【作者】 王星；

【导师】 杨上峰；

【作者基本信息】 中国科学技术大学 ， 材料学， 2025， 博士

【摘要】 富勒烯作为碳元素家族中继金刚石和石墨之后被科学界确认的第三种同素异形体,因其明确的分子结构和卓越的物理和化学性质而备受关注。然而本征的零维富勒烯易发生团聚,限制了其实际应用。富勒烯因其独特的中空笼状结构和大π共轭电子结构,成为构筑自组装功能材料的理想基元。富勒烯分子可借助溶液自组装策略,通过范德华力或π-π作用,构建具有不同维度与形貌的组装材料,极大地丰富了富勒烯材料的结构类型。这些组装材料在结合富勒烯本征特性的同时,因其维度和形貌特点而展现出更加丰富的性质,拓宽了富勒烯的应用前景。然而,对于少层或单层富勒烯二维组装材料的构筑,传统的自组装策略面临着挑战。一方面,富勒烯在无空间约束的自由组装过程中容易沿三维方向无序堆叠,导致材料厚度难以控制;另一方面,富勒烯分子间相互作用力较弱,常见的二维共价材料的剥离方法易导致整体结构的破坏,从而难以将其剥离为少层或单层的二维纳米片。鉴于此,本论文集中于富勒烯C60二维组装材料的制备和应用研究,分别通过基于二维模板材料层间限域的非共价组装策略和基于C60共价聚合的共价组装策略,构筑了少层或单层的C60二维组装材料,深入探究了 C60二维组装材料的几何结构、吸电子效应、能带结构和电子缓冲作用等物理化学性质,并探索了其在储能、气体分离、光催化和电催化等领域中的应用潜力,主要开展了以下四个方面的工作:(1)C60在自组装过程中的三维无序堆叠特性阻碍了少层或单层C60二维非共价自组装材料的形成。针对这一问题,我们以具备较大层间距的二维MXene材料作为模板,利用低温水热法将C60插入少层MXene层间限域空间,构建了C60@MXene杂化材料,实现了 C60二维非共价组装。通过一系列光谱和结构表征,证实了 C60通过N-Ti键与MXene共价锚定并插入层间,扩大了 MXene的层间距(12.8 (?)到14.1 (?)),从而抑制了 MXene自发堆叠。进一步地,将C60@MXene应用于钠离子电池(SIB)负极材料,其电化学性能显著优于原始MXene,在10000次长循环测试后具有高达94.5%的容量保持率,表现出优异的循环稳定性。性能提升源于C60的刚性球形结构扩大了 MXene的层间距,为离子存储提供更多活性位点和空间;同时C60的吸电子效应和有序组装网络的形成加快了电荷传输动力学。通过理论计算进一步揭示了 C60插层诱导的层间距扩大显著降低了钠离子扩散势垒。(2)C60的二维非共价自组装材料的优异性质驱使我们进一步探索更加稳定的C60二维共价组装材料的构筑和性能。基于此,我们以C60为结构基元,通过共价聚合策略构建了 C60二维共价组装材料,并利用直接液相剥离法实现了少层二维C60(2D-C60)纳米片的制备。通过一系列形貌及结构表征,揭示了 2D-C60的晶体结构和结构稳定性,其中C60通过C-C单键和[2+2]环加成键与相邻四个C60共价连接,形成独特的周期性多孔结构与通道特征。进一步地,针对传统聚合物气体分离膜中渗透性与选择性的制约效应,以及现有二维材料因气体通道不可控导致的分离效率受限等挑战,我们采用溶液浇铸法,将2D-C60与自具微孔聚合物PIM-1混合,构建了基于2D-C60的混合基质膜。气体渗透实验结果表明,2D-C60的周期性多孔结构和锯齿形层间通道为CO2提供了快速的气体扩散通道,并选择性阻隔了 N2,实现了高效的CO2/N2选择性分离。所制备的PIM-(2D-C60)-0.5 wt%混合基质膜的CO2渗透系数(11458.3 Barrer)和CO2/N2选择性(61.5)均提升至纯PIM-1膜3倍左右,性能跨越了 2008年Robeson上限和2019年上限,并优于绝大多数已报道的混合基质膜的性能。此外,2D-C60纳米片的引入提升了 PIM-1膜的抗物理老化和抗塑化性能。(3)传统光催化产过氧化氢(H2O2)的方法依赖牺牲剂以促进电荷分离,存在成本高、产物污染及分离复杂等问题,且现有研究多局限于两电子的水氧化(WOR)或两电子氧还原(ORR)反应的单一路径,难以实现在无牺牲剂体系下的高效双路径协同催化。基于此,我们利用少层2D-C60共价网络自身特征的能带结构和优异的电荷分离和传输能力,展示了 2D-C60在无牺牲剂的纯水中通过协同双路径光催化合成H2O2的能力。通过结构表征,我们揭示了 2D-C60的能带结构完全覆盖了两电子ORR和两电子WOR的电位区间(VB:1.43 V CB:0.13V vs.NHE),满足双路径H2O2生成的热力学需求。可见光照射下,在N2和O2饱和的纯水中,H2O2产率分别为268和683μmolg-1h-1。电子自旋共振(ESR)自旋捕获实验验证了 2D-C60通过协同WOR和ORR双路径实现H2O2的高效合成,并揭示了四电子WOR产生的O2作为两电子ORR底物的级联反应路径。通过光电化学测试系统,揭示了 2D-C60快速的电荷分离和转移能力。(4)在碱性析氢反应(HER)中,钌(Ru)基催化剂亲氧性强,其对氢(H)和羟基(OH)中间体物种的强吸附导致活性位点中毒及反应动力学迟滞,制约了其实际应用。针对这一问题,我们利用少层2D-C60作为Ru纳米颗粒(NPs)的载体,构筑了独特的金属-载体相互作用。利用2D-C60的电子缓冲作用,通过可逆的电子转移机制调控了金属活性位点的电荷密度,实现了对多中间体吸附强度的协同优化,从而提高了催化性能。电催化测试结果表明,Ru NPs/2D-C60催化剂在碱性HER(1M KOH)中表现出优于商用Pt/C的性能,其本征活性较纯RuNPs提升8倍。此外,Ru NPs/2D-C60表现出优异的长期稳定性以及在阴离子交换膜水电解槽(AEMWE)中的应用潜力。动力学研究和理论计算结果证实,基于2D-C60的电子缓冲作用,2D-C60与Ru和H/OH中间体之间的可逆电荷转移过程调控了 Ru活性位点电荷密度的变化,削弱了H/OH中间体在Ru表面的结合强度,从而加速了 HER动力学过程,提高了 HER活性。更多还原

【Abstract】 Fullerenes,the third allotrope of carbon after diamond and graphite to be scientifically recognized,have attracted significant attention due to their well-defined molecular structure and exceptional physical and chemical properties.However,the tendency of zero-dimensional fullerenes to aggregate severely limits their practical applications.The hollow cage-like structure and extensive π-conjugated electron system of fullerenes make them ideal building blocks for constructing self-assembled functional materials.Leveraging solution-based self-assembly strategies,fullerenes can flexibly form diverse dimensional and morphological materials through van der Waals forces or π-π interactions,significantly enriching the structural diversity of fullerenebased materials.These assembled materials not only retain the intrinsic properties of fullerenes but also exhibit enhanced functionalities due to their specific dimensionality and morphology,significantly broadening their application prospects.However,constructing few-layer or monolayer two-dimensional fullerene assemblies presents challenges.On one hand,fullerenes tend to undergo uncontrolled three-dimensional stacking during free assembly,making it difficult to control thickness.On the other hand,the weak intermolecular interactions between fullerenes make common exfoliation methods for 2D covalent materials likely to damage the overall structure,thus hindering the production of few-layer or single-layer 2D nanosheets.Given these challenges,this dissertation focuses on the construction and application exploration of two-dimensional fullerene assembly materials.Through the non-covalent assembly strategy based on the interlayer confinement of two-dimensional template materials and the covalent assembly strategy based on the covalent polymerization of fullerenes,we successfully constructed few-layer or monolayer two-dimensional fullerene assemblies.The research systematically investigated the unique physicochemical properties of these assemblies,including their geometric configurations,electron-withdrawing effects,band structures,and electron buffering effects,across diverse application domains such as energy storage,gas separation,photocatalysis,and electrocatalysis.These findings significantly expand the application scope of fullerenes.The following four aspects of work have been mainly carried out:(1)The intrinsic three-dimensional disordered stacking behavior of fullerene(C60)during self-assembly poses a significant challenge to the controllable synthesis of fewlayer or monolayer two-dimensional non-covalent C60 architectures.To address this issue,we utilized 2D MXene with large interlayer spacing as a template.Through a low-temperature hydrothermal process,C60 molecules were intercalated into the confined interlayer space of MXene,successfully fabricating C60@MXene hybrid materials and thereby achieving 2D non-covalent assembly of C60.Spectroscopic and structural characterizations confirmed that C60 is covalently anchored to MXene via NTi bonds and inserted between the layers,expanding the interlayer spacing from 12.8(?) to 14.1 (?),effectively suppressing the spontaneous stacking of MXene.As a sodiumion battery anode,C60@MXene demonstrates superior electrochemical performance over pristine MXene,exhibiting exceptional cycling stability with 94.5%capacity retention after 10,000 cycles.The performance improvement stems from the rigid spherical structure of C60,which expands the interlayer spacing of MXene,increases the number of active sites,and provides more space for ion storage.Simultaneously,C60’s electron-withdrawing effect and ordered assembly network optimize charge transfer kinetics.Theoretical calculations reveal that C60 intercalation-induced interlayer expansion increases significantly reduces diffusion barriers.(2)The exceptional properties of the two-dimensional non-covalent selfassembled materials of C60 drive us to further explore the construction and performance investigation of more stable two-dimensional covalent assembly materials of fullerene.Based on this,we used C60 as the building block and constructed C60 covalently assembled materials via covalent polymerization strategy.We then employed direct liquid-phase exfoliation method to produce few-layer 2D-C60 nanosheets.Through a series of morphological and structural characterizations,we revealed the crystal structure and structural stability of 2D-C60,wherein each C60 is covalently linked to four adjacent C60 molecules via C-C single bonds and[2+2]cycloaddition bonds,forming a unique periodic porous structure with characteristic channels.Furthermore,to address the trade-off between permeability and selectivity in traditional polymer gas separation membranes and the limited efficiency of existing 2D materials due to uncontrolled gas channels,we fabricated a 2D-C60-based mixed matrix membrane by blending 2D-C60 with a polymer of intrinsic microporosity(PIM-1)using a solution casting method.Gas permeation tests demonstrated that the periodic porous architecture and zigzag interlayer channels of 2D-C60 provide efficient diffusion pathways for CO2 while selectively blocking N2,achieving superior CO2/N2 separation performance.The PIM-(2D-C60)-0.5 wt%membrane exhibited a CO2 permeability of 11458.3 Barrer and CO2/N2 selectivity of 61.5,both～3 times higher than pure PIM-1,surpassing both the 2008 Robeson upper bounds and the 2019 upper bounds and outperforming the vast majority of reported mixed-matrix membranes.Additionally,2D-C60 enhanced the membrane’s resistance to physical aging and plasticization.(3)Traditional photocatalytic H2O2 production relies on sacrificial agents for charge separation,leading to high costs,product contamination,and complex purification.Furthermore,existing research is predominantly limited to single-pathway catalysis via either two-electron water oxidation(WOR)or oxygen reduction(ORR),hindering efficient dual-pathway synergistic catalysis in sacrificial agent-free systems Leveraging the intrinsic band structure and superior charge separation/transport properties of few-layer 2D-C60 covalent networks,we demonstrate its ability for synergistic dual-pathway photocatalytic H2O2 synthesis in pure water without sacrificial agents.Through structural characterization,we revealed that the energy band structure of 2D-C60 fully covers the potential range of the two-electron oxygen reduction reaction(ORR)and two-electron water oxidation reaction(WOR)(VB:1.43 V,CB:0.13 V vs.NHE),satisfying the thermodynamic requirements for dual-pathway H2O2 generation.Under visible light,H2O2 production rates were 268 and 683 μmol g1 h-1 in N2 and O2-saturated pure water,respectively.ESR spin-trapping experiments confirmed efficient H2O2 synthesis via synergistic WOR and ORR pathways,revealing a cascade reaction where O2 from the four-electron WOR serves as a substrate for the two-electron ORR.Photoelectrochemical tests highlighted the rapid charge separation and transfer capabilities of 2D-C60.(4)In alkaline hydrogen evolution reaction(HER),Ru-based catalysts suffer from excessive oxophilicity,where strong adsorption of hydrogen(H)and hydroxyl(OH)intermediates leads to active site poisoning and sluggish reaction kinetics,limiting their practical applications.To address this,we introduced few-layer 2D-C60 as a novel support for Ru nanoparticles(NPs),establishing unique metal-support interactions.Leveraging the electron buffering capability of 2D-C60,its dynamic reversible electron transfer mechanism modulates the charge density of metal active sites,enabling synergistic optimization of intermediate adsorption strength and enhanced catalytic performance.Electrocatalytic tests reveal that the Ru NPs/2D-C60 catalyst exhibits superior performance to commercial Pt/C in alkaline HER(1 M KOH),with an intrinsic activity 8 times higher than that of pure Ru NPs.Moreover,it demonstrates excellent long-term stability and promising potential for application in anion exchange membrane water electrolyzers(AEMWE).Kinetic studies and theoretical calculations confirm that the reversible charge transfer between 2D-C60,Ru,and H/OH intermediates,facilitated by the electron buffering effect of 2D-C60,modulates the charge density of Ru active sites.This weakens the binding strength of H/OH intermediates on Ru surfaces,thereby accelerating HER kinetics and enhancing HER activity.更多还原