【作者】 赵君；

【导师】 邓意达； 潘相敏；

【作者基本信息】 天津大学 ， 工程（专业学位）， 2023， 博士

【摘要】 能源危机和环境污染问题迫使人类开发清洁、可再生的新型能源替代传统化石能源。电催化技术可以结合新能源技术,将低价值化学品转换成生产和生活中必需的高价值化学品,因此受到广泛关注。电催化剂和反应器件对于实现高效的电催化反应至关重要。在众多电催化剂中,钴基电催化材料具有成本低、电催化性能较好的优势,展现出广阔的应用前景。此外,电催化反应的效率、活性以及稳定性等与反应器件密切相关。当前,电催化性能不能满足社会生产需求。因此,本文设计了高性能钴基电催化剂,应用于电解水析氢反应（hydrogen evolution reaction,HER）、析氧反应（oxygen evolution reaction,OER）和氧还原反应（oxygen reduction reaction,ORR）,揭示了电催化剂结构-性能之间的构效关系。同时,搭建了新型碱性膜电解水器件,将实验室电催化剂应用于新型器件,为催化材料从实验室走向实际应用以及电解水器件的发展提供了技术途径。首先,本论文采用掺杂策略优化尖晶石型氧化物的活性位点。通过水热法制备了原子级厚度的二维（2D）尖晶石型Ni掺杂Co₃O₄（Ni-Co₃O₄）,并将制备的Ni-Co₃O₄应用于OER和ORR。电化学测试结果表明,Ni-Co₃O₄纳米片具有双功能氧催化性能,OER的过电位为275 m V,ORR的起始电位为0.92 V。分析结果表明,Ni掺杂有助于形成氧空位,并促进电子从Ni离子向Co离子转移。最终,作为ORR催化活性位点的Co²⁺和作为OER催化活性位点的Ni³⁺的含量增加。此外,2D纳米结构和Ni掺杂有助于促进OER过程电子转移,原位拉曼（Raman）表征证明OER过程中真正的活性组分更偏向于Ni离子。本工作为制备高活性、耐久性的尖晶石型过渡金属氧化物双功能氧催化剂提供了策略。其次,设计复合材料,调控活性位点的电子结构,是优化电催化性能的有效策略。本论文通过构建高活性界面调控氢氧化钴复合材料的电催化性能。采用共沉淀法和化学浸渍法分别制备了a和β相氢氧化钴（a/β-Co（OH）₂）及负载钌复合材料（Ru/Co（OH）₂）,并将制备的复合材料应用于碱性HER。电化学测试结果显示Ru/α-Co（OH）₂具有良好的HER催化性能,显著优于Ru/β-Co（OH）₂的活性。当电流密度为-10 m A cm^–2时,Ru/α-Co（OH）₂的HER活性与商业Pt/C相当,在大电流密度下,其HER活性明显优于Pt/C。研究表明,制备的α-Co（OH）₂纳米片有利于Ru团簇均匀、高密度分散,并在界面处形成了Ru–O–Co键。密度泛函理论计算表明,相比于Ru/β-Co（OH）₂,Ru/α-Co（OH）₂中较长的Ru–O–Co键优化了水解离和OH^-解吸的自由能,促进了Volmer反应步骤,加速了碱性HER动力学。本章工作为设计高活性复合电催化剂提供了策略。当前商业电解水制氢的效率、电流密度和启停特性等无法满足国家氢能技术发展需求。碱性阴离子交换膜（anion exchange membrane,AEM）电解槽将阴、阳极板间的距离缩短,大幅提高了碱性电解水器件的电流密度和效率。因此,本论文搭建了AEM电解水系统,研究了电极基底、电解液（p H值、温度、流速）以及隔膜厚度对AEM电解水性能的影响。并将Ni-Co₃O₄和Ru/α-Co（OH）₂分别作为AEM电解水器件的阳极和阴极催化剂。通过选择基底、调控催化层优化器件电极,提高器件电解水性能。对比基于商业Ru O₂和Pt/C催化剂的器件性能,基于Ni-Co₃O₄和Ru/α-Co（OH）₂的AEM器件具有更好的活性和稳定性。本章工作为开发和应用AEM电解水器件,以及实验室电催化剂在器件中的应用提供了技术途径。更多还原

【Abstract】 The energy crisis and environmental pollution problems have forced mankind to develop clean,renewable energy to replace traditional fossil energy.Electrocatalysis,in combination with new energy technologies,can convert low-value chemicals into high-value chemicals necessary for production and life,which has received a large amount of attention.Electrocatalysts and reaction devices are essential to achieve efficient electrocatalytic reactions.Among many electrocatalysts,cobalt-based electrocatalytic materials have the advantages of low cost and better electrocatalytic performance,showing broad application prospects.In addition,the reaction device affects the efficiency,activity,and stability of electrochemical reactions.Currently,the electrocatalytic performance does not meet the production needs of society.Therefore,the work designed cobalt-based electrocatalysts for hydrogen evolution reduction（HER）,oxygen evolution reduction（OER）and oxygen reduction reaction（ORR）,and revealed the structure-performance relationship.Meanwhile,new alkaline electrolytic water device was built and the laboratory catalysts were applied to the device,providing a technical way for the development of catalytic materials from laboratory to practical applications and electrolytic water devices.First,this work optimized the active sites of spinel cobalt oxide by doping strategy.Two-dimensional（2D）spinel-type Ni-doped Co₃O₄（Ni-Co₃O₄）with atomic-level thickness was prepared for OER and ORR by a hydrothermal method.Electrochemical test results show that the Ni-Co₃O₄ nanosheets exhibit bifunctional catalytic performances with the overpotential of 275 m V for OER and the onset-potential of 0.92 V for ORR.The analysis results demonstrate that the Ni doing contributes to creating the oxygen vacancies and promotes the electron transfer from nickel to cobalt ions.Eventually,the content of Co²⁺as the ORR catalytic active site and Ni³⁺as the OER catalytic active site was increased.In addition,the 2D nanostructure and Ni doping help to facilitate the charge transfer during the reaction,and in-situ Raman characterization demonstrates that the real active species of OER process is more biased towards Ni ions.This work offers a strategy for preparing highly active and durable spinel transition metal oxides materials for bifunctional oxygen catalysts.Secondly,designing composite materials is an effective strategy to regulate the electronic structure of active sites to optimize electrocatalytic performance.In the work,electrocatalytic performance of cobalt hydroxide composites are enhanced by designing active heterogeneous interfaces.The a andβ-phase cobalt hydroxide（a/β-Co（OH）₂）and loaded ruthenium composites（Ru/Co（OH）₂）are prepared by co-precipitation and chemical impregnation methods,respectively,and the prepared composites were applied to alkaline HER.Electrochemical test results show that a-Co（OH）₂@Ru has good HER performance,better than that of Ru/β-Co（OH）₂.The HER activity of Ru/α-Co（OH）₂ was comparable to that of commercial Pt/C at a current density of-10 m A cm^-2 and was significantly better than that of Pt/C at large current densities.Research demonstrates that the prepared a-Co（OH）₂nanosheets facilitate the uniform and high-density dispersion of Ru clusters,and form Ru–O–Co bonds at the interface.Density functional theory（DFT）calculations demonstrate that the longer Ru–O–Co bond in Ru/α-Co（OH）₂ optimizes the free energy barrier for water dissociation and OH^-desorption compared to Ru/β-Co（OH）₂ to facilitate the Volmer reaction step and accelerate the basic HER kinetics.This work offers new strategy for designing composite electrocatalysts for high activity.The efficiency,current density and start-stop feature of current commercial electrolytic water hydrogen production cannot meet the national demand for hydrogen energy technology development.Alkaline anion exchange membrane（AEM）electrolyzer shortens the distance between cathode and anode plates,thus significantly increasing the current density and efficiency of alkaline electrolytic water device.Therefore,this work builds an AEM water electrolysis system and investigates the effects of electrode substrate,electrolyte（p H,temperature and flow rate）and diaphragm thickness on the AEM water electrolysis performance.Moreover,Ni-Co₃O₄ and Ru/α-Co（OH）₂ was used as anode and cathode electrocatalysts for the AEM water electrolysis device,respectively.Optimize device electrodes by selecting substrates and modulating catalytic layers to improve device electrolytic water performance.Comparing the commercial Ru O₂ and Pt/C-based AEM water electrolysis performance,the Ni-Co₃O₄ and Ru/α-Co（OH）₂-based device has better activity and stability.The work provides a technical approach to the development and application of AEM electrolytic water devices,and the application of laboratory electrocatalysts in the devices.更多还原