Improving the Efficiency of Water Splitting and Oxygen Reduction Via Single-Atom Anchoring on Graphyne Support

Single-atom catalysts(SACs)have received significant interest for optimizing metal atom utilization and superior catalytic performance in hydrogen evolution reaction(HER),oxygen evolution reaction(OER),and oxygen reduction reaction(ORR).In this study,we investigate a range of single-transition metal(STM_(1)=Sc_(1),Ti_(1),V_(1),Cr_(1),Mn_(1),Fe_(1),Co_(1),Ni_(1),Cu_(1),Zr_(1),Nb_(1),Mo_(1),Ru_(1),Rh_(1),Pd_(1),Ag_(1),W_(1),Re_(1),Os_(1),Ir_(1),Pt_(1),and Au_(1))atoms supported on graphyne(GY)surface for HER/OER and ORR using first-principle calculations.Ab initio molecular dynamics(AIMD)simulations and phonon dispersion spectra reveal the dynamic and thermal stabilities of the GY surface.The exceptional stability of all supported STM_(1)atoms within the H1 cavity of the GY surface exists in an isolated form,facilitating the uniform distribution and proper arrangement of single atoms on GY.In particular,Sc_(1),Co_(1),Fe_(1),and Au_(1)/GY demonstrate promising catalytic efficiency in the HER due to idealisticΔG_(H^(*))values via the Volmer-Heyrovsky pathway.Notably,Sc_(1)and Au_(1)/GY exhibit superior HER catalytic activity compared to other studied catalysts.Co_(1)/GY catalyst exhibits higher selectivity and activity for the OER,with an overpotential(0.46 V)comparable to MoC_(2),IrO_(2),and RuO_(2).Also,Rh_(1)and Co_(1)/GY SACs exhibited promising electrocatalysts for the ORR,with an overpotential of 0.36 and0.46 V,respectively.Therefore,Co_(1)/GY is a versatile electrocatalyst for metal-air batteries and water-splitting.This study further incorporates computational analysis of the kinetic potential energy barriers of Co_(1)and Rh_(1)in the OER and ORR.A strong correlation is found between the estimated kinetic activation barriers for the thermodynamic outcomes and all proton-coupled electron transfer steps.We establish a relation for the Gibbs free energy of intermediates to understand the mechanism of SACs supported on STM,/GY and introduce a key descriptor.This study highlights GY as a favorable single-atom support for designing highly active and cost-effective versatile electrocatalysts for practical applications.

Spatio-temporal evolution characteristics and pattern formation of a gas–liquid interfacial AC current argon discharge plasma with a deionized water electrode

A discharge ignited by an AC power source in contact with deionized water as one of the electrodes is investigated.Immediately after initiation,the discharge exhibits a unique phenomenon:the gas-phase discharge is extended into the liquid.Later,a cone-like structure is observed at the liquid surface.Synchronous monitoring of current–voltage characteristics and liquid properties versus time suggests that the discharge shapes are functions of the liquid properties.The spatio-temporal profiles indicate the potential effects of water,ambient air impurities,and metastable argon on the discharge chemistry.This becomes more obvious near the liquid surface due to increasing production of various transient reactive species such as centerdot OH and NO centerdot.Moreover,it is revealed that thermalization of the rotational population distributions of the rotational states(N′⩽6,J′⩽13/2)in the Q1 branch of the OH(A2Σ+,υ′=0→X2Π3/2,υ′′=0)band ro-vibrational system is influenced by the humid environment near the liquid surface.In addition,the transient behaviors of instantaneous concentrations of long-lived reactive species(LRS)such as H2O2,NO−2,and NO−3 are observed with lengthening the discharge time.The production of multiple transient and LRS proposes AC excited gas–liquid argon discharge as a potential applicant in industrial wastewater cleaning,clinical medicine,and agriculture.

Physicochemical properties of the AC- excited helium discharges using a water electrode

In this paper, the AC-excited helium discharges generated between the powered needle electrode enclosed in a conical quartz tube and the grounded de-ionized water electrode are investigated. The current and voltage waveforms exhibit a transition from the glow-like to streamer-like mode discharges, which forms a stable cone-shaped structure at the gas-liquid interface. In this region, the air and water vapor diffusion initiate various physical-chemical processes leading to substantial changes of the primary species emission intensities （e.g., OH, N2, NO, and O） and the rotational temperatures. The experimentally measured rotational temperature at the gas-liquid interface is 870 K from the Nz（C-B） band with a power input of 26 W. With the prolongation of the discharge time, significant changes in the discharge voltage and current, discharge emission patterns, instantaneous concentrations of the secondary species （e.g., H202, NO2, and NO3） in the liquid phase, pH values and electrical conductivities of the liquids are observed experimentally. The present study is helpful for deepening the understandings to the basic physical-chemical processes in the discharges in contact with liquids, especially to those occurring in the vicinity of the gas-liquid interface, and also for promoting existing and potential applications of such type of discharges in the fields of environmental protection, biomedicine, agriculture, and so on.

Characteristics of a radio-frequency cold atmospheric plasma jet produced with a hybrid cross-linear-field electrode configuration

Cold atmospheric plasma(CAP)jet has wide applications in various fields including advanced materials synthesis and modifications,biomedicine,environmental protection and energy saving,etc.Appropriate control on the volume,temperature and chemically reactive species concentratio ns of the CAP jet is of great importance in actual applications.In this paper,an radio-frequency atmospheric-pressure glow discharge(RF-APGD)plasma generator with a hybrid cross-linear-field electrode configuration is proposed.The experimental results show that,with the aid of the copper mesh located at the downstream of the traditional co-axial-type plasma generator with a cross-field electrode configuration,a linear field between the inner powered electrode of the traditional plasma generator and the copper mesh can be established.This linerfield can,to some extent,enhance the discharges at the upstream of the copper mesh,resulting in small increments(all less than 12.5%)of the species emission intensities,electron excitation temperatures and gas temperatures by keeping other parameters being unchanged.And due to the intrinsic transparent and conducting features of the grounded copper mesh to the gas flowing,electric current and heat flux of the plasma plumes,a plasma region with higher concentrations of chemically reactive species and larger plasma plume diameters is obtained at the downstream of the grounded copper mesh on the same level of the gas temperature and electron excitation temperature compared to those of the plasma free jet.In addition,the charged particle number densities at the same downstream axial location of the grounded copper mesh decrease significantly compared to those of the plasma free jet.This means that the copper mesh is also,to some extent,helpful for separating the chemically reactive neutral species from the charged particles in side a plasma environment.The preceding results indicate that the cross-linear-field electrode configuration of the plasma generator is an effective approach for tuning the characteristics of the RF-APGD plasma jet in order to obtain an appropriate combination of the plasma jet properties with higher chemically reactive species concentrations,especially relative higher number densities of neutral species,larger plasma volumes and lower gas temperatures.

Influences of the inner diameter of the solid shielding tube on the characteristics of the radio-frequency cold atmospheric plasma jet

Active control of the local environment of the cold atmospheric plasma(CAP) jet is of great importance in actual applications since the CAP operates in an open atmosphere with the inevitable entrainment of the surrounding cold air. In this paper, the solid shielding effects of the cylindrical quartz tubes with different inner diameters on the characteristics of the CAP jets driven by a radio-frequency(RF) power supply are studied experimentally. The experimental results show that the total length of the shielded plasma jet can be increased significantly by an appropriate combination of the quartz tube inner diameter and that of the plasma generator nozzle exit with other parameters being unchanged. This phenomenon may be qualitatively attributed to the loss of diffusion of the charged particles in the radial direction under different inner diameters of the quartz tubes. Compared with the plasma free jet, the plasma shielding jet is produced with optimized parameters including longer plasma jet length, higher concentrations of chemically reactive species, higher rotational, vibrational, and electron excitation temperatures when the inner diameters of the solid shielding tube and the generator nozzle exit are the same. A maximum plasma jet length of 52.0 cm is obtained in contrast to that of 5.0 cm of the plasma free jet in this study. The experimental results indicate that the solid shielding effect provides a new method for the active control of the local environment of the RF-CAP jet operating in an open atmosphere.

Traditional ethno-botanical uses of medicinal plants from coastal areas of Pakistan

Objective:To document the traditional uses of wild plants as medicine by the villagers along the coastal highway from Karachi to Uthal.Methods:Information presented in this research was gathered from the local people using an integrated approach of floral collections,discussions with the elderly people and traditional medicinal practitioners using semi-structured questionnaire.Results:27 families in the targeted area.Majority of the plants(54%)from this coastal plant diversity were xerophytes followed by halophytes/xero-halophytes(40%)and glycophytes(6%).The most important uses included gastrointestinal diseases,pain killer,arthritis,skin and sexual disorders,asthma and expectorant.The above-ground parts of plants i.e.leaf,stem and fruit/seed as decoction are used most commonly to cure 23 ailments but root was also used in some cases.Conclusions:Ethno-medicinal surveys indicated the medicinal importance of 54 plant species from phyto-medicinal claim and it is hoped that it will lead to detailed chemical and pharmacological evaluations.This may also lead to a discovery of novel bioactive compounds for food and pharmaceutical industries.This study helps in documenting therapeutic uses of herbal remedies with new pevhayltou-amtioendsic.iTnhali sc lmaiamy aanldso i tl iesa hdo tpoe da tdhiastc iot vweirlyl loeaf dn otov edle tbaiioleadc tcihveem ciocmalp aonudn pdhs afromr afcoooldog aicnadl pharmaceutical industries.