd sites shows high selectivity for semihydrogenation of acetylene, whereas the (111) surface of P4/mmm Pd3In with Pd trimer sites shows low selectivity. This idea has been further validated by experimental results that intermetallic PdIn nanocrystals mainly exposing the (110) surface exhibit much higher selectivity for acetylene hydrogenation than Pd3In nanocrystals mainly exposing the (111) surface (92% vs 21% ethylene selectivity at 90 °C). This work provides insight for rational design of bimetallic metal catalysts with specific catalytic properties.
Here we report a precise control of isolated single ruthenium site supported on nitrogen-doped porous carbon (Ru SAs/N–C) through a coordination-assisted strategy. This synthesis is based on the ...utilization of strong coordination between Ru3+ and the free amine groups (−NH2) at the skeleton of a metal–organic framework, which plays a critical role to access the atomically isolated dispersion of Ru sites. Without the assistance of the amino groups, the Ru precursor is prone to aggregation during the pyrolysis process, resulting in the formation of Ru clusters. The atomic dispersion of Ru on N-doped carbon can be verified by the spherical aberration correction electron microscopy and X-ray absorption fine structure measurements. Most importantly, this single Ru sites with single-mind N coordination can serve as a semihomogeneous catalyst to catalyze effectively chemoselective hydrogenation of functionalized quinolones.
For successful gene therapy, the delivery of the curative genetic information into target cells is the main hurdle and the development of efficient and safe gene delivery carriers the crucial ...challenge. Polymeric materials have been widely investigated as gene delivery agents, generating first promising results. However, the heterogeneity and polydispersity of polymers and lack of site specific modifications make it difficult to achieve accurate structure‐activity relationship studies. Moreover it will hamper manufacturing of highly defined materials which could be used in clinical development. Therefore, polymers with precise chemical structure are required. In this review, we focus on the current design of defined polymeric materials for gene transfer. We first discuss the barriers for gene delivery, and then provide examples which illustrate defined polymeric vectors, including dendrimers, peptide carriers, and sequence‐defined oligoaminoamides.
Polymers with precise chemical structure will be useful gene delivery carriers. Due to the different extracellular and intracellular delivery barriers, multiple transport functions have to be incorporated in a site‐specific manner into precise molecular backbones. Strategies for the design of such defined carrier materials, including dendrimers, peptides, and sequence‐defined oligoaminoamides are reviewed.
The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic ...structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum-nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum-nickel catalyst, and this composite catalyst composed of crystalline platinum-nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon.
Phosphate ore is an important raw material for manufacturing fertilizers and phosphorous chemical products. While most of the phosphate resources cannot be directly treated as feed stock due to the ...low grade of P2O5 and high content of impurities. In order to obtain a qualified phosphate concentrate, the beneficiation of the low-grade phosphate ore is, hence, of great necessity. Many beneficiation techniques can be employed to upgrade the P2O5 grade of phosphate ores based on their characteristics in chemical composition and texture. The flotation process is most widely applied to balance the P2O5 recovery ratio and cost. In this review, the dominant techniques for the beneficiation of phosphate ores are introduced. Moreover, the factors that affect the flotation of phosphate ore, including the properties of mineralogy, flotation reagents (depressants and collectors) and flotation medium, were systematically analyzed.
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