【作者】 马宁；

【导师】 刘恩佐； 张海昌；

【作者基本信息】 天津大学 ， 工程（专业学位）， 2022， 硕士

【摘要】 电解水反应是一种可以将可再生能源转化为氢能的有效途径,但是该反应中阳极析氧反应（OER）的高过电位和反应势垒,以及目前商用贵金属催化剂的高成本阻碍了电解水技术的进一步发展和应用。因而,亟需开发高效率且低成本的OER电催化剂。钴基氧化物因其优异的电化学性能和稳定性成为最有前途的催化剂之一,引入氧空位和掺杂是目前改善钴基氧化物本征活性的重要手段。以此为背景,本文以钴基氧化物为研究对象,研究了氧空位影响氧化钴（CoO）的OER电催化性能的微观机制。考虑到金属氧化物在碱性电解液中易被氧化为羟基氧化物,研究了（Fe、Ni）共掺杂对羟基氧化钴（CoOOH）的OER电化学性能的影响。利用第一性原理计算研究了CoO（111）表面重构及其对氧空位（V_O）形成和OER性能的影响。在CoO（111）表面发现了CoO₆八面体到CoO₄四面体的表面重构,这提高了CoO（111）表面的OER活性和V_O的稳定性。V_O的引入改变了Co原子周围的电荷聚集状态和Co-O的键合状态,从而影响了中间体的吸附和脱附过程。通过对电子结构的分析,揭示了由于表面重构和V_O的引入导致Co位点活性变化的本质。结合实验与第一性原理计算,研究了（Fe、Ni）共掺杂对CoOOH的OER性能的影响机理。通过电沉积与阳极氧化的方法,在碳纤维布上制备出了（Fe、Ni）共掺杂的CoOOH纳米片。制得的催化剂在247 m V的低过电位下可达到10m A cm^-2的电流密度,且100 h后具有良好的稳定性。发现掺杂Fe和Ni后,催化剂的反应动力学有所增强。在热力学上,Fe掺杂使活性位点由Co变为Fe,吸附羟基步骤的吉布斯自由能变化减小。然而,羟基的强烈吸附使得下一步的脱质子反应变得困难。Ni掺杂有利于Fe和反应中间体之间的电子转移,并通过增强Fe-O共价成分进一步平衡这两个步骤。研究结果为钴基OER电催化剂的合理设计及应用提供了理论支持。更多还原

【Abstract】 Electrolytic water reaction is an effective way to convert renewable energy into hydrogen energy.However,the high overpotential and reaction barrier of anodic oxygen evolution reaction（OER）,as well as the high cost of commercial precious metal catalysts,hinder the further development and application of water electrolysis technology.Therefore,it is necessary to develop efficient and low-cost OER electrocatalysts.Cobalt oxide is one of the most promising catalysts due to its excellent electrochemical performance and stability.Introducing oxygen vacancy and doping are important methods to improve the intrinsic activity of cobalt oxides.Based on this background,this paper took cobalt oxides as the research object.The micro mechanism of the oxygen vacancy（V_O）effect on the OER electrocatalytic performance of cobalt oxide（CoO）was studied.Considering that metal oxides are easily oxidized to hydroxyl oxides in alkaline electrolyte,the effect of（Fe,Co）co-doping on the OER electrochemical performance of cobalt oxyhydroxide（CoOOH）was further studied.The surface reconstruction and its effect on the V_Oformation and OER performance of CoO（111）surface were studied using the first principles calculations.The surface reconstruction from the CoO₆octahedrons to the CoO₄tetrahedrons was revealed at CoO（111）surface,which enhanced the OER activity and the stability of V_Oat the surface of CoO（111）.The existence of V_Ochanged the electron accumulation around the Co atoms and the bonding state between Co and O atoms,and thus,affected the adsorption of hydroxyl group and deprotonation process.By analyzing the electron structure,the nature of the activity changed at Co sites due to the surface reconstruction and the introduction of V_Owas revealed.The underlying mechanism of Fe Ni-codoping effect on the OER performance of CoOOH was studied by both experiments and first principles calculations.The Fe Ni-codoped CoOOH as oxygen evolution reaction（OER）electrocatalyst was prepared successfully by simple electrodeposition and anodic oxidation methods,which exhibited a 247 m V low overpotential at 10 m A cm^-2and good stability after100 h.It was revealed that the reaction kinetics increased after doping Fe and Ni.Thermodynamically,Fe-doping changed the active site from Co to Fe and the Gibbs free energy change of adsorbing hydroxyl group decreased.However,the strong adsorption of the hydroxyl group made the next deprotonation step difficult.Ni doping benefited the electron transfer between Fe and intermediates and further balanced the two steps by enhancing the Fe-O covalent components.The results provided a theoretical basis for the rational design and application of Co-based OER catalysts.更多还原