Density functional theory study of active sites and reaction mechanism of ORR on Pt surfaces under anhydrous conditions

Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a temperature>100℃.Here,by employing density functional theory calculations,we studied ORR on flat and stepped Pt(111)surfaces with both(110)and(100)type of steps.We found that,in contrast to ORR under hydrous conditions,(111)terrace sites are not active for ORR under anhydrous conditions,because of weakened binding of ORR intermediates induced by O*accumulation on the surface.On the other hand,step edges,which are generally not active for ORR under hydrous conditions,are predicted to be the active sites for ORR under anhydrous conditions.Among them,(110)type step edge with a unique configuration of accumulated O stabilizes O_(2)adsorption and facilitates O_(2)dissociation,which lead an overpotential<0.4 V.To improve ORR catalysts in high-temperature PEMFCs,it is desirable to maximize(110)step edge sites that present between two(111)facets of nanoparticles.

Two-dimensional atomically thin Pt layers on MXenes: The role of electronic effects during catalytic dehydrogenation of ethane and propane

Atomically thin Pt nanolayers were synthesized on the surface of Mo2TiC2 MXenes and used for the catalytic dehydrogenation of ethane and propane into ethylene and propylene,two important chemicals for the petrochemical industry.As compared with Pt nanoparticles,the atomically thin Pt nanolayer catalyst showed superior coke-resistance(no deactivation for 24 h),high activity(turnover frequencies(TOFs)of 0.4–1.2 s^(-1)),and selectivity(>95%)toward ethylene and propylene.The unique Pt nanolayer has a similar geometric surface to Pt nanoparticles,enabling the investigations of the electronic effect on the catalytic performance,where the geometric effect is negligible.It is found that the electronic effect plays a critical role in dehydrogenative product selectivity and catalyst stability.The metal–support interaction is found dependent on the substrate and metal components,providing wide opportunities to explore high-performance MXene-supported metallic catalysts.

Gut commensal metabolite rhamnose promotes macrophages phagocytosis by activating SLC12A4 and protects against sepsis in mice

Sepsis progression is significantly associated with the disruption of gut eubiosis.However,the modulatory mechanisms of gut microbiota operating during sepsis are still unclear.Herein,we investigated how gut commensals impact sepsis development in a pre-clinical model.Cecal ligation and puncture(CLP)surgery was used to establish polymicrobial sepsis in mice.Mice depleted of gut microbiota by an antibiotic cocktail(ABX)exhibited a significantly higher level of mortality than controls.As determined by metabolomics analysis,ABX treatment has depleted many metabolites,and subsequent supplementation with L-rhamnose(rhamnose,Rha),a bacterial carbohydrate metabolite,exerted profound immunomodulatory properties with a significant enhancement in macrophage phagocytosis,which in turn improved organ damage and mortality.Mechanistically,rhamnose binds directly to and activates the solute carrier family 12(potassium-chloride symporter),member 4(SLC12A4)in macrophages and promotes phagocytosis by activating the small G-proteins,Ras-related C3 botulinum toxin substrate1(Rac1)and cell division control protein 42 homolog(Cdc42).Interestingly,rhamnose has enhanced the phagocytosis capacity of macrophages from sepsis patients.In conclusion,by identifying SLC12A4 as the host interacting protein,we disclosed that the gut commensal metabolite rhamnose is a functional molecular that could promote the phagocytosis capacity of macrophages and protect the host against sepsis.

Engineering the high-entropy phase of Pt-Au-Cu nanowire for electrocatalytic hydrogen evolution

Hydrogen economy,as the most promising alternative energy system,relies on the hydrogen production through sustainable water splitting which in turn relies on the high efficiency electrocatalysts.PtAuCu A1-phase alloy has been predicted to be a promising electrocatalyst for the hydrogen evolution.As such preferred phase of Pt-Au-Cu is not thermodynamically favored,herein,we stabilize PtAuCu alloy by engineering the high-entropy phase in the form of nanowire.Density functional theory(DFT)calculations indicate that,in comparison with the ordered phase and segregated phases with discrete hydrogen binding energy,the high-entropy phase provides a diverse combination of site composition to continuously tune the hydrogen binding energy,and thus generate a series of highly active sites for the hydrogen evolution.Reflecting the theoretical prediction,electrochemical tests show that the A1-phase PtAuCu nanowire significantly outperforms its nanoparticle counterpart with phase segregation,toward the electrocatalysis of hydrogen evolution,offering one of the best hydrogen evolution electrocatalysts.

A metabolite from commensal Candida albicans enhances the bactericidal activity of macrophages and protects against sepsis

The gut microbiome is recognized as a key modulator of sepsis development.However,the contribution of the gut mycobiome to sepsis development is still not fully understood.Here,we demonstrated that the level of Candida albicans was markedly decreased in patients with bacterial sepsis,and the supernatant of Candida albicans culture significantly decreased the bacterial load and improved sepsis symptoms in both cecum ligation and puncture(CLP)-challenged mice and Escherichia coli-challenged pigs.Integrative metabolomics and the genetic engineering of fungi revealed that Candida albicans-derived phenylpyruvate(PPA)enhanced the bactericidal activity of macrophages and reduced organ damage during sepsis.Mechanistically,PPA directly binds to sirtuin 2(SIRT2)and increases reactive oxygen species(ROS)production for eventual bacterial clearance.Importantly,PPA enhanced the bacterial clearance capacity of macrophages in sepsis patients and was inversely correlated with the severity of sepsis in patients.Our findings highlight the crucial contribution of commensal fungi to bacterial disease modulation and expand our understanding of the host-mycobiome interaction during sepsis development.

A novel chromogenic and fluorogenic scaffold for detection of oxidative radicals

Radical detection has attracted significant attention recently. Here we have developed a scaffold through covalent assembly principle（OR570）, which could facile applications in detection of oxidative radicals.The primary advantage of the assembly type probe lies at the turn-on fluorescence signal from a zero background and hence high fluorescence turn-on ratio for sensitive detection of weak signal.

Transcriptome-wide identification of differentially expressed genes and long non-coding RNAs in nitroglycerin-tolerant rat aorta

Tolerance to nitroglycerin(GTN)greatly limits its long-time application,and the underlying mechanism remains largely unexplored.In the present study,we aimed to investigate the comprehensive changes in the transcriptome of rat aorta tolerant to GTN by analyzing lncRNA expression.We employed the RNA sequencing(RNA-seq)technique to identify mRNAs and lncRNAs.Ingenuity pathway analysis(IPA)was used for pathway and functional analysis.RT-qPCR was used to validate the RNA-seq results.We identified 22788 genes(reads per kilobase million[RPKM]>0.1,14720 protein-coding genes and 4408 lncRNAs),including 115 differentially expressed(DE)mRNAs(65 up-regulated and 50 down-regulated)and 104 DE lncRNAs(56 up-regulated and 48 down-regulated),in GTN-tolerant aortas.IPA revealed the inhibition of a canonical pathway“Signaling by Rho Family GTPases”and alteration in six upstream regulators.Functional analysis showed that 11 genes were related to“disorder of blood pressure”.We predicted the cis-target genes of DE lncRNAs by the analysis of their neighboring genes.The results revealed the 28 DE lncRNAs adjacent to the 26 protein-coding genes.Many DE mRNAs and cis-target genes of DE lncRNAs have been implicated in the regulation of blood pressure or cell contraction.These results suggested that the dysregulated mRNAs and lncRNAs contributed to the development of GTN tolerance and could serve as potential targets to prevent and reverse GTN tolerance.