【作者】 李振宇；

【导师】 张伟； 邹旭；

【作者基本信息】 吉林大学 ， 材料物理与化学， 2024， 硕士

【摘要】 与利用化石燃料制氢的传统方法相比,通过电化学驱动水分解是获得高纯氢气的理想技术路线。目前,碱性电解水（AWE）技术已经较为成熟,可用于商业化的氢气生产。与AWE技术相比,质子交换膜（PEM）电解水技术具有更大的优势,例如:更低的欧姆损耗、更紧凑的系统设计、更高的电流密度、更快的系统响应和高气体纯度等。但是在该技术中,由于阳极析氧反应（OER）过程中强酸性和强氧化条件的限制,导致大多数催化剂难以满足要求。到目前为止,只有昂贵的Ir O₂是PEM电解槽中用于酸性条件下的的商用电催化剂。与Ir O₂相比,同为金红石相结构的Ru O₂具有更好的催化活性,而且价格更加便宜,被认为是Ir O₂催化剂的潜在替代品。然而,Ru基催化剂在酸性水氧化过程中容易过度氧化为可溶性高价Ruⁿ⁺（n>4）,导致其稳定性较差,这严重阻碍了其进一步发展。因此,在调控Ru O₂催化活性同时保证其在酸性水氧化过程中的稳定性是其面临的最大挑战。本论文以金红石相氧化钌为研究对象,结合理论计算,通过阳离子掺杂和固溶体策略对其活性位点进行调控,从而优化Ru的电子结构,获得兼具高活性和高稳定性的Ru O₂基催化剂。本论文的研究内容及结果如下:1.Ca掺杂对金红石相氧化钌中Ru-O相互作用的研究。使用熔融盐法合成均为金红石相结构的Ca-Ru O₂和Ru O₂催化剂,且精细结构表征表明两者具有几乎相同Ru-Ru和Ru-O配位结构。电化学活性比表面积测试表明Ca的引入有效提高了活性位点的密度及本征活性。塔菲尔斜率和电化学阻抗也证明了Ca-Ru O₂在催化过程中具有更快反应动力学。通过理论计算发现,Ca-Ru O₂中Ru的d带中心远离费米能级,弱化了Ru位点和含氧中间体之间的相互作用,降低了Ru-O之间的COHP值。适度的Ru-O相互作用降低了催化的反应能垒,改变了原本的反应决速步,提升了催化剂的OER活性。Ca-Ru O₂在电流密度达到10mA/cm²时,过电势仅为198 m V。同时,Ca的引入还增加了Ru O₂中表面Ru的溶出能,减缓Ru位点的过氧化,提升催化剂的稳定性。在10 mA/cm²的计时电位测试中,Ca-Ru O₂可稳定100 h以上且无明显性能衰减。2.Te-O-Ru桥键对Ru位点电子结构影响的研究。除阳离子掺杂调控策略外,合成Ru基氧化物固溶体也是一种调控Ru位点电子结构和提升稳定性的有效方法。通过对不同钌碲比例的氧化物固溶体(Ru_1-XTe _XO₂)进行测试,筛选出了拥有最佳活性的Ru_0.9Te_0.1O₂,在10 mA/cm²的电流密度下过电势只有205 m V。Ru_0.9Te_0.1O₂具有最小的塔菲尔斜率和最低的阻抗,表明适量Te掺杂可促进电子转移。为研究Te-O-Ru桥键的电荷转移情况,构建了Ru_0.875Te_0.125O₂固溶体模型,理论计算结果表明具有较低电负性的Te引起了电子向Ru位点转移,使Ru处于更低的氧化态。Ru位点的富电子状态使费米能级附近的d电子数增加,使得更多的电荷可参加反应,降低了决速步能垒,加快反应动力学。而且,Ru_0.9Te_0.1O₂中晶格氧p带下移,减缓了Ru位点的过氧化,提升了酸性水氧化过程中的稳定性。在计时电位测试中,Ru_0.9Te_0.1O₂可在10 mA/cm²的电流密度下稳定80 h以上。更多还原

【Abstract】 Compared with traditional hydrogen production methods using fossil fuels,electrochemically driven water splitting is an ideal technical route to obtain high-purity hydrogen.At present,alkaline water electrolysis（AWE）is relatively mature and can be used for commercial hydrogen production.Compared with alkaline water electrolysis,proton exchange membrane（PEM）water electrolysis has great advantages,such as lower ohmic loss,more compact system design,higher current density,faster system response and high gas purity.However,due to the limitations of strong acidity and strong oxidation conditions in the oxygen evolution reaction（OER）,it is difficult for most of the available catalysts to meet the requirements.So far,only Ir O₂ is a commercial electrocatalyst used in PEM electrolyzer.Ru O₂,which has the same crystal structure as Ir O₂,is considered a potential alternative to Ir O₂ due to its better catalytic activity and cheaper price.However,ruthenium-based catalysts are easy to be over-oxidized to soluble high valence Ruⁿ⁺（n>4）during acid water oxidation,which leads to their poor stability and seriously hinders their further development.Therefore,the biggest challenge is to regulate the catalytic activity of Ru O₂ while ensuring its stability during acidic water oxidation.In this thesis,rutile ruthenium oxide was taken as the research object,combined with theoretical calculation,and its active sites were regulated by cation doping and solid solution strategies,so as to optimize the electronic structure of Ru and obtain Ru O₂-based catalysts with high activity and high stability.The research contents and results of this paper are as follows:1.Effect of Ca doping on Ru-O interaction in rutile ruthenium oxide.Ca-Ru O₂and Ru O₂ catalysts,both with rutile phase structures,were synthesized using the molten salt method,and the fine structure characterization indicates that they have almost the same Ru-Ru and Ru-O coordination structure.Electrochemically active specific surface area tests showed that the introduction of Ca effectively increased the density of active sites and intrinsic activity.The Tafel slope and electrochemical impedance indicate that Ca-Ru O₂ has faster reaction kinetics in the catalytic process.Theoretical calculation proves that the d-band center of Ru in Ca-Ru O₂ is far away from the Fermi level,which weakens the interaction between the Ru sites and the oxygen-containing intermediate,and reduces the COHP value between Ru-O.The moderate Ru-O interaction reduces the reaction energy barrier of the electrocatalysis,changes the rate-determining step,and increases the OER activity of the catalyst.When the current density of Ca-Ru O₂reaches 10 mA/cm²,the overpotential is only 198 m V.On the other hand,the introduction of Ca also increases the dissolution energy of surface Ru in Ru O₂,which slows down the peroxidation of Ru sites and improves the OER stability of the catalyst.In the chronopotentiometric test of 10 mA/cm²,Ca-Ru O₂ can be stable for more than100 h without any obvious performance degradation.2.Effect of Te-O-Ru bridge bond on the electronic structure of Ru sites.In addition to the cationic doping modulation strategy,the synthesis of the Ru-based oxide solid solution is also an effective method to regulate the electronic structure and improve the stability of Ru sites.Through the performance tests of oxide solid solution(Te _XRu_1-XO₂)with different ruthenium-tellurium ratios,Ru_0.9Te_0.1O₂ was selected for the best activity,and the overpotential was only 205 m V at 10 mA/cm².Ru_0.9Te_0.1O₂ has the smallest Tafel slope and the lowest impedance,indicating that an appropriate amount of Te doping can promote the dynamics of OER and accelerate electron transfer.In order to study the charge transfer of the Te-O-Ru bridge bond,a model of Ru_0.875Te_0.125O₂ solid solution was constructed.Theoretical calculations show that Te with lower electronegativity causes an electron transfer to the Ru sites,which leads to a lower oxidation state of Ru.The electron-rich state of the Ru site increases the number of d electrons near the Fermi level,promotes more charges participating in the reaction,reduces the rate-determining step energy barrier and accelerates the reaction kinetics.Moreover,the downward shift of the lattice oxygen p-band in Ru_0.9Te_0.1O₂slows down the peroxidation of the Ru sites and enhances the stability during acidic water oxidation.In the chronopotentiometric test,Ru_0.9Te_0.1O₂ can be stable for more than 80 h at 10mA/cm².更多还原