Oxygen‑Coordinated Single Mn Sites for Efficient Electrocatalytic Nitrate Reduction to Ammonia

Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection.Here,we report an efficient NitRR catalyst composed of single Mn sites with atomically dispersed oxygen(O)coordination on bacterial cellulose-converted graphitic carbon(Mn-O-C).Evidence of the atomically dispersed Mn-(O-C_(2))_(4)moieties embedding in the exposed basal plane of carbon surface is confirmed by X-ray absorption spectroscopy.As a result,the as-synthesized Mn-O-C catalyst exhibits superior NitRR activity with an NH_(3)yield rate(RNH_(3))of 1476.9±62.6μg h^(−1)cm^(−2)at−0.7 V(vs.reversible hydrogen electrode,RHE)and a faradaic efficiency(FE)of 89.0±3.8%at−0.5 V(vs.RHE)under ambient conditions.Further,when evaluated with a practical flow cell,Mn-O-C shows a high RNH_(3)of 3706.7±552.0μg h^(−1)cm^(−2)at a current density of 100 mA cm−2,2.5 times of that in the H cell.The in situ FT-IR and Raman spectroscopic studies combined with theoretical calculations indicate that the Mn-(O-C_(2))_(4)sites not only effectively inhibit the competitive hydrogen evolution reaction,but also greatly promote the adsorption and activation of nitrate(NO_(3)^(−)),thus boosting both the FE and selectivity of NH_(3)over Mn-(O-C_(2))_(4)sites.

热塑性聚氨酯发泡片材和发泡珠粒成形体的形貌与力学性能的关系

通过不同的发泡工艺和成型工艺制备了密度相近的热塑性聚氨酯发泡片材(TPU-FS)和发泡珠粒成形体(ETPU)材料,研究了2种泡沫材料的形貌与力学性能的关系。通过扫描电镜表征了2种聚氨酯泡沫的结构;利用万能试验机研究了二者的单向压缩性能和循环压缩性能;用旋转流变仪表征了材料在不同压力下的流变性能。研究发现,相近密度下,TPU-FS和ETPU泡沫具有相近的泡孔面积占有率,但是ETPU发泡区域泡孔的平均孔径远大于TPU-FS泡沫;在循环压缩试验中,TPU-FS泡沫具有较高的损耗能和损耗百分比;流变实验中,在不同压力时,ETPU泡沫的储能模量和损耗模量均低于TPU-FS泡沫,且阻尼因子(tanδ)较小,TPU-FS泡沫的tanδ有一定的频率依赖性,而ETPU泡沫的tanδ随频率的变化不明显。同时,对密度相近的TPU-FS泡沫和ETPU泡沫的形貌与损耗百分比的关系进行了初步探讨。

Synergistic catalysis of cluster and atomic copper induced by copper-silica interface in transfer-hydrogenation

To data,using strong metal-support interaction(SMSI)effect to improve the catalytic performance of metal catalysts is an important strategy for heterogeneous catalysis,and this effect is basically achieved by using reducible metal oxides.However,the formation of SMSI between metal and inert-support has been so little coverage and remains challenge.In this work,the SMSI effect can be effectively extended to the inert support-metal catalysis system to fabricate a Cu^(0)/Cu-doped SiO_(2) catalyst with high dispersion and loading(38.5 wt.%)through the interfacial effect of inert silica.In the catalyst,subnanometric composite of Cu cluster and atomic copper(in the configuration of Cu-O-Si)can be consciously formed on the silica interface,and verified by extended X-ray absorption fine structure(EXAFS),in situ X-ray photoelectron spectroscopy(XPS),and high-angle annular dark field-scanning transmission electron microscopy(HAADF-STEM)characterization.The promoting activity in transfer-hydrogenation by the SMSI effect of Cu-silica interface and the synergistic active roles of cluster and atomic Cu have also been revealed from surface interface structure,catalytic activity,and density functional theory(DFT)theoretical calculation at an atomic level.The subnanometric composite of cluster and atomic copper species can be derived from a facile synthesis strategy of metal-inert support SMSI effect and the realistic active site of Cu-based catalyst can also been identified accurately,thus it will help to expand the application of subnanometric materials in industrial catalysis.

Scalable biomimetic SARS-CoV‑2 nanovaccines with robust protective immune responses

Dear Editor,The emergence of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infection requires rapid development of vaccines matching the pace of virus mutation.While the firstgeneration of nucleic acid vaccines have been successful,subunit vaccines carry far fewer safety concerns and also have shown promise in clinical trials.

Polymorphism of Kdo-Based Glycolipids:The Elaborately Determined Stable and Dynamic Bicelles

Understanding how the diversity of glycolipids,including how their chemical structures and composition affect their biological functions,is a remarkable fundamental challenge.In this work,we employed a rare monosaccharide,3-deoxy-Dmanno-2-octulosonic acid(Kdo)to build a simple and biomimetic model to understand the diversity of glycolipids from the viewpoint of supramolecular chemistry.Kdo was chosen not only because its unusual 8-carbon acidic carbohydrate backbone is very different from common hexoses,but also because of its key structural role in lipopolysaccharides and prevalence in bacteria,plant life,and algae.It was found that although both of the two Kdo-lipids S-Kdo and Kdo-S derived from the same carbohydrate backbone and gave bicelles as their self-assembled morphology,experimental results revealed that the self-assembly showed pathway complexity.Bicelle is the thermodynamic product of S-Kdo,while for Kdo-S,the bicelle is only a kinetically trapped state,which finally transforms to a ribbon.Molecular simulation clearly revealed the different packing of Kdo-lipids in the bicelles with different contribution from hydrogen bonds and electrostatic interactions.

Thiol-Disulfide Exchange Coordinates the Release of Nitric Oxide and Dexamethasone for Synergistic Regulation of Intestinal Microenvironment in Colitis

The cell-specific functions of nitric oxide(NO)in the intestinal microenvironment orchestrate its therapeutic effects in ulcerative colitis.While most biomaterials show promise by eliciting the characteristics of NO,the insufficient storage,burst release,and pro-inflammatory side effects of NO remain as challenges.Herein,we report the development of thiol-disulfide hybrid mesoporous organosilica nanoparticles(MONs)that improve the storage and sustained release of NO,broadening the therapeutic window of NO-based therapy against colitis.The tailored NO-storing nanomaterials coordinated the release of NO and the immunoregulator dexamethasone(Dex)in the intestinal microenvironment,specifically integrating the alleviation of oxidative stress in enterocytes and the reversal of NO-exacerbated macrophage activation.Mechanistically,such a synchronous operation was achieved by a self-motivated process wherein the thiyl radicals produced by NO release cleaved the disulfide bonds to degrade the matrix and release Dex via thiol-disulfide exchange.Specifically,the MON-mediated combination of NO and Dex greatly ameliorated intractable colitis compared with 5-aminosalicylic acid,even after delayed treatment.Together,our results reveal a key contribution of synergistic modulation of the intestinal microenvironment in NO-based colitis therapy and introduce thiol-disulfide hybrid nanotherapeutics for the management of inflammatory diseases and cancer.