【作者】 王莹；

【导师】 李朝林；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2023， 硕士

【摘要】 海水淡化技术作为解决淡水资源匮乏的重要手段,受到了广泛关注。其中,海水淡化电池技术因其能耗低、二次污染小、基建成本低等优点成为海水淡化领域的研究热点。然而,其高效储氯电极的匮乏严重限制了其发展与应用。具有高理论除盐容量的铋材料被认为是极具应用前景的储氯电极材料,但其在储氯过程存在体积膨胀大、储氯产物电导率低等问题,导致除盐过程中的循环稳定性差。针对上述问题,本课题提出通过碳掺杂改性提升铋的储氯性能,比选了多种掺杂方式并对最优的金属有机骨架化合物(Metal-Organic Frameworks,MOFs)衍生的铋碳材料进行系统研究,随后以磷酸钛钠为储钠电极,构建并优化了海水淡化电池。具体研究内容如下:为提高铋材料的导电性与结构稳定性,本课题采用三种碳掺杂改性方式。第一种改性方式将铋纳米颗粒与碳纳米管进行机械混合;第二种改性方式为通过喷雾干燥的方式将铋源和碳纳米管充分混合,再通过高温退火的方式形成碳包覆的铋材料;第三种改性方式为构建铋金属有机框架(Bi-MOF)结构并退火合成铋锚固在碳骨架上的材料。结果证实碳掺杂是一项有效的改性方式。将三种碳掺杂方式进行对比,发现MOFs衍生的铋碳材料具有最优异的电化学性能。进一步优化MOFs衍生的铋碳材料的合成工艺,结果显示700℃退火2 h的条件下合成的铋碳材料具有最优的性能。铋碳材料可逆性良好,在电流密度为500m A/g下除盐容量高达141.9 mg/g,循环两百圈容量稳定在90 mg/g左右,容量保持率为66.9%。铋碳材料倍率性能良好,在1000 m A/g的大电流密度下除盐容量为106.1 mg/g。此外,铋碳材料可在0.05 mol/L至2 mol/L的较宽范围浓度下正常工作,最佳工作浓度范围为0.2～0.6 mol/L。铋碳材料展现出的高除盐性能归结于铋碳材料稳定的结构。平均粒径为120 nm的铋球锚固在碳骨架上,碳骨架构建出的高比表面积与低孔径的结构缓解材料反应过程中发生的体积膨胀,并为电子与离子提供了丰富的传输通道。将上述铋碳电极作为储氯电极,磷酸钛钠电极作为储钠电极,构建海水淡化全电池,分析离子交换膜、电极质量比与溶液p H等因素对电池除盐性能的影响。结果表明:在阴阳离子交换膜均存在,铋碳与磷酸钛钠电极质量比为1:1,且处于p H为2的环境下,海水淡化电池最高除盐量可达66.0 mg/g,十圈循环后容量保持在30.3 mg/g。良好的除盐性能证明,本课题成功制备了具有海水淡化应用价值的铋碳电极。更多还原

【Abstract】 As an important technology to alleviate the problem of lack of available water resources,seawater desalination technologies have been widespread concerned.Among them,desalination battery technology has become a research hotspot in the field of desalination because of its advantages of low energy consumption,low secondary pollution and low infrastructure cost.However,the lack of high-efficiency chlorine storage electrode kinds seriously limits the development and application of desalination battery.Bismuth,with its high theoretical desalination capacity,is considered to be the promising chlorine storage electrode material.However,bismuth has many problems such as large volume expansion and low conductivity of its chlorine storage products,resulting in the poor cycle stability in the desalination process.In order to solve the above problems,this project proposes to improve the chlorine storage performance of bismuth by carbon doping modification,and then choose the best method from a variety of doping methods.After that,the optimal MOFs-derived bismuth carbon material is systematically studied.Finally,the desalination battery is constructed and optimized by using sodium titanium phosphate as the sodium storage electrode.The specific research content is as follows:To improve the conductivity and structural stability of bismuth materials,three carbon doping modification methods are adopted in this project.The first modification method is to mechanically mix bismuth nanoparticles with carbon nanotubes.The second modification method is to fully mix the bismuth source and carbon nanotubes by spray drying,and then form a carbon-coated bismuth material by high-temperature annealing.The third modification method is to construct the Bi-MOF(metal-organic framework)structure and anneal the material that bismuth is anchored on a carbon skeleton.The results confirm that carbon doping is an effective modification method.Comparing the three carbon doping methods,it is found that the bismuth carbon material derived from MOFs had the best electrochemical performance.The synthesis process of bismuth carbon materials derived from MOFs is further optimized,and the results show that the bismuth carbon materials synthesized under the condition of annealing at 700 °C for 2 h had the best performance.First,bismuth carbon materials have good reversibility.At a current density of 500 m A/g,the desalination capacity is as high as 141.9 mg/g,and the capacity of two hundred cycles is stable at around 90.0 mg/g.Capacity retention rate is 66.9%.Moreover,bismuth carbon materials have good magnification performance,for the desalination capacity could be106.1mg/g at a high current density of 1000 m A/g.In addition,bismuth carbon materials can work normally in a wide range of concentrations from 0.05 mol/L to 2mol/L,and the optimal working concentration range is 0.2～0.6 mol/L.The high desalination performance of bismuth carbon materials is due to the stable structure of bismuth carbon materials.Bismuth spheres with an average particle size of 120 nm are anchored to the carbon skeleton,which constructs a structure with high specific surface area and low pore size to alleviate the volume expansion,and provides abundant transport channels for electrons and ions.To construct a seawater desalination full battery,the above-mentioned bismuth carbon electrode is used as the chlorine storage electrode and sodium titanium phosphate electrode is used as the sodium storage electrode.And then,the effects of ion exchange membrane,electrode mass ratio and solution p H on the desalination performance of the battery are analyzed.The results show that when in a solution of sodium chloride at p H 2,the mass ratio of bismuth carbon and sodium titanium phosphate electrode is 1:1 with the presence of anion and cation exchange membranes,the maximum salt removal capacity of the desalination battery can reach 66.0 mg/g,and the capacity remains at 30.3 mg/g after ten cycles.The excellent desalination performance indicates that a well prepared bismuth carbon material with desalination application potential is achieved in this project.更多还原