【作者】 张强；

【导师】 侯士峰；

【作者基本信息】 山东大学 ， 无机化学， 2019， 博士

【摘要】 随着化石燃料消耗量的日益增加及其储量的不断减少,能源和环境问题逐渐增加。燃料电池作为一种新型的绿色能源转换装置具有广泛的应用前景。其中,作为燃料电池的重要组成部分,催化剂材料是目前制备具有优异性能且价格低廉燃料电池的主要技术难点。优化催化剂活性组分的形貌尺寸和载体组成是提高催化剂催化性能的两种重要途径。目前催化剂易受类CO中间产物吸附中毒而导致催化剂性能降低。同时随着储能材料的发展,传统催化剂载体的柔性发展是未来发展方向。柔性材料因其轻便,易携带以及可折叠的性能引起研究者的广泛关注,但柔性电极载体材料负载催化剂用于燃料电池研究鲜有报道。基于此,本论文探索制备各种新型碳纳米材料作为催化剂载体,一方面可提高催化剂催化性能以及稳定性;另一方面制备柔性载体负载催化剂。具体研究内容如下:（1）中空石墨化碳纳米笼材料负载Pd纳米粒子对乙醇的电催化氧化采用氧化镁立方体为模板成功制备新型中空多孔石墨化碳纳米笼（CN）材料作为催化剂载体,随后采用乙醇为还原剂还原制备Pd纳米粒子负载至CN载体制备Pd/CN催化剂。中空石墨化碳纳米笼材料作为载体有助于提高Pd纳米粒子对乙醇催化氧化性能。通过一系列的测试（SEM、TEM、XRD、XPS以及BET）等多种测试方法对催化剂进行表征。通过电化学测试分析所制备的Pd/CN催化剂在碱性条件下对乙醇催化氧化性能,并研究CN作为载体对负载Pd纳米粒子电催化性能影响以及可行性。Pd/CN催化剂对乙醇催化表现出较高的催化活性,其氧化峰的峰电流值为2411.5 mA mg^-1 Pd,分别为Pd/RGO(1308.5 mA mg^-1 Pd)和Pd/C(542.5 mA mg^-1 Pd)催化剂的1.84和4.42倍。同时稳定性测试表明,该Pd/CN复合催化剂表现出良好的稳定性。CN作为载体对提高Pd催化性能起到如下作用:（a）介孔中空结构可提供较大的比表面积;（b）有助于Pd纳米粒子的均匀分散;（c）优异的导电性。（2）多孔PdS_x/C纳米球催化剂的合成及其对乙醇的电催化氧化采用“一锅法”制备聚3,4-乙撑二氧噻吩（PEDOT）纳米球负载Pd纳米粒子,将其高温煅烧制备多孔碳球负载PdS_x催化剂。通过SEM、TEM、HRTEM、XRD、Raman和XPS对产物进行了表征测试。与此同时,系统研究煅烧温度对产物结构以及形貌影响。测试结果表明,煅烧后的碳材料仍维持纳米球形貌,尺寸为2.47±0.60 nm PdS_x纳米粒子均匀负载至纳米多孔球表面。众所周知,催化氧化过程中,硫的存在会导致Pd催化剂中毒,传统PdS催化剂,对乙醇无催化性能。相对于PdS,制备的PdS_x/C多孔纳米球催化剂对乙醇具有催化性能,其峰电流值为162.1 mA mg^-1。催化剂循环伏安扫描1000圈后,其峰电流值仍然维持46.7 mA mg^-1。该工作不仅为乙醇氧化提供了一种新型的燃料电池催化剂,而且为解决催化过程中的硫中毒问题提供了新思路。（3）三维多孔MXene负载Pt纳米粒子对甲醇的电催化氧化采用成本低的聚苯乙烯微球（PS）作为硬模板掺杂至MXene制备出3D多孔MXene材料（e-MXene）,将其作为载体负载Pt制备Pt/e-MXene催化剂研究甲醇催化氧化性能。PS的加入有效阻止MXene堆集从而形成3D多孔结构。e-MXene不仅保持MXene原有属性（优异导电性、良好亲水性以及较强机械稳定性）而且赋予其高比表面积的新特征。通过SEM、TEM、XRD和XPS等方法对所制备的Pt/e-MXene催化剂进行表征测试。电化学测试结果表明,相对于Pt/MXene和JM Pt/C催化剂,Pt/e-MXene催化剂对甲醇具有更高的电催化活性和稳定性,其催化甲醇单位质量电流密度高达798.7 mA mg Pt-1,该数值是Pt/MXene（398.6 mA mg Pt-1）和JM Pt/C（133.43 mA mgPt-1）催化剂的2.1和5.9倍。本工作充分展示了3D大孔MXene结构在甲醇催化氧化性能的优势,并且可将其扩宽至储能、催化、环境以及生物医学领域等方面的应用。（4）三维多孔自支撑石墨烯/碳纳米管柔性膜负载Pt纳米粒子对甲醇的电催化氧化采用成本低的聚苯乙烯微球（PS）作为硬模板掺杂单壁碳纳米管（SWCNT）,制备出高比表面积、优异导电性以及柔韧性的3D多孔石墨烯/单壁碳纳米管柔性自支撑膜材料（e-RGO-SWCNT）。其中,PS的加入可抑制石墨烯的堆叠从而制备三维多孔石墨烯（e-RGO）,SWCNTs贯通e-RGO,从而将其编织成柔性导电膜。随后,载体（e-RGO-SWCNT）负载Pt纳米粒子制备Pt/e-RGO-SWCNT催化剂对其研究甲醇催化氧化性能。通过一系列的测试（SEM、TEM、XPS以及BET）等对催化剂进行表征。电化学测试表明,相对于Pt/e-RGO,Pt/RGO和JM Pt/C催化剂,Pt/e-RGO-SWCNT催化剂表现出更高的电催化活性和甲醇氧化耐久性。这归属于Pt/e-RGO-SWCNT具有较高的比表面积、三维多孔相互连通结构和良好的导电性,更重要的是,Pt/e-RGO-SWCNT在不同弯曲状态（如折叠和扭曲状态）下的电催化性能几乎同非弯曲状态保持一致。更多还原

【Abstract】 With the increasing consumption of fossil fuels and the decreasing reserves,energy and environmental problems are becoming more and more prominent.As a new type of green energy conversion device,fuel cell is an effective choice to solve environmental pollution and energy crisis.Among the fuel cells,catalyst is one of the core components,and it is the main technical barrier for the preparation of high performance and low cost in fuel cell.The catalytic performances of the catalyst can be improved from optimizing the morphological size of precious metals and support composition.The catalysts could be malfunctioned and the catalytic performance would be negatively influenced when there is CO intermediate products present in the system.With the development of energy storage materials,the flexible development of traditional catalyst support is the future direction of fuel cells Developing foldable energy devices with robust mechanical property,portability,foldability and high electrochemical activity has received growing interests.Despite the demand,to our knowledge,there are no reports involving flexible electrodes for fuel cells.In this paper,the novel carbon materials were prepared as supporting for catalysts,which is benefit for improving the anti-toxic and electrocatalytic performance.Moreover,constructing freestanding and flexible carbon materials as support for distributing nanoparticles towards methanol oxidation.The main content in this thesis is listed in the following four aspects:（1）Hollow graphitized carbon nanocage supported Pd catalyst applied in ethanol oxidation reactionHollow graphitized carbon nanocages were developed for improving the electrocatalytic performance of Pd nanoparticles（NPs）towards ethanol oxidation.A mild method was utilized for the preparation of hollow graphitized carbon nanocages（CN）using magnesium oxide as a sacrificial template without high-temperature processing.The Pd/CN catalyst was prepared via a simple reflux procedure,and ethanol served as reductant.The CN can act as high-efficiency support for the distribution of Pd NPs.A set of characterizations,including SEM/TEM,XRD,XPS,BET,among others,were performed to confirm their morphology,composition,and structure.Pd NPs decorated on CN exhibited high catalytic performance with the current density of 2411.5 mA mg^-1 for ethanol oxidation reaction（EOR）,which is 1.84 and 4.42 times higher than reduced graphene oxide（RGO）（1308.5 mA mg’）and C(545.2 mA mg^-1)as supports,respectively.Pd/CN exhibits good durability during the chronoamperometric experiments of long-term durability.The Pd/CN with excellent catalytic performance can be attributed to the CN,including the large surface area with a mesoporous hollow structure,uniform dispersion of Pd NPs,and excellent electrical conductivity.This study may offer new insights for the development of highly effective carbon-based support for applications in ethanol oxidation.（2）PdS_x/C porous nanospheres applied in ethanol oxidation reactionCarbon-supported palladium polysulphide（PdS_x/C）porous nanospheres were prepared by a facile approach to be applied to ethanol oxidation in alkaline medium.The success of this synthesis relies on the preparation of palladium/poly（3,4-ethylenedioxythiophene）（Pd/PEDOT）nanospheres via the reduction of Pd2+by EDOT,followed by calcination at an elevated temperature.A set of characterizations,including SEM,TEM,HRTEM,XRD,Raman,XPS,among others,were performed to confirm their morphology,composition,and structure.The effects of calcination temperature on the structure and morphology of products were systematically investigated by compared samples obtained at different calcination temperatures.It is noteworthy to mention that the calcined product remained spherical shapes when annealed to high temperature.The PdS_x particle size distribution conforms to normal distribution with an average diameter of 2.47 ± 0.60 nm.Tiny nanoparticles are anchored on the surface of PdS_x/C porous nanospheres and distributed homogeneously.It is well known that the Pd catalyst could be malfunctioned and the catalytic performance would be negatively influenced when there is sulfur present in the system.Interestingly,unlike common sulfur-poisoned Pd catalyst,the as-prepared PdS_x/C porous nanospheres were found to show electrocatalytic activity with a value of 162.1 mA mg^-1 for ethanol oxidation in alkaline medium.In particular,the forward peak current intensity achieved 162.1 mA mg^-1 and still kept at 46.7 mA mg^-1 even after 1000 cycles.This work not only prepared a novel catalysts for ethanol oxidation,but also provided a new methods for solving the sulfur-poisoning problem for Pd catalyst in EOR.（3）Pt NPs decorated 3D macroporous Ti₃C₂ MXene Frameworks as a catalyst for high performance methanol oxidation2D Ti₃C₂ MXene sheets were processed into 3D macroporous interconnected embossed architectures（e-MXene）via monodispersed polystyrene（PS）spheres as sacrificial templates to suppress the stack together of MXene sheets,which can be used as skeletons for supporting Pt nanoparticles（Pt/e-MXene）for methanol oxidation.The e-MXene not only mantain the intrinsic properties（such as metallic conductivity,a hydrophilic surface,and good mechanical stability）but also render the new feature of high surface area.A set of characterizations,including SEM,TEM,XRD,XPS,among others,were performed to confirm their morphology,composition,and structure.When used as catalysts for methanol oxidation,the Pt/e-MXene catalysts show much improved performances compared to multilayer MXenes as supporting in terms of electrocatalytic activity and stability,as demonstrated by its peak current density of 798.7 mA mg pt-1 almost two times larger than that of Pt/MXene（398.6 mA mg Pt-1）.This work demonstrates the advantages of 3D macroporous MXene architecture on the electrochemical performance of methanol oxidation and can widen the application of MXene-based materials in the field of energy storage,catalysis,environmental,and biomedical applications.（4）Paper-based porous graphene/single-walled carbon nanotubes supported Pt nanoparticles as freestanding catalyst for electro-oxidation of methanolA freestanding 3D interconnected embossed graphene（e-RGO）-single wall carbon nanotubes（SWCNTs）paper as skeletons for supporting Pt nanoparticles（Pt/e-RGO-SWCNT）without binder,which can be used as a flexible and robust electrode for methanol oxidation.The 3D porous e-RGO was prepared by using monodispersed polystyrene（PS）spheres as sacrificial templates to suppress the re-stacking of RGO sheets.Meanwhile,the SWCNTs penetrated through the e-RGO,and thus weaved them into a scalable film to provide an integrative conductive framework.The Pt/e-RGO-SWCNT is expected to show excellent electrocatalytic activities toward MOR.A set of characterizations,including SEM/TEM,XRD,XPS,and BET,among others,were performed to confirm their morphology,composition,and structure.Benefited from their high surface area,3D porous interconnected architecture,and good electrical conductivity,the Pt/e-RGO-SWCNT catalyst exhibited much higher electrocatalytic activity and durability for methanol oxidation than Pt/e-RGO and Pt/RGO catalysts.More importantly,the Pt/e-RGO-SWCNT is demonstrated to be outstanding flexible electrocatalysts,and the electrocatalytic performances under the different distorted situation（such as folded and rolled states）are almost the same as the normal state.更多还原