【作者】 刘成；

【导师】 李有勇； 孙宝全；

【作者基本信息】 苏州大学 ， 材料科学与工程， 2021， 博士

【摘要】 为了满足人类日益增长的能源需求,同时减少对化石燃料的依赖并减轻其对环境的影响,人类迫切需要开发具有成本效益和环境友好型的储能设备。锂电池(LiBs)是目前能够满足上述性能指标且具有足够的技术成熟度的先进储能体系之一。但由于锂离子电池的极限能量密度较低,即使将锂离子电池的性能开发至最佳也无法满足人类对能源的需求。在众多的能源储能设备中,硫锂(Li-S)电池作为新一代锂离子电池的升级,突破锂电池的能量密度极限,可以达到更高的理论比容量,是目前最具前景的能量储存设备之一;另一方面,燃料电池作为一种将化学能直接转化为电能的设备逐渐受到人们的重视。因为不需要进行燃烧,没有热量的消耗的同时燃料利用率大大增强,所以燃料电池也被认为是“终极能源电池”。基于第一性原理计算,本论文研究了二维多孔材料以及二元合金材料在上述两种电池中的应用潜力。通过不同的催化剂性能改性策略,从理论角度研究了材料催化性能提升的内在机制。第三章中,利用材料改性策略中合金化与浓度效应,分别研究Ni-Fe,Co-Fe合金材料在锂硫电池中的应用。通过电子性质分析探讨其性能提升的原理。计算结果表明,Fe表面与多硫化物中间体存在极强的结合能。这种过强的结合能虽然可以有效抑制溶液中多硫化物的穿梭效应,但也阻碍了多硫化物的持续锂化过程,使得电池的电流密度明显降低。Co和Ni的加入可以有效降低材料表面与多硫化物的结合。电子结构分析表明,Co和Ni的掺杂使得合金表面原子d带中心降低,d带电子被填充,使得吸附能降低。第四章探讨了二维TMD材料MoS2在燃料电池氧还原反应中的应用潜力。根据材料改性策略中的浓度效应,讨论了不同P掺杂浓度对催化性能的影响。DFT计算结果表明,P掺杂浓度为5.5%的结构比3.7%的更稳定。在不同掺杂浓度下,P-MoS2表现出不同的电化学氧还原催化活性。随着P掺杂浓度的增加,表面的活性位点也在增加,促使氧气可以稳定地吸附和解离。在发展新型能源电池的同时,高效的氢气制备也同样重要。相比于传统的化石燃料裂解产氢,以电为动力的电化学产氢方式显得更加环保且可持续。所以在第五章内容中,我们提出了一组用于电化学分解水的催化剂设计方案。通过比较不同尺寸的Cu基纳米核壳颗粒组份,探讨了纳米颗粒的尺寸效应和不同的边界效应对析氢反应催化活性的影响。搭建了以Fe、Ru和Os为核心组分的Mx@Cu55-x(x=1,13)核壳纳米团簇,并计算了其结构参数、稳定性和电子性能。结果显示,尺寸效应和边界效应共同作用于氢在团簇表面的吸附,形成竞争关系。同时将W掺杂的RuO2固溶体作为电解水的析氧反应催化剂,探讨了合金化效应对RuO2在析氧反应中催化性能的影响。结果显示,合金化使RuO2表面出现额外活性位点。酸性条件下,不同的H+浓度促使W/RuO2二元合金氧化物表面呈现不同的析氧反应催化活性。更多还原

【Abstract】 In order to meet the increasing energy demand,while reducing the dependence on fossil fuels and reducing the environmental pollution,it is urgent for human beings to develop cost-effective and environment-friendly energy storage equipment.Lithium batteries(LiBs)is one of the advanced energy storage systems which can meet the above performance indexes and have sufficient technical maturity.Because of the low limit energy density,even if lithium ion batteries are developed to the best of their performance,they can not meet human energy needs.Among the numerous energy storage devices,lithium-sulfur(Li-S)batteries,an upgraded generation of lithium ions,can break through the energy limitation of lithium batteries and achieve even higher capacity theoretically.On the other hand,fuel cell,a kind of equipment which can directly convert chemical energy into electric energy,has been paid more and more attention.Because of the high efficiency and no heat consumption,fuel cell is considered to be the "ultimate energy".With first principles calculation,this thesis discussed the application potential of binary alloy materials and two-dimensional materials in the above two kinds of batteries.Based on different modification strategies in catalyst,we explored the insight into improving performance of catalytic activity.In chapter 3,we studied the application of Ni-Fe,Co-Fe alloy materials in lithiumsulfur batteries according to the alloying and concentration effects in the material modification strategy.And then,the improved performances were discussed with the analysis of electronic properties.Corresponding results indicated the strong binding energy between Fe and polysulfides.Although this strong binding energy can effectively inhibit the shuttle effect of poly sulfide in solution,it also hinders the lithiation process of polysulfide,which makes the current density of the battery decrease obviously.The addition of Co and Ni can effectively reduce the binding energy of polysulfide.The electronic structure analysis shows that,with the filling of electrons in d band,doping of Co and Ni can decrease the d band center,leading to the decreasing of adsorption energy.In chapter 4,we explored the potential application of two-dimensional TMD materials MoS2 in oxygen reduction reactions.According to the concentration effect in the material modification strategy,the influence of different concentration P doping on the catalytic performance is discussed.DFT calculation results show that the structure with a P doping concentration of 5.5%is more stable than 3.7%of that structure.Meanwhile,P doped MoS2 shows different ORR catalytic activity under different doping concentrations.The active sites increase with the increasing of doping concentration.In that case,oxygen can be adsorbed and dissociated stably.While developing new energy batteries,efficient hydrogen preparation is equally important.Compared with the traditional hydrogen production from fossil fuel cracking,electro-powered hydrogen production through electrochemical reaction is more environmentally friendly and sustainable.Therefore,in Chapter 5,we propose a set of catalyst design schemes for electrochemical decomposition of water.This part discussed the size effect and surface boundary effect on HER catalytic activity by comparing Cu based nanoparticles with different sizes.Mx@Cus5-x(x=1,13 and M=Fe,Ru and Os)core-shell nanoparticles were designed.After that,we discussed the stability and electronic properties cording to DFT calculation for each particles.The result shows that the size effect and the boundary effect act on the adsorption of hydrogen on the surface of the cluster at the same time and form a competitive relationship.The W doped RuO2 solid solution was also used as the OER catalyst for electrolytic water to explore the effect of alloying effect on the catalytic performance of RuO2 in oxygen evolution reaction.Results indicated that alloying results in additional active sites on the surface.Under acidic conditions,different H+concentrations induce different OER catalytic activity on the surface of binary alloy oxides.更多还原