【作者】 白雪；

【导师】 管景奇；

【作者基本信息】 吉林大学 ， 物理化学， 2025， 博士

【摘要】 传统化石燃料的枯竭及其引发的环境污染问题使得全球能源格局面临重大挑战。在此背景下,电化学储能器件的开发与应用对于推动能源领域的可持续发展具有重要意义。与其他储能器件相比,锌-空气电池（ZABs）具有高的理论能量密度、安全稳定和环保清洁等特点,在能源转化领域受到广泛关注。然而,ZABs阴极氧还原反应(（ORR）和析氧反应(（OER）的缓慢动力学不仅限制了高能量密度的实现,也阻碍其工作效率的进一步提升。因此开发高活性的阴极反应催化剂来加速ZABs的反应动力学是当前研究的主要方向。碳基单原子催化剂（SACs）因其高的原子利用率、明确的活性位点而被广泛研究。然而,金属原子易于团聚的特性限制了活性位点密度的提升。相较于单纯增加位点数量,提高金属中心的催化活性是更高效的策略来加速氧电催化动力学。合理设计并精确表征单原子位点的配位环境和电子结构对于理解催化机制和提升催化活性至关重要,是推动SACs从实验室研究走向实际应用的关键。作为一种在自然界中广泛存在于天然析氧物种活性中心的元素,Mn在电催化OER过程中表现出极大的潜力。此外,与单原子Fe、Co、Ni基催化剂相比,Mn基催化剂具有更低的芬顿反应活性,在ORR中表现出更高的稳定性。然而,关于Mn基电催化剂的研究仍处于起步阶段。深入探究Mn基SACs的催化性能和机制,以激发其OER/ORR双功能催化潜力,对于推动ZABs的发展具有重要意义。基于此,本课题以金属Mn原子为研究对象,合成了一系列以碳材料为基底的Mn基原子催化剂。聚焦于Mn原子的不同配位环境,深入探究周围非金属杂原子（O、S、N）配位和同核Mn-Mn相互作用对Mn中心电子结构的调控,分析这类调控对其电催化OER、ORR性能的影响,进而考察其在ZABs中的应用潜力。研究内容具体涵盖以下四个方面:（1）硫诱导的锰-氧-碳位点的电子结构调节用于电催化析氧通过简单的高温煅烧策略,在氧化石墨烯（GO）上合成了一种硫诱导的锰-氧-碳催化剂(（Mn-S₂O₂-C-500）并研究其OER活性。同步辐射(（XAS）表征揭示了催化剂中锰原子与两个硫原子和两个氧原子配位。在1 M KOH中,在电流密度为10 mA cm^-2时,Mn-S₂O₂-C-500的过电位(η₁₀)为332 m V,塔菲尔斜率为56 m V dec^-1,显示出优异的OER活性。结合理论计算,确定了Mn-S₂O₂为催化活性中心,其中*O氧化为*OOH是速率控制步骤。S和O的共配位引起Mn电荷的重新分配和优化,从而显著提高了OER活性。研究结果为设计高性能OER催化剂提供了新的思路。（2）多配位壳层调控策略提高孤立锰原子的氧还原活性在硫/氧共配位的基础上,进一步结合多配位壳层调控策略,合成了具有新的Mn-O/S配位构型的SAC（Mn-S₁O₄-C-600）,使其具有优异的ORR活性。XAS结果表明,Mn-S₁O₄-C-600中锰原子与四个氧原子和一个硫原子结合,且氧原子和硫原子分别处于第一层和第二层壳层。在0.1 M KOH中,Mn-S₁O₄-C-600表现出优异的ORR性能,其半波电位(E_1/2)为0.86 V,在0.6 V时的动力学电流密度（J_k）为10.3 mA cm^-2。由于不含N配位,该催化剂具有良好的抗芬顿性能,且基于Mn-S₁O₄-C-600的ZAB具有1.46 V的开路电压和出色的循环稳定性,优于Pt/C。理论计算表明,多配位壳层的引入增加了Mn中心的电荷密度,降低了能垒。这一结果不仅为ORR催化剂的设计提供了新的思路,也为后续研究中进一步优化催化剂性能提供了理论支持。（3）吡啶氮与硫的协同作用提高锰位点的双功能氧活性为了进一步增强金属-载体相互作用,引入高温来缩短金属与配位原子的配位距离。以硫脲为N/S源来调控Mn位点上的N和S的比例,合成了具有Mn-N₂S₂位点的OER/ORR双功能催化剂（Mn-N₂S₂-C）。实验结果表明,Mn-N₂S₂-C的OER和ORR的电位间隙（ΔE）为0.6 V(E_1/2=0.91 V,η₁₀=280 m V)。以Mn-N₂S₂-C为阴极催化剂制备的ZABs的最大功率密度达到193 m W cm^-2,且输出稳定性良好。理论计算揭示了双功能OER/ORR活性位点为嵌入石墨烯框架中的Mn-N₂S₂部分（Mn-N₂S₂G）。S原子的配位和结构的不对称性导致ortho-Mn-N₂S₂G的OER/ORR活性高于其他配位结构（如Mn-N₄G、Mn-N₃SG、para-Mn-N₂S₂G和Mn-N₃S₃G）。（4）Mn-Mn双原子位点的构建及其氧还原性能研究针对单原子稳定性不足,异核双原子活性归属不明确的问题,构建了Mn-Mn双原子位点。提出了双碳层模板策略,合成了同核Mn基DAC(（Mn₂-DC-S）。高角度环形暗场扫描透射电子显微镜（HAADF-STEM）显示,双原子Mn间的平均距离为2.81?。在碱性条件下,该催化剂表现出优异的ORR性能,其在0.6 V时的J_l和J_k分别为5.45 mA cm^-2和35.2 mA cm^-2。Mn₂-DC-S基ZABs的比容量达到了814 mAh g _Zn^-1,且在800 h的充放电循环中,充放电电压差仅增大0.05V。XAS和理论计算表明,ORR过程中,Mn的化合价先升高后降低,归因于锰位点上氧中间体的吸附和Mn-N/S配位键的伸缩。此外,第二个Mn原子的引入使得金属中心的溶解电位升高,增强了活性位点的稳定性。更多还原

【Abstract】 The depletion of traditional fossil fuels and the environmental pollution problems have posed a significant challenge to the global energy landscape.Against this backdrop,the development and application of electrochemical energy storage devices are of critical importance for advancing sustainable development in the energy sector.Compared with other energy storage devices,zinc-air batteries（ZABs）have high theoretical energy density,and are safe,stable,and environmentally friendly,thus receiving extensive attention in the field of energy conversion.However,the sluggish kinetics of the oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）at the cathode of ZABs not only limit the realization of high energy density but also hinder further enhancement of their operational efficiency.Therefore,the development of highly active cathode reaction catalysts to accelerate the reaction kinetics of ZABs is the main direction of current research.Carbon-based single-atom-catalysts（SACs）have been widely studied because of their high atomic utilization and specific active sites.However,the characteristic that metal atoms are prone to agglomeration limits the increase in the density of active sites.Compared with simply increasing the number of sites,enhancing the catalytic activity of the metal center is a more efficient strategy to accelerate oxygen electrocatalysis kinetics.Rational design and precise characterization of the coordination environment and electronic structure of single-atom sites are crucial for understanding the catalytic mechanism and enhancing the catalytic activity,and are the keys to promoting the transformation of SACs from laboratory research to practical application.As an element widely present in the active centers of natural oxygen-evolving species,Mn has great potential in the electrocatalytic OER.In addition,compared with Fe,Co,and Ni-based catalysts,Mn-based catalysts have lower Fenton reaction activity and higher stability in ORR.However,the research on Mn-based electrocatalysts remains in its infancy.In-depth exploration of the catalytic performance and mechanism of Mn-based SACs to stimulate their OER/ORR dual-functional catalytic potential is of great significance for the development of ZABs.Based on this,the research focuses on the metal Mn atoms as the object of study,and has successfully prepared Mn-based SACs with carbon materials as the substrate.Focusing on the diverse coordination environments of Mn atoms,this study investigates in depth the modulation of the electronic structure of Mn centers by surrounding non-metal heteroatoms（O,S,N）coordination and homonuclear Mn-Mn interactions.The impact of such modulation on their electrocatalytic performance in OER and ORR is systematically analyzed,and their potential applications in ZABs are further evaluated.The research content specifically covers the following four aspects:（1）Sulfur-induced electronic structure regulation of manganese-oxygen-carbon sites for electrocatalytic oxygen evolutionA sulfur-induced manganese-oxygen-carbon catalyst（Mn-S₂O₂-C-500）was synthesized on graphene oxide（GO）via a simple high-temperature calcination strategy,and its OER activity was studied.X-ray absorption spectroscopy（XAS）characterization revealed that Mn in the catalyst was coordinated with two sulfur atoms and two oxygen atoms.In 1 M KOH,Mn-S₂O₂-C-500 demonstrated excellent OER activity,with an overpotential(η₁₀)of 332 m V at a current density of 10 mA cm^-2,and the Tafel slope was 56 m V dec^-1.Combined with theoretical calculations,the Mn-S₂O₂was identified to be the catalytic active center,where the oxidation of*O to*OOH was the rate-determining step.The co-coordination of S and O induces the charge redistribution and optimization around the Mn center,significantly enhancing OER activity.These findings provide novel insights for designing high-performance OER catalysts.（2）Improving the oxygen reduction activity of isolated manganese atoms through a multi-coordination shell strategyBased on the co-coordination of sulfur/oxygen and further combined with the multi-coordination shell regulation strategy,a SAC（Mn-S₁O₄-C-600）with a novel Mn-O/S coordination configuration was synthesized,endowing it excellent ORR activity.XAS results indicated that in Mn-S₁O₄-C-600,one Mn atom was bonded to four O atoms and one S atom across two different coordination shells.In 0.1 M KOH,Mn-S₁O₄-C-600 exhibited excellent ORR performance with a half-wave potential(E_1/2)of0.86 V and a kinetic current density（J_k）of 10.3 mA cm^-2 at 0.6 V.Due to the absence of N coordination,the catalyst has good anti-Fenton performance,and the Mn-S₁O₄-C-600-based ZABs demonstrated an open circuit voltage of 1.46 V and excellent cycling stability,outperforming commercial Pt/C.Theoretical calculations revealed that the addition of atoms in the second coordination shell increased the charge density of Mn centers and reduced the energy barriers.This result not only provides new insights in the design of ORR catalysts but also offers theoretical support for further optimizing catalyst performance in subsequent studies.（3）The synergistic action of pyridine nitrogen and sulfur increases the bifunctional oxygen activity of manganese atomsTo further enhance the metal-support interaction,high temperature is introduced to shorten the coordination distance between the metal and coordinating atoms.Utilizing thiourea as the N/S source to regulate the N/S ratio at the Mn sites,and a bifunctional OER/ORR catalyst（Mn-N₂S₂-C）with Mn-N₂S₂ sites was synthesized.The Mn-N₂S₂-C demonstrated a minimal potential gap（ΔE=0.6 V）between OER(E_1/2=0.91 V)and ORR(η₁₀=280 m V).The ZAB employing Mn-N₂S₂-C as cathode catalyst achieved a maximum power density of 193 m W cm^-2 and excellent operational stability.Experimental characterization and theoretical calculations revealed that the bifunctional OER/ORR active site was the Mn-N₂S₂ part（Mn-N₂S₂G）embedded in the graphene framework.The doping of S atoms and structural asymmetry endowed ortho-Mn-N₂S₂G better OER/ORR activity than other coordination structures（such as Mn-N₄G,Mn-N₃SG,para-Mn-N₂S₂G,and Mn-N₃S₃G）.（4）Construction of Mn-Mn dual-atom sites for electrocatalytic oxygen reductionTo address the insufficient stability of SACs and ambiguous activity attribution in heteronuclear dual-atom systems,Mn-Mn dual-atom sites were constructed.A dual-carbon-layer templating strategy was developed to synthesize homonuclear Mn-based DACs（Mn₂-DC-S）.High-angle annular dark-field scanning transmission electron microscope（HAADF-STEM）image revealed an average Mn-Mn interatomic distance of 2.81?.Under alkaline conditions,the catalyst demonstrated exceptional ORR performance with a limiting current density（J_l）of 5.45 mA cm^-2 and kinetic current density（J_K）of 35.2 mA cm^-2 at 0.6 V.Mn₂-DC-S-based ZAB achieved a specific capacity of 814 mAh g _Zn^-1,while exhibiting minimal voltage gap increase（0.05 V）during the 800-h charge-discharge cycles.XAS and theoretical calculations revealed that the valence of Mn increases first and then decreases during ORR,which was attributed to the adsorption of oxygen intermediate on Mn sites and the expansion of Mn-N/S coordination bonds.Notably,the introduction of a second Mn atom elevated the dissolution potential of the metal center and enhanced the stability of the active site.更多还原