Study On The Adsorption And Aggregation Behaviors Of Graphdiyne In Aqueous Environment And Its Properties For Water Electrolysis

The extensive consumption of fossil fuels has resulted in severe energy crises and environmental pollution.Developing efficient nanomaterials is a pathway with tremendous potential to address these challenges.Graphdiyne（GDY）,as a unique carbon isomer consisted of the hybrid sp-and sp^2-carbons,which endows it with highly conjugatedπ-πstructure,rich carbon-carbon bonds,adjustable electronic structure,unique physical and chemical properties,strong mechanical properties,and excellent electrical conductivity.Since its development by Li Yuliang in 2010,GDY has garnered significant attention and been used in the fields of energy,catalysis,environment,and biomedicine.The preparation and application of GDY based nanomaterials is an emerging research hotspot,but the mass production and application of GDY will lead to more GDY entering the water environment.At the same time,it is reported that GDY based materials have certain biological cytotoxicity,which will eventually lead to potential ecological risks.Therefore,when studying the application of GDY in energy environment and other fields,it is also necessary to deeply study the environmental behavior of GDY in water,so as to accurately assess the migration,transformation and risk of GDY in the environment.In order to study the environmental behavior and application of GDY in water environment,the following related studies have been carried out:1)The adsorption effects of aromaticity and substituents on the adsorption and aromatization of GDY were systematically investigated.It is found that the adsorption affinity of aromatic compounds by GDY and graphene enhanced with the increasing number of aromatic rings due toπ-πinteraction.Graphene preferred to adsorb the electron-substituted catechol due to theπ-πinteraction,while GDY was more likely to adsorb the electron-substituted nitrobenzene.The enhanced adsorption of nitrobenzene to GDY was mainly attributed to the favoredπ-πelectron-donor-acceptor（EDA）interaction between theπ-acceptor adsorbate aromatic compounds and the electron-rich environment of GDY.The proposed adsorption enhancement mechanisms were further tested through the adsorption isotherm and the density function theory（DFT）calculation.These results will increase the understanding of the mechanism of GDY to absorb organic pollutants from water,and advance to understand the adsorption behavior of GDY in aqueous environment,and provide reliable data for assessing the ecological risk of graphdiyne in water environment.2)The effect of cations,pH,and natural organic matter on the aggregation of GDY in water was studied.Trends in the aggregation of GDY are consistent with classical DLVO theory,and the critical coagulation concentrations of cations follow the order of monovalent cations（Na⁺,168 m M）>divalent(Ca²⁺,3.82 m M;Mg²⁺,4.72 m M)>trivalent(La³⁺,0.09 m M;Ce³⁺0.10 m M).An increase in solution p H from acidic（p H=4）to basic（p H=10）results in a significant decrease in aggregation kinetics of GDY due to electrostatic repulsion.Natural organic matter can increase the stability of GDY through steric effect,and the structural index of natural organic matter is correlated with the CCC value of GDY.The CCC value of GDY is positively correlated with Aromatic value,FI,and SUVA₂₅₄,but negatively correlated with E₂/E₃and HIX.These structural indices can be used as convenient indicators to evaluate the stability of GDY effected by natural organic matter.3)The aggregation and sedimentation of graphdiyne and fullerene(C₆₀)were investigated in the dark and under light.Trends in the aggregation of GDY and C₆₀in the absence of light are consistent with the classical Derjaguin–Landau–Verwey–Overbeek theory,and this is the first report of critical coagulation concentration values in environmental cations for GDY.Simulated sunlight irradiation promoted the aggregation of GDY and C₆₀in the presence of divalent cation,which was obvious even in the presence of natural organic matter.a presumable mechanism for the light-accelerated aggregation of GDY and C₆₀was proposed.Under illumination,GDY and C₆₀absorbed the simulated sunlight energy,promoting Brownian motion by photothermal conversion then enhancing the collision probability,leading to a lower apparent barrier and thus a higher sedimentation rate constant（k）in the presence of light.These results provide a novel mechanism for the light-accelerated aggregation of carbon-based nanomaterials and increase the understanding of the sunlight-induced aggregation behaviors of GDY and C₆₀with important implications for their potential environmental fate in natural waters.4)The water electrolysis performance of graphdiyne was studied.A nanohybrid of Fe Ni-MOF/GDY was fabricated by the incorporation of graphdiyne and an Fe Ni-based metallic organic framework（Fe Ni-MOF）.The introduction of GDY reduced the charge cycle barrier of Fe Ni-MOF/GDY by partial reduction of the iron atoms deeply embedded in Fe Ni-MOF,which was confirmed by XPS,M?ssbauer spectroscopy,and XAS.The reduced Fe in Fe Ni MOF/GDY was easily oxidated to the key intermediate Fe OOH*during OER.DFT and in situ Raman analysis showed that the second step in the OER was the rate-determining step.Based on the efficient OER and HER,Fe Ni-MOF/GDY exhibited a small cell voltage of overall water splitting(1.50 V and 1.57 V at 10 and 100 m A cm^-2)and was therefore an effective electrocatalyst.The present study expands the application of GDY to modulate embedded active sites of MOFs and paves the way for preparing high-performing catalysts in the energy conversion field.