【作者】 陶冶；

【导师】 刘波；

【作者基本信息】 中国科学技术大学 ， 无机化学， 2025， 硕士

【摘要】 近些年,对化石能源的过渡依赖及温室气体的大量排放,导致资源枯竭和全球变暖。在追求碳中和的背景下,寻找一种可再生且可持续的清洁能源成为当务之急。氢气作为一种绿色能源载体,不仅能量密度高,而且燃烧后只生成水,已成为全球研究热点。然而,氢气的易燃易爆特性使其运输和储存困难,限制了其应用。甲醇分解制氢是一种很有前景的反应,能够实现氢气的高效生产并将其输送到可以利用的地方以实现现场制氢。金属铜因其有助于断裂C–H键,在催化甲醇分解制氢中有着显著优势。但是受限于塔曼温度,铜基催化剂在高温甲醇分解制氢过程中易发生烧结而失活。开发优化铜基催化剂以提高甲醇分解制氢活性和稳定性,是一项关键挑战。基于高熵氧化物（HEOs）的高构型熵以及多组分之间的协同作用构建甲醇分解催化剂,可通过引入稳定HEOs结构的元素以及脱氢反应活性位点,从而有效提升甲醇分解制氢性能。本论文通过逐级添加金属元素,构建了从中熵到高熵的高活性甲醇分解催化剂。我们通过系统的材料设计、光电化学测试以及原位观测表征,对光驱动条件下甲醇分解机理以及光生热载流子作用机制进行了深入研究。本文主要内容概括如下:1.通过PVP模板法制备了一系列含有不同种类阳离子的中熵氧化物催化剂,并测试其太阳能驱动甲醇分解制氢反应的性能,确定四元中熵氧化物（Cr Co Ni Cu）₃O₄具备最高的催化活性。当光照强度为2.68 W cm^-2时,（Cr Co Ni Cu）₃O₄的产氢速率为32.8 mmol g^-1 min^-1,该性能是Cu/Al₂O₃产氢速率的3.5倍。光电化学测试表明,（Cr Co Ni Cu）₃O₄催化剂具有较高的光生载流子分离效率以及光吸收能力,因而其光热转化效率最高。2.在五种四元中熵氧化物的基础上,通过PVP模板法制备五元高熵氧化物（Fe Cr Co Ni Cu）₃O₄,并探究其光驱动甲醇分解制氢性能。得益于高熵材料中各个组分的协同作用,2D HEOs在模拟太阳光照射下表现出优异的光热转化活性,可将甲醇分解转化为氢气(49.4 mmol g^-1 min^-1),其速率显著高于同温度黑暗条件下的2D HEOs的表现。并且显著高于已报道的先进催化剂。通过原位除碳技术,催化剂在80 h的反应过程中表现出长期稳定性。此外,通过准原位DRIFTS研究,揭示了光热甲醇分解的反应机制及光驱动条件下光生热载流子的作用。高熵材料提供了一条新途径,能同时实现催化稳定性和活性,有利于甲醇分解实现高效制氢。更多还原

【Abstract】 In recent years,the excessive dependence on fossil energy and the massive emission of greenhouse gases have led to resource depletion and global warming.Against the backdrop of pursuing carbon neutrality,the development of a renewable and sustainable clean energy source has become an urgent necessity.Hydrogen,as a green energy carrier,exhibits high energy density and generates only water upon combustion,making it a focal point of global research.However,the highly flammable and explosive nature of hydrogen poses significant challenges for its storage and transportation,thereby limiting its practical applications.Methanol decomposition for hydrogen production is a promising reaction that enables the efficient generation of hydrogen and facilitates its on-site utilization.Copper,due to its ability to promote C–H bond cleavage,demonstrates notable advantages in catalyzing methanol decomposition for hydrogen production.However,constrained by the Tammann temperature,copper-based catalysts are prone to sintering and deactivation at elevated temperatures during the methanol decomposition process.Developing and optimizing copper-based catalysts to enhance the activity and stability of methanol decomposition for hydrogen production remains a critical challenge.The construction of methanol decomposition catalysts based on high-entropy oxides（HEOs）leverages their high configurational entropy and the synergistic interactions among multiple components.By introducing elements that stabilize the HEOs structure and serve as active sites for the dehydrogenation reaction,the catalytic performance in methanol decomposition for hydrogen production can be significantly improved.In this study,a series of highly active methanol decomposition catalysts were developed by stepwise incorporation of metal elements,transitioning from medium-entropy to high-entropy compositions.Through systematic material design,photoelectrochemical testing,and in situ characterization,we conducted an in-depth investigation into the methanol decomposition mechanism under light-driven conditions,as well as the role of photogenerated hot carriers.The main contents of this study are summarized as follows:1.A series of medium-entropy oxide（MEO）catalysts containing different cation species were synthesized via the PVP-templated method,and their performance in solar-driven methanol decomposition for hydrogen production was evaluated.It was determined that the quaternary MEO（Cr Co Ni Cu）₃O₄ exhibited the highest catalytic activity.Under a light intensity of 2.68 W cm^-2,the hydrogen production rate of（Cr Co Ni Cu）₃O₄ reached 32.8 mmol g^-1 min^-1,which is 3.5 times higher than that of Cu/Al₂O₃.Photoelectrochemical measurements revealed that（Cr Co Ni Cu）₃O₄possesses a high efficiency in photogenerated charge carrier separation and superior light absorption capability,leading to the highest photothermal conversion efficiency.2.Building upon five quaternary medium-entropy oxides,a pentanary high-entropy oxide（HEO）,（Fe Cr Co Ni Cu）₃O₄,was synthesized via the PVP-templated method,and its performance in solar-driven methanol decomposition for hydrogen production was investigated.Benefiting from the synergistic effects among multiple components in high-entropy materials,the 2D HEOs exhibited exceptional photothermal conversion activity under simulated solar irradiation,enabling the decomposition of methanol into hydrogen at a rate of 49.4 mmol g^-1min^-1.This performance was significantly higher than that of 2D HEOs under identical thermal conditions in the dark and notably superior to previously reported advanced catalysts.Furthermore,through in situ carbon removal techniques,the catalyst demonstrated long-term stability over an 80-hour reaction period.Quasi-in situ diffuse reflectance infrared Fourier transform spectroscopy（DRIFTS）studies revealed the reaction mechanism of solar-driven methanol decomposition and elucidated the role of photogenerated hot carriers under solar-driven conditions.The high-entropy material presents a new strategy for simultaneously achieving catalytic stability and activity,facilitating the efficient hydrogen production from methanol decomposition.更多还原