Latest ArticlesHighly active and durable oxygen reduction reaction (ORR) catalysts with sufficient activity and stability of Pt are beneficial for the commercialization of proton exchange membrane fuel cells. Here we report an effective approach to prepare a composite catalyst comprising of ordered L12-Pt3Fe intermetallic nanoparticles interact with single atom Fe-Nx-Cy active sites. The addition of Fe and the confinement effect of hierarchical porous structure limit the growth of intermetallic particle size (around 2.5 nm). The ligand effect of the electron transfer from Fe to Pt and the synergistic interaction between L12-Pt3Fe and Fe-Nx-Cy work together to reduce oxygen intermediates adsorption and improve kinetics process. Experimentally, the L12-Pt3Fe/CFe-N-C catalyst shows high mass activity and specific activity at 1.010 A/mgPt and 1.166 mA/cm2, respectively, which are 5.8 and 5.1 times higher than those of commercial Pt/C (0.174 A/mgPt and 0.230 mA/cm2). Thanks to the more stable L12 structure, L12-Pt3Fe/CFe-N-C exhibits better durability (14 mV E1/2 loss of L12-Pt3Fe/CFe-N-C and 33 mV E1/2 loss of commercial Pt/C) after 30,000 cycles accelerated stress tests. The strategy to design and prepare small particle Pt-based intermetallic alloys coordinated with M-N-C active sites provides a new direction to obtain low-cost and easily prepared effective ORR catalysts.
Two-dimensional (2D) layered materials with layer-number dependent properties are promising candidates for next-generation noble-metal-free electrocatalytic reaction. However, the main group metal chalcogenides (MMCs) used for this purpose are rarely explored. Herein, we report the controlled growth of indium selenide (InSe) with a novel morphology (semispherical array) on a silicon substrate and its application in hydrogen evolution reaction (HER). The formation of the spherical InSe is explained with a vapor-liquid-solid growth mechanism, in which the distribution and size of the spheres could be facilely tuned by the reaction parameters. The InSe semispherical array was demonstrated as more efficient catalyst for HER than the flake-like 2D InSe counterparts, originating from the fully exposed InSe spherical surface with abundant adsorbing sites and the high crystalline quality for electron transport. This work provides a controlled synthesis way of the layered InSe with a distinct spherical morphology used for the electrocatalysis applications and could be extended to other main group metal chalcogenides.
Defect engineering has been demonstrated to be an appealing strategy to boost the photocatalytic activity of materials. However, can higher defect concentration bring about higher photocatalytic activity? This is an open question. In this work, BiPO4 photocatalysts with controllable oxygen vacancy concentrations were successfully synthesized. The photocatalytic activity of the obtained BiPO4 photocatalysts was determined by the removal of ciprofloxacin and 4-chlorophenol, as well as CO2 photoreduction. The BiPO4 materials with lower oxygen vacancy concentration could display unexpected higher photocatalytic efficiency. Through the investigation of different factors which may affect the photocatalytic performance, such as crystal structure, morphology, specific surface area, defect, and energy band structure, it can be found that the energy band structure difference was responsible for the enhanced photocatalytic activity.
In order to balance the conductivity and flexural strength of graphite composite bipolar plates, the influence of conductive filler on the properties of graphite composite bipolar plate was comprehensively studied by using phenolic resin as binder, natural flake graphite as conductive substrate and functional carbon materials with different structures as auxiliary filler. The results show that the particle size of conductive substrate has an important influence on the conductivity enhancement of auxiliary filler. The influence of conductive particle size on auxiliary filler electrical conductivity improvement was first investigated in this research. The effects of various auxiliary filler concentrations on improving electrical conductivity and flexural strength were then examined. This research has substantial implications for the balance of electrical conductivity and flexural strength of graphite composite bipolar plates.
Understanding the influence of sulfates over catalysts for selective catalytic reduction of NO with NH3 (NH3-SCR) is crucial due to the universal presence of SO2 in exhaust gas. Depending on the degree of sulfation, there mainly exist surface and bulk sulfates and NH3-SCR activity is generally considered to suffer more from bulk sulfates. Herein, the unique function of bulk sulfates over CeO2 in promoting high-temperature SCR reaction is revealed. Notably, compared with CeO2 dominated with surface sulfates (S-CeO2–4h) and commercial V2O5-WO3/TiO2, CeO2 with bulk sulfates (S-CeO2–72h) exhibits admirable NO conversion at the temperature range of 400–550 ℃. Bulk sulfates provide more Brønsted acid sites with stronger strength for NH3 adsorption. Moreover, the oxidation ability of CeO2 is significantly inhibited due to electron-withdrawing effect from bulk sulfates, which alleviates NH3 oxidation at high temperatures. More NH3 adsorption with high stability and limited NH3 oxidation capacity ensure the excellent catalytic performance for S-CeO2–72h in high-temperature denitration. This work provides new insight of bulk sulfates in promoting SCR activity and open a new avenue to design deNOx catalysts employed at high temperatures.
Two erbium(Ⅲ) complexes [ErCl(OArAd)3][Na(THF)6] (1) and Er(OArAd)3 (2) are successfully prepared by using one variety of "hard" base ligand with large steric hindrance. The coordination geometry around the Er(Ⅲ) site changes from distorted tetrahedral to flat trigonal pyramid geometry in different solvent environment due to the removal of the coordinated chloride. Such an alternation significantly enhances the single-molecule magnet (SMM) behavior and makes the field-induced effective energy barrier (Ueff) arrive at 43(1) cm−1 for the latter. Together with theoretical calculations, this study shows that strong equatorial ligand field and high local symmetry are critical to suppress the quantum tunneling of the magnetization (QTM) and achieve high-performance erbium(Ⅲ) based SMMs.
High residual concentration of arsenic and fluoride is a tricky problem to be solved in the process of reinjection after geothermal water utilization. We develop a method to simultaneously remove As(Ⅴ) and F− from geothermal water using magnetic Fe3O4@MgO adsorbent, fabricated via a one-step method. The effects of pH, contact time, adsorbent dose and temperature on the removal efficiency were investigated systematically. The results show that the Fe3O4@MgO composite has a wide range of pH (2–11), ultrafast removal dynamics (As(Ⅴ): 2 min; F−: 30 min), and high removal efficiency (As(Ⅴ): 99.9%; F−: 96.6%). The adsorption kinetics follows the pseudo-second-order kinetics model, and the adsorption isotherm model fits Freundlich. The adsorption capacity of As(Ⅴ) and F− can reach 123 and 98.4 mg/g, respectively. The exchange of As(Ⅴ) and F− with Mg-hydroxyl groups hydrolysis by MgO was determined the adsorption mechanism. The Fe3O4@MgO adsorbent was capable of achieving the adsorption efficiency as high as 99.9% for As(Ⅴ) and 97.3% for F− in real geothermal water, respectively. Hence, the proposed Fe3O4@MgO composite exhibited as an excellent adsorbent for the remediation of As- and F-contaminated geothermal water.
The discovery of new perovskite compounds under high pressure mainly focuses on the ABO3 compositions and the compositions highly deviated from ABO3 are less explored. Here we demonstrate that the La6Sr3Si6O24 silicate composition can be stabilized as a hexagonal perovskite-related structure with isolated tetrahedra anions under high pressure of 6 GPa. The compound adopts 9-layer shifted hexagonal perovskite-like structure with both B-cation and oxygen deficiencies and contains pseudo-cubic (c′) (La/Sr)O2 layers and hexagonal (h) (La/Sr)O3 layers stacked according to (c′hh)3 sequence. This structure features both B-cation vacancy ordering between the two consecutive hexagonal layers and oxygen vacancy ordering in c′-(La/Sr)O2 layers, resulting in isolated tetrahedral SiO4 anions and ionic conduction behavior. This work demonstrates the practicability of accessing new perovskite-related functional materials from the compositions highly deviated from ABO3 under high pressure.
Inhibitor targeting immune checkpoint is a promising new anticancer therapy. Blocking the interaction between PD-1 and PD-L1 can reverse the immunosuppression state and improve the lethality of immune cells to tumor cells. Here, we report PROTAC-based PD-L1 degraders to enhance T cell killing activity against melanoma. Four series of PD-L1 degraders were designed and synthesized to VHL, CRBN, MDM2 or cIAP E3 ligase system, in which CRBN-ligand-based compound BMS-37-C3 was identified as the most active PROTAC molecule. BMS-37-C3 also significantly enhanced the killing ability of T cells in a co-culture model of A375 and T cells. Furthermore, western blot data and flow cytometry demonstrated that BMS-37-C3 could reduce the protein levels of PD-L1 in dose and time dependent manner, which may provide a new therapeutic method for tumor immunotherapy.
The integrated lipopeptide (RVA)/gene complexes are fabricated with bi-directional regulation on tumor cells and micro-environment. After self-assembling and target coating modification, the poly(γ-glutamic acid) (γ-PGA)/RVA nano-vectors can sequentially respond to pH & redox stimuli, and guarantee efficient therapeutic gene delivery and control release of all-trans retinoic acid. The design provides a facile but promising strategy to treat refractory cancers.
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