| With the continuous development of the world economy and industry,human beings are facing many enormous challenges such as environmental pollution and energy shortage.Among all the challenges,the water crisis has seriously jeopardized many places in the world.The problem of solving the shortage of fresh water resources is imminent.Desalination of seawater or salt water is an important means to solve the water crisis.Capacitive deionization(CDI)is a new type of desalination technology based on the theory of electric double layer capacitance(EDLC).It has the core advantages of environmental protection,low cost,easy maintenance and no secondary pollution.The core and key of this technology is to find high-performance electrode materials.The ideal electrode material should have high specific surface area,proper pore structure,good electrical conductivity and chemical stability.Graphene is an electrode material with great potential for CDI application due to its large theoretical specific surface area and excellent electrochemical properties.However,the stacking effect between the layers of graphene sheets makes it difficult to achieve ideal surface area and pore structure,which severely restricts its electrochemical performance,desalination capacity and lower charge efficiency.Based on the above research hotspots and problems,this paper mainly prepares three-dimensional graphene-based electrode materials by means of heteroatom doping,chemical activation and metal compound recombination from the perspective of modified graphene aerogel(GA).The desalting performance,charge efficiency and cycle stability of the graphene-based electrode during deionization were qualitatively and quantitatively investigated,as well as some key factors,such as voltage,flow rate,influent concentration and operating mode.The specific research contents are as follows:1.Preparation of nitrogen-doped graphene aerogel(NGA)with a large number of microporous structures by hydrothermal method,followed by activation of phosphoric acid,annealing and activation of graphene,etching of some micropores to obtain microporous/mesoporous cross structure.The results show that the specific surface area of nitrogen-doped graphene aerogel after phosphoric acid activation(PGA)increases to 574.14 m3 g-1,the capacitance increases to 177.19 F g-1 and the interlayer stacking effect of graphene sheets is significantly weakened.In the desalination experiment,the effects of voltage,concentration and flow rate on the adsorption capacity were investigated.It was found that the adsorption/desorption rate of the PGA electrode was significantly higher than that of the pure graphene aerogel,and the high desalination capacity remained at 20.93 mg g-1 after 30 cycles with great stability.2.Preparation of manganese dioxide nanospheres through the hydrothermal reaction and introduced the particles into the graphene sheet layer while induced the formation of manganese dioxide nanowires.Finally,graphene aerogel/MnO2 nanowire composite(MnGA)was successfully prepared.After analysis,it was found that manganese dioxide nanowires can effectively reduce the stacking effect between graphene sheets,and obtain excellent specific capacitance(145.42 F g-1).Under constant pressure mode,the electrosorption capacity reaches at 25.78 mg g-1.The influence of factors such as voltage,concentration and flow rate were highly investigated.Then based on the properties of BiOC1 which can specifically adsorb/desorb chloride ions and high capacitance and adsorption capacity of MnGA,we construct a hybrid Hybrid Capacitive Deionization(HCDI).While applying constant current,the differences of HCDI in adsorption performance,stability and charge efficiency under different operating modes were studied and the principle of HCDI was further investigated with the help of electrochemical test results.The results show that the HCDI composed of MnGA and BiOC1 electrodes has excellent electrosorption capacity(69.18 mg g-1)and charge efficiency up to 75.21%with good regenerability after 30 cycles. |
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