Sulfur doped iron-nitrogen-hard carbon nanosheets as efficient and robust noble metal-free catalysts for oxygen reduction reaction in PEMFC

Transition metal-nitrogen-carbon(M-N-C)as a promising substitute for the conventional noble metalbased catalyst still suffers from low activity and durability for oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs).To tackle the issue,herein,a new type of sulfur-doped ironnitrogen-hard carbon(S-Fe-N-HC)nanosheets with high activity and durability in acid media were developed by using a newly synthesized precursor of amide-based polymer with Fe ions based on copolymerizing two monomers of 2,5-thiophene dicarboxylic acid(TDA)as S source and 1,8-diaminonaphthalene(DAN)as N source via an amination reaction.The as-synthesized S-Fe-N-HC features highly dispersed atomic Fe Nxmoieties embedded into rich thiophene-S doped hard carbon nanosheets filled with highly twisted graphite-like microcrystals,which is distinguished from the majority of M-N-C with soft or graphitic carbon structures.These unique characteristics endow S-Fe-N-HC with high ORR activity and outstanding durability in 0.5 M H_(2)SO_(4).Its initial half-wave potential is 0.80 V and the corresponding loss is only 21 m V after 30,000 cycles.Meanwhile,its practical PEMFC performance is a maximum power output of 628.0 mW cm^(-2)and a slight power density loss is 83.0 m W cm^(-2)after 200-cycle practical operation.Additionally,theoretical calculation shows that the activity of Fe Nxmoieties on ORR can be further enhanced by sulfur doping at meta-site near FeN_(4)C.These results evidently demonstrate that the dual effect of hard carbon substrate and S doping derived from the precursor platform of amid-polymers can effectively enhance the activity and durability of Fe-N-C catalysts,providing a new guidance for developing advanced M-N-C catalysts for ORR.

High-performance proton exchange membrane fuel cell with ultra-low loading Pt on vertically aligned carbon nanotubes as integrated catalyst layer

Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.

Recent Technologies for the Extraction and Separation of Polyphenols in Different Plants:A Review

Polyphenol is an important secondary metabolite with unique physiological functions and biological activity.The polyphenols in different plants and biomass have different chemical structures,which needs various extraction methods to obtain them.Recently,plant polyphenols and their application research in food and medicine have become a research hotspot,which is mainly focused on preparation,purification,structural identification,and biological activity assays.Among these researches,extraction and separation are the key sections to investigate the structure and activity of polyphenol.Hence,this review summarized the recent extraction and separation techniques of polyphenol,including solvent extraction,supercritical fluid extraction,ultrasonic extraction,enzymatic extraction,resin adsorption extraction,and electric field method,etc.In addition,this review also reveals the current problems and proposes future extraction research of polyphenol.It is hoped that this review will provide a guide for the researchers who are actively committed to promoting progress in the field of polyphenolics.

The electrical parameters measurement system for electrotome output based on Labview

An accurate detection of the effective values of electric voltage and current from high frequency power generators is a precondition for the development of smart electrotomes. In this light, an energy detection system based on personal computer (PC) is developed hereby. It senses voltage and current in isolation from generators with transformers, and then the measured values are amplified, filtered, transformed into single-ended signals and converted to RMS. The detected signals are transformed into digital signals through Data Acquisition Card (DAQ) and the data are processed with quadratic fit in Labview. Finally, the controller completes constant power output. The experiment results indicate that the energy detection system can measure the output parameters precisely and the controller can achieve constant power control.

Protective effects of lignin fractions obtained from grape seeds against bisphenol AF neurotoxicity via antioxidative effects mediated by the Nrf2 pathway

Lignin exhibits antioxidative and various other biological properties.However,its neuroprotection capability has rarely been studied.In this study,three types of lignin with different structures were prepared from grape seeds by using different isolation techniques.The antioxidative and neuroprotective effects of the lignin fractions were evaluated with the apoptosis model of murine neuroectodermal(NE-4C)neural stem cells stimulated with bisphenol AF.The results demonstrated that the half maximal inhibitory concentration for scavenging 2,2-diphenyl-1-picrylhydrazyl with water-soluble lignin(L-W,58.19μg·mL^(–1))was lower than those of lignin in the autohydrolyzed residue of grape seeds(84.27μg·mL^(–1))and original lignin in grape seeds(99.44μg·mL^(–1)).BPAF exposure had negative effects on the reactive oxygen species,malondialdehyde content,and superoxide dismutase and glutathione peroxidase activities in NE-4C cells,which can be reversed by using the prepared lignin to reduce oxidative stress.An immunofluorescence assay demonstrated that grape seed lignin induced protective effects on BPAF-injured NE-4C cells via the nuclear factor erythroid 2-related Factor 2 pathway.In addition,correlational analyses showed that lignin(L-W)with lower molecular weights and noncondensed phenolic hydroxyl group content and higher contents of COOH groups effectively prevented cell apoptosis,scavenged reactive oxygen species,and ensured protection from nerve injury.This study demonstrated that grape seed lignin can be used as a neuroprotective agent and serves as a demonstration of active lignin production from grape seed waste.

Steady-state Voltage Reactive Compensation Method for Half-wavelength Transmission Lines Considering Equivalent Power Supply Impedance

Half-wavelength AC transmission(HWACT)refers to transmission along lines with an electrical distance of half the power frequency wavelength.The voltage amplitude at the sending terminal is equal to that at the receiving terminal in steady-state.Furthermore,the voltage at the receiving terminal does not vary with load.However,the electrical distance has been extended in actual HWACT lines because of the impact of the equivalent power supply impedance,so the attractive characteristics no longer hold.As a result,reactive power compensation methods with constant power factor and constant voltage are needed and these are presented in this paper.The steady-state operational characteristics,the calculation methods of additional reactive power compensation and the admittance of a controllable shunt reactor are also given.The methods proposed in this paper are relatively simple to implement,and the calculations involved are straightforward,resulting in effective voltage stabilization.The results indicate that such compensation methods can increase the transmission capacity while maintaining a relatively low voltage along the line.

Evaluation of fiber degree for fish muscle based on the edge feature attention net

The fiber mouthfeel of fish muscle is a highly sought-after goal for surimi gel products.The primary aim of research and development has been to quickly and accurately evaluate fiber degree for fish muscle.Therefore,based on the ResNet model,edge feature attentional mechanism was introduced to obtain the edge feature attention net (EFANet) to evaluate fiber degree for fish muscle.The EFANet was trained and tested on a dataset,which was made by collecting microscopic pictures of fish samples with different degrees of breakage.Compared with the three classic convolutional neural network (CNN) models,the EFANet emphasizes the learning of fiber texture information for fish muscle,reduces the effect of image color change,and significantly improves the detection accuracy.The average accuracy and specificity of the EFANet-50 on the testing dataset were 96.22% and 97.92%,respectively,which proved that it can effectively predict the fiber degree of fish muscle.

Underlying mechanisms of the antagonistic effects of Bifidobacterium adolescentis CCFM1108 on Penicillium expansum:Based on comparative transcriptome analysis

Penicillium expansum is the primary postharvest pathogen that attacks fruits and vegetables and threatens human health.Bifidobacterium adolescentis CCFM1108 has been previously demonstrated to inhibit the growth of Penicillium expansum and patulin production;however,its modes of action remain unclear.RNA-seq analysis was used to investigate the underlying antifungal mechanism of metabolites produced by B .adolescents CCFM1108.The expression of genes in the control group and three treatment groups (1/2 MIC CFS,1/4 MIC CFS,and acid treatment groups) was determined and further compared using GO and KEGG analyses.The inhibitory metabolites were found to participate in the dysfunction of the mitochondrial membrane,affecting energy metabolism,reactive oxidative species production,and patulin biosynthesis.Compared with the mixture of multiple metabolites of Bifidobacterium ,the acid mixture affected gene expression in a more significant manner by inhibiting all critical genes included in the patulin biosynthetic pathway.The changes in the patulin biosynthetic were verified by qRT-PCR in the presence of acids.Collectively,the present study provides a clear perspective on the antifungal mechanism of metabolites produced by a B.adolescents strain through transcriptome analysis and suggests that acid mixtures could be potential candidates for the postharvest control of P .expansum .