Towards electrochemical hydrogen storage in liquid organic hydrogen carriers via proton-coupled electron transfers

Green hydrogen is identified as one of the prime clean energy carriers due to its high energy density and a zero emission of CO_(2).A possible solution for the transport of H_(2)in a safe and low-cost way is in the form of liquid organic hydrogen carriers(LOHCs).As an alternative to loading LOHC with H_(2)via a two-step procedure involving preliminary electrolytic production of H_(2)and subsequent chemical hydrogenation of the LOHC,we explore here the possibility of electrochemical hydrogen storage(EHS)via conversion of proton of a proton donor into a hydrogen atom involved in covalent bonds with the LOHC(R)via a protoncoupled electron transfer(PCET)reaction:2nH^(+)+2ne^(-)+Rox■n H_(2)^(0)Rred.We chose 9-fluorenone/fluorenol(Fnone/Fnol)conversion as such a model PCET reaction.The electrochemical activation of Fnone via two sequential electron transfers was monitored with in-situ and operando spectroscopies in absence and in presence of different alcohols as proton donors of different reactivity,which enabled us to both quantify and get the mechanistic insight on PCET.The possibility of hydrogen extraction from the loaded carrier molecule was illustrated by chemical activation.

Trinuclear Nickel Catalyst for Water Oxidation:Intramolecular Proton-Coupled Electron Transfer Triggered Trimetallic Cooperative O-O Bond Formation

We report a molecular trinuclear nickel(TNC-Ni)catalyst for water oxidation that exhibited high catalytic performance and stability under neutral conditions(pH 7).Electrochemical studies disclosed that cooperation among the three nickel sites plays a vital role in both charge accumulation and O-O bond formation.This TNC-Ni catalyst could accomplish 4e−oxidation of water by involving all three nickel sites and the O-O bond formation was triggered by a charge distribution process from 5 to 5_(dp) via proton-coupled electron transfer.

Activation of Transition Metal(Fe,Co and Ni)-Oxide Nanoclusters by Nitrogen Defects in Carbon Nanotube for Selective CO_(2) Reduction Reaction

The electrochemical carbon dioxide reduction reaction(CO_(2)RR),which can produce value-added chemical feedstocks,is a proton-coupled-electron process with sluggish kinetics.Thus,highly efficient,cheap catalysts are urgently required.Transition metal oxides such as CoO_(x),FeO_(x),and NiO_(x)are low-cost,low toxicity,and abundant materials for a wide range of electrochemical reactions,but are almost inert for CO_(2)RR.Here,we report for the first time that nitrogen doped carbon nanotubes(N-CNT)have a surprising activation effect on the activity and selectivity of transition metal-oxide(MO_(x)where M=Fe,Ni,and Co)nanoclusters for CO_(2)RR.MO_(x)supported on N-CNT,MO_(x)/N-CNT,achieves a CO yield of 2.6–2.8 mmol cm−2 min−1 at an overpotential of−0.55 V,which is two orders of magnitude higher than MO_(x)supported on acid treated CNTs(MO_(x)/O-CNT)and four times higher than pristine N-CNT.The faraday efficiency for electrochemical CO_(2)-to-CO conversion is as high as 90.3%at overpotential of 0.44 V.Both in-situ XAS measurements and DFT calculations disclose that MO_(x)nanoclusters can be hydrated in CO_(2)saturated KHCO_(3),and the N defects of N-CNT effectively stabilize these metal hydroxyl species under carbon dioxide reduction reaction conditions,which can split the water molecules and provide local protons to inhibit the poisoning of active sites under carbon dioxide reduction reaction conditions.

CRISPR/Cas9-mediated knockout of SLC15A4 gene involved in the immune response in bovine rumen epithelial cells

The objective of this study was to determine the role of SLC15A4 in the muramyl dipeptide(MDP)-mediated inflammatory response of bovine rumen epithelial cells(BRECs).First,changes in the m RNA expression of proinflammatory factor genes in BRECs following 10μg m L^(–1)MDP treatments were examined.RT-q PCR results showed that the expression of pro-inflammatory factor(IL-1β,IL-6,and TNF-α)m RNAs were significantly increased under MDP stimulation(P<0.001).Moreover,SLC15A4-Knockout(SLC15A4-KO)cells were obtained through lentivirus packaging,transfection,screening,and cell monoclonal culture.In order to gain further insight into the potential function of SLC15A4,we utilized transcriptome data,which revealed a change in the genes between WT-BRECs and SLC15A4-KO.Five down-regulated pro-inflammatory genes and 13 down-regulated chemokine genes related to the inflammatory response were identified.Meanwhile,the down-regulated genes were mostly enriched in the nuclear factorκB(NF-κB)and mitogen-activated protein kinase(MAPK)signaling pathways.The results of RT-q PCR also verified these detected changes.To further determine the mechanism of how WT and SLC15A4-KO BRECs are involved in inflammatory responses,we investigated the inflammatory responses of cells exposed to MDP.WT-BRECs and SLC15A4-KO were treated with a culture medium containing 10μg m L^(–1)MDP,in comparison to a control without MDP.Our results show that SLC15A4-KO BRECs had reduced the expression of genes(IL-6,TNF-α,CXCL2,CXCL3,CXCL9,and CCL2)and proteins(p-p65 and p-p44/42)from the MDP-mediated inflammatory response compared to WT-BRECs(P<0.05).In this experiment,CRISPR-Cas9 was used to KO the di/tripeptide transporter SLC15A4,and its role was confirmed via the MDP-induced inflammatory response in BRECs.This work will provide a theoretical basis for studying the pro-inflammatory mechanism of MDP and its application in the prevention and treatment of subacute rumen acidosis in dairy cows.

CuSx-mediated two reaction systems enable biomimetic photocatalysis in CO_(2) reduction with visible light

The performances of heterogeneous catalysts can be effectively improved by optimizing the catalysts via appropriate structure design.Herein,we show that the catalysis of cuprous sulfide can be boosted by constructing the hybrid structure with Cu_(2)S nanoparticles on amorphous CuSx matrix(Cu_(2)S/CuSx).In the photocatalytic CO_(2) reduction under visible light irradiation,the Cu_(2)S/CuSx exhibited a CO production rate at 4.0μmol h-1 that is 12-fold higher than that of the general Cu_(2)S catalyst.Further characterizations reveal that the Cu_(2)S/CuSx has two reaction systems that realize the biomimetic catalysis,involving in the light reaction on the Cu_(2)S nanoparticle-CuSx matrix heterojunctions for proton/electron production,and the dark reaction on the defect-rich CuSx for CO_(2) reduction.The CuSx matrix could efficiently activate CO_(2) and stabilize the split hydrogen species to hinder undesired hydrogen evolution reaction,which benefits the proton-electron transfer to reduce CO_(2),a key step for bridging the two reaction systems.

Engineering adjacent Fe_(3)C as proton-feeding centers to single Fe sites enabling boosted oxygen reduction reaction kinetics for robust Zn-air batteries at high current densities

Oxygen reduction reaction(ORR)plays an important role in the next-generation energy storage technologies,whereas it involves the sluggish and complicated proton-coupled electron transfer(PCET)steps that greatly limit the ORR kinetics.Therefore,it is urgent to construct an efficient catalyst that could simultaneously achieve the rapid oxygen-containing intermediates conversion and fast PCET process but remain challenging.Herein,the adjacent Fe_(3)C nanoparticles coupling with single Fe sites on the bubble-wrap-like porous N-doped carbon(Fe_(3)C@FeSA-NC)were deliberately constructed.Theoretical investigations reveal that the adjacent Fe_(3)C nanoparticles speed up the water dissociation and serve as proton-feeding centers for boosting the ORR kinetics of single Fe sites.Benefiting from the synergistic effect of the Fe_(3)C and single Fe sites,the Fe_(3)C@FeSA-NC affords an excellent half-wave potential of 0.88 V,and enables the assembled Zn-air batteries with the high peak power density of 164.5 mW·cm^(-2)and long-term stability of over 200 h at high current densities at 50 mA·cm^(-2).This work clarifies the mechanism for improving ORR kinetics of single atomic sites by engineering the adjacent proton-feeding centers,shedding light on the rational design of cost-effective electrocatalysts for energy conversion and storage technologies.

Redox-neutral photocatalytic strategy for selective C–C bond cleavage of lignin and lignin models via PCET process

It remains challenging to achieve the selective cleavage of C–C bonds in lignin or lignin model compounds to produce aromatic products in high yield and selectivity.We have developed a redox-neutral photocatalytic strategy to accomplish this goal in both b-O-4 and b-1 lignin models at room temperature(RT)via proton-coupled electron transfer(PCET)process without any pretreatments of substrate,by adjusting the alkalinity of base to obtain a lignin models/base PCET pair with a bond dissociation free energy close to 102 kcal/mol.Without breaking down C_b–Ccbond and any C–O bonds,this PCET method is 100%atom economy and produces exclusive Ca–C_bbond cleavage products,such as benzaldehydes(up to 97%)and phenyl ethers(up to 96%),in high to excellent yields and selectivities.Preliminary studies indicated that the PCET strategy is also effective for the depolymerization of native lignin at RT,thus providing significantly important foundation to the depolymerization of lignin.

The upregulated intestinal folate transporters direct the uptake of ligand-modified nanoparticles for enhanced oral insulin delivery

Transporters are traditionally considered to transport small molecules rather than large-sized nanoparticles due to their small pores.In this study,we demonstrate that the upregulated intestinal transporter(PCFT),which reaches a maximum of 12.3-fold expression in the intestinal epithelial cells of diabetic rats,mediates the uptake of the folic acid-grafted nanoparticles(FNP).Specifically,the upregulated PCFT could exert its function to mediate the endocytosis of FNP and efficiently stimulate the traverse of FNP across enterocytes by the lysosome-evading pathway,Golgi-targeting pathway and basolateral exocytosis,featuring a high oral insulin bioavailability of 14.4%in the diabetic rats.Conversely,in cells with relatively low PCFT expression,the positive surface charge contributes to the cellular uptake of FNP,and FNP are mainly degraded in the lysosomes.Overall,we emphasize that the upregulated intestinal transporters could direct the uptake of ligand-modified nanoparticles by mediating the endocytosis and intracellular trafficking of ligand-modified nanoparticles via the transporter-mediated pathway.This study may also theoretically provide insightful guidelines for the rational design of transporter-targeted nanoparticles to achieve efficient drug delivery in diverse diseases.

Promotion of the oxygen evolution performance of Ni–Fe layered hydroxides via the introduction of a proton-transfer mediator anion

Developing efficient catalysts with high durability and activity for the oxygen evolution reaction(OER)is imperative for sustainable energy conversion technologies,including hydrogen generation and CO_(2) reduction,as well as other electrochemical energy storage systems.To this end,a comprehensive understanding of the mechanism for the water oxidation reaction is vital.Herein,a surfactant,nonafluoro-1-butanesulfonate(FBS),was introduced into Ni-Fe layered double hydroxide(Ni Fe-FBS/CFP)via electrochemical deposition on the surface of a carbon fiber paper(CFP)substrate.The as-prepared Ni Fe-FBS/CFP electrode exhibited excellent catalytic activities for OER compared to the Ni-Fe layered double hydroxide based electrode(Ni Fe-LDH/CFP),an excellent stability of 15 h,and an ultralow Tafel slope of 25.8 m V dec-1.Furthermore,by combining the results of p H-dependent kinetics investigations,chemical probing,proton inventory studies,and isotopic and atom-protontransfer measurements,it was observed that a proton-transfer process controls the reaction rates of both the Ni Fe-LDH and Ni Fe-FBS catalysts,and the residual sulfonate groups serve as proton transfer mediator to accelerate the proton transfer rate.

Photocatalyst-controlled and visible light-enabled selective oxidation of pyridinium salts

This study proposes two different methods of photocatalytic-controlled and visible light-induced selective oxidation of pyridiniums with air as the terminal oxidant.The key to these transformations is to choose the appropriate light source and photocatalyst.Pyridiniums are successfully converted into pyrroles through oxygen-mediated cycloaddition,proton-coupled electron transfer(PCET),pyridine ring opening,and recyclization.The other route is that pyridiniums selectively form 4-carbonyl pyridines through free radical rearrangement/aerobic oxidation under the catalysis of cobalt(Ⅱ).

Mechanical Trapping of the Phlorin Intermediate

Trapping unstable intermediates for elucidating reaction mechanisms in chemistry presents a formidable challenge.There has long been a lack of direct evidence for key intermediates like the highly reactive phlorin leading to porphyrin.Here,we report a molecular-strain engineering(MSE)strategy that harnesses intramolecular strain to trap the native phlorin during porphyrin synthesis.By mechanically constraining its periphery,a phlorin stable towards oxidation was captured as an isolable intermediate and fully characterized.

Synthesis of Quaternary Carbon-Centered Benzoindolizidinones via Novel Photoredox-Catalyzed Alkene Aminoarylation: Facile Access to Tylophorine and Analogues

Photoredox-catalyzed aminoarylation and thioami-nation of unactivated alkenes have been developed,providing novel synthetic routes to access synthe-tically challenging quaternary carbon-centered benzoindolizidinones and trifluoromethylthiolated piperidines using readily available starting materials.Notably,these transformations were enabled by merging amidyl radical generation from N-alkyl benzamides with oxidant incorporation.Density functional theory calculations were performed to understand the reaction mechanism and to rationa-lize the regioselectivities.Moreover,the newly deve-loped catalytic aminoarylation provided a convenient synthetic route for natural product tylophorine and its gem-dimethyl analogues with greatly improved drug-like properties such as enhanced solubility and stability.

A Strategy of Stabilization via Active Energy-Exchange for Bistable Electrochromic Displays

As future energy-saving optoelectronics,bistable electrochromic(EC)materials/devices have high energy efficiency for potential applications as smart windows,displays,and information/energy storage,due to their ability tomaintain optical states without consuming energy.However,further development is hindered by the lack of in-depth understanding of related key factors and universally applicable design strategies to achieve bistability.