Because H2 is considered a promising clean energy source, water electrolysis has attracted great interest in related research and technology. Noble‐metal‐based catalysts are used as electrode ...materials in water electrolyzers, but their high cost and low abundance have impeded them from being used in practical areas. Recently, metal sulfides and phosphides based on earth‐abundant transition metals have emerged as promising candidates for efficient water‐splitting catalysts. Most studies have focused on adjusting the composition of the metal sulfides and phosphides to enhance the catalytic performance. However, morphology control of catalysts, including faceted and hollow structures, is much less explored for these systems because of difficulties in the synthesis, which requires a deep understanding of the nanocrystal growth process. Herein, representative synthetic methods for morphology‐controlled metal sulfides and phosphides are introduced to provide insights into these methodologies. The electrolytic performance of morphology‐controlled metal sulfide‐ and phosphide‐based nanocatalysts with enhanced surface area and intrinsically high catalytic activity is also summarized and the future research directions for this promising catalyst group is discussed.
Metal sulfide and phosphide nanoparticles have emerged as viable alternatives to expensive noble‐metal‐based electrocatalysts for water splitting. The recent significant developments of morphology‐controlled metal sulfide and phosphide nanoparticles as electrcatalysts for the hydrogen evolution reaction and oxygen evolution reaction are addressed.
Thermoelectrics, which can generate electricity from a temperature difference, or vice versa, is a key technology for solid‐state cooling and energy harvesting; however, its applications are ...constrained owing to low efficiency. Since the conversion efficiency of thermoelectric devices is directly obtained via a figure of merit of materials, zT, which is related to the electronic and thermal transport characteristics, the aim here is to elucidate physical parameters that should be considered to understand transport phenomena in semiconducting materials. It is found that the weighted mobility ratio of the majority and minority carrier bands is an important parameter that determines zT. For nanograined Bi–Sb–Te alloy, the unremarked role of this parameter on temperature‐dependent electronic transport properties is demonstrated. This analysis shows that the control of the weighted mobility ratio is a promising way to enhance zT of narrow bandgap thermoelectric materials.
Suppression of the bipolar conduction in narrow‐bandgap thermoelectric materials is crucial for improving their device efficiency. This work correlates the weighted mobility ratio in thermoelectric figure of merit and bipolar conduction in bismuth‐telluride‐based alloys. The results suggest that increasing the weighted mobility ratio suppresses the bipolar conduction most effectively among other parameters like carrier concentration and bandgap.
A synthesis strategy for the preparation of ultrathin free‐standing ternary‐alloy nanosheets is reported. Ultrathin Pd‐Pt‐Ag nanosheets with a thickness of approximately 3 nm were successfully ...prepared by co‐reduction of the metal precursors in an appropriate molar ratio in the presence of CO. Both the presence of CO and the interplay between the constituent metals provide fine control over the anisotropic two‐dimensional growth of the ternary‐alloy nanostructure. The prepared Pd‐Pt‐Ag nanosheets were superior catalysts of ethanol electrooxidation owing to their specific structural and compositional characteristics. This approach will pave the way for the design of multicomponent 2D nanomaterials with unprecedented functions.
Ultrathin Pd‐Pt‐Ag nanosheets with a thickness of approximately 3 nm were successfully prepared by the co‐reduction of suitable metal precursors in an appropriate molar ratio in the presence of CO. These nanosheets are superior catalysts of ethanol electrooxidation owing to their specific structural and compositional characteristics.
Atomically ordered intermetallic nanoparticles exhibit improved catalytic activity and durability relative to random alloy counterparts. However, conventional methods with time‐consuming and ...high‐temperature syntheses only have rudimentary capability in controlling the structure of intermetallic nanoparticles, hindering advances of intermetallic nanocatalysts. We report a template‐directed strategy for rapid synthesis of Pd‐based (PdM, M=Pb, Sn and Cd) ultrathin porous intermetallic nanosheets (UPINs) with tunable sizes. This strategy uses preformed seeds, which act as the template to control the deposition of foreign atoms and the subsequent interatomic diffusion. Using the oxygen reduction reaction (ORR) as a model reaction, the as‐synthesized Pd3Pb UPINs exhibit superior activity, durability, and methanol tolerance. The favored geometrical structure and interatomic interaction between Pd and Pb in Pd3Pb UPINs are concluded to account for the enhanced ORR performance.
This template‐directed synthetic strategy is a universal route for shape‐controlled synthesis of intermetallic nanocrystals and will provide new opportunities for intermetallic nanocatalysts.
Band engineering is an effective strategy to improve the electronic transport properties of semiconductors. In thermoelectric materials research, density‐of‐states effective mass is an undoubted key ...factor in verifying the band engineering effect and establishing a strategy for enhancing thermoelectric performance. However, estimation of the effective mass is demanding or inaccurate depending on the methods taken. A simple equation is proposed, valid for all degeneracy: Log10 (md*T/300) = (2/3) Log10 (n) − (2/3) 20.3 − (0.00508 × |S|) + (1.58 × 0.967|S|) that utilizes experimentally determined Seebeck coefficient (S) and carrier concentration (n) to determine the effective mass (md*) at a temperature (T). This straightforward equation, which gives an accurate analysis of the band modulation in terms of md*, is indispensable in designing thermoelectric materials of maximized performance.
The density‐of‐states (DOS) effective mass of thermoelectric materials can be estimated accurately with the single parabolic band model. However due to complex Fermi integral calculations involved, an equation that is valid in degenerate materials is instead utilized erroneously. This work proposes another simple, universal, and accurate equation that can be used for any degeneracy to determine the DOS effective mass.
The harsh operating conditions of the oxygen evolution reaction (OER) in water electrolysis severely degrade the activity and stability of the electrocatalysts due to elemental leaching or particle ...agglomeration. Therefore, it is crucial to incorporate support materials that effectively immobilize catalyst particles for developing efficient OER catalysts. This review aims to highlight the role of MXene as a support material to improve the performance of OER catalysts. First, the extended OER mechanism is briefly described in terms of the effect of MXene support on OER catalysts. Then, various synthesis methods of MXene and catalyst‐MXene compounds are introduced, and important properties of MXene that are beneficial to improve OER performances are discussed. The electrocatalytic results of the enhanced OER catalysts due to the effective MXene support are also summarized. Finally, future challenges and prospects are proposed for utilizing MXene as an excellent support material for various electrocatalysis.
This article reviews the properties of MXene as a support material for enhancing oxygen evolution reaction (OER) performances. MXene enhances OER performance due to its ability to improve the conductivity, stability, and hydrophilicity of the catalyst. This review also highlights the advantages of MXene compared to other materials and provides future directions for utilizing MXene for various electrocatalysis.
Although metastable crystal structures have received much attention owing to their utilization in various fields, their phase‐transition to a thermodynamic structure has attracted comparably little ...interest. In the case of nanoscale crystals, such an exothermic phase‐transition releases high energy within a confined surface area and reconstructs surface atomic arrangement in a short time. Thus, this high‐energy nanosurface may create novel crystal structures when some elements are supplied. In this work, the creation of a ruthenium carbide (RuCX, X < 1) phase on the surface of the Ru nanocrystal is discovered during phase‐transition from cubic‐close‐packed to hexagonal‐close‐packed structure. When the electrocatalytic hydrogen evolution reaction (HER) is tested in alkaline media, the RuCX exhibits a much lower overpotential and good stability relative to the counterpart Ru‐based catalysts and the state‐of‐the‐art Pt/C catalyst. Density functional theory calculations predict that the local heterogeneity of the outermost RuCX surface promotes the bifunctional HER mechanism by providing catalytic sites for both H adsorption and facile water dissociation.
Crystal phase‐transition of Ru/C from cubic‐close‐packing to hexagonal‐close‐packing creates a ruthenium carbide (RuCX, X < 1) nanosurface on Ru nanocrystal. The as‐created RuCX nanosurface presents a highly active and stable performance for the hydrogen evolution reaction (HER) in alkaline media. Density functional theory calculations predict the RuCX sites as bifunctional configurations for improving alkaline HER kinetics.
Perovskite solar cells (PSCs) exceeding a power conversion efficiency (PCE) of 20% have mainly been demonstrated by using mesoporous titanium dioxide (mp-TiO₂) as an electron-transporting layer. ...However, TiO₂ can reduce the stability of PSCs under illumination (including ultraviolet light). Lanthanum (La)–doped BaSnO₃ (LBSO) perovskite would be an ideal replacement given its electron mobility and electronic structure, but LBSO cannot be synthesized as well-dispersible fine particles or crystallized below 500°C. We report a superoxide colloidal solution route for preparing a LBSO electrode under very mild conditions (below 300°C).The PSCs fabricated with LBSO and methylammonium lead iodide (MAPbI₃) show a steady-state power conversion efficiency of 21.2%, versus 19.7% for a mp-TiO₂ device. The LBSO-based PSCs could retain 93% of their initial performance after 1000 hours of full-Sun illumination.
Background
Although recent advances in high-throughput technology have provided many insights into gastric cancer (GC), few reliable biomarkers for diffuse-type GC have been identified. Here, we aim ...to identify a prognostic and predictive signature of diffuse-type GC heterogeneity.
Methods
We analyzed RNA-seq-based transcriptome data to identify a molecular signature in 150 gastric tissue samples including 107 diffuse-type GCs. The predictive value of the signature was verified using other diffuse-type GC samples in three independent cohorts (
n
= 466). Log-rank and Cox regression analyses were used to estimate the association between the signature and prognosis. The signature was also characterized by somatic variant analyses and tissue microarray analysis between diffuse-type GC subtypes.
Results
Transcriptomic profiling of RNA-seq data identified a signature which revealed distinct subtypes of diffuse-type GC: the intestinal-like (INT) and core diffuse-type (COD) subtypes. The signature showed high predictability and independent clinical utility in diffuse-type GC prognosis in other patient cohorts (HR 2.058, 95% CI 1.53–2.77,
P
= 1.76 × 10
–6
). Integrative mutational and gene expression analyses demonstrated that the COD subtype was responsive to chemotherapy, whereas the INT subtype was responsive to immunotherapy with an immune checkpoint inhibitor (ICI). Tissue microarray analysis showed the practical utility of IGF1 and NXPE2 for predicting diffuse-type GC heterogeneity.
Conclusions
We present a molecular signature that can identify diffuse-type GC patients who display different clinical behaviors as well as responses to chemotherapy or ICI treatment.
Infectious complications are major causes of morbidity and mortality after liver transplantation,despite recent advances in the transplant field.Bacteria,fungi,viruses and parasites can cause ...infection before and after transplantation.Among them,bacterial infections are predominant during the first two months posttransplantation and affect patient and graft survival.They might cause surgical site infections,including deep intra-abdominal infections,bacteremia,pneumonia,catheter-related infections and urinary tract infections.The risk factors for bacterial infections differ between the periods after transplant,and between centers.Recently,the emergence of multi-drug resistant bacteria is great concern in liver transplant(LT)patients.The instructive data about effects of infections with extended-spectrum beta lactamase producing bacteria,carbapenem-resistant gram-negative bacteria,and glycopeptide-resistant gram-positive bacteria were reported on a center-by-center basis.To prevent posttransplant bacterial infections,proper strategies need to be established based upon center-specific data and evidence from well-controlled studies.This article reviewed the recent epidemiological data,risk factors for each type of infections and important clinical issues in bacterial infection after LT.
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