【作者】 刘扬；

【导师】 张翼；

【作者基本信息】 中南大学 ， 分析化学， 2023， 硕士

【摘要】 在碳达峰,碳中和的发展目标下,电解水和金属-空气电池等技术因其绿色环保和转化效率高等优点受到了广泛关注,但这些技术严重依赖高效稳定的电催化剂,因此开发经济、稳定、高活性的电催化剂已成为近年来新型能源转化技术的研究热点。单原子催化剂是负载型催化剂的极限状态,其中,双金属单原子催化剂因其具有易调节的电子结构和催化活性而备受关注。本论文采用了简单的水凝胶模板法,制备了一系列具有优异电催化活性的原子级分散铁基双金属碳气凝胶材料。具体研究内容如下:（1）本研究使用明胶水凝胶为前驱体,以纳米Si O₂作为造孔剂,金属（Fe、Ni）络合物作为金属源和氮源,经过低温热解、碱洗等处理后得到原子分散的双金属掺杂碳气凝胶。BET测试表明碳气凝胶具有丰富的孔径结构,比表面积达到了467.7 m²g^-1。电化学测试结果显示NCA/Fe Ni-500双金属单原子催化剂在碱性介质（1.0 M KOH）中具有最佳的OER催化活性,其在10 m A cm^-2电流密度下的过电位仅为288 m V,Tafel斜率为61.2 m V dec^-1,优于商用Ru O₂催化剂(361m V,93.4 m V dec^-1)。将NCA/Fe Ni-500作为阳极催化剂用于电解水,在碱性介质（1.0 M KOH）和模拟碱性海水（0.5 M Na Cl+1.0 M KOH）中达到10 m A cm^-2电流密度所需的电压分别仅为1.556 V和1.546 V,且均能保持100 h以上的稳定性。DFT理论计算表明,NCA/Fe Ni-500中邻位Ni-N₄位点对Fe-N₄位点的电荷转移调控作用降低了Fe-N₄位点上O-O键生成能能垒,从而提升了Fe-N₄位点的OER活性。本工作为研究双金属单原子电催化剂的活性调控机制提供了新的思路。（2）以明胶水凝胶为前驱体,通过控制热解法得到了Fe、Ru双金属掺杂的碳气凝胶（NCA/FeRu）。双球差矫正的透射电镜以及高分辨XPS光谱显示Fe、Ru双金属均以原子分散的形式分布于氮掺杂碳骨架中。电化学测试结果表明NCA/FeRu具备优异的ORR、OER、HER三功能活性。在碱性介质中NCA/FeRu催化ORR反应的半波电位高达+0.92 V,同时催化OER和HER达到10 m A cm^-2所需的过电位分别仅为283 m V和8 m V,其催化活性在这三种反应中均优于传统贵金属催化剂。使用NCA/FeRu作为阴极催化剂组装的柔性锌-空气电池的开路电压可达1.49 V,最大功率密度达138.2 m W cm^-2,并且能够在连续1000次充放电循环过程中保持性能稳定,展现出了良好的应用前景。本研究结果说明双金属单原子催化剂在多功能催化方面具有较大的优势。图45幅,表11个,参考文献103篇更多还原

【Abstract】 For facing the development goal of carbon peaking and carbon neutrality,electrochemical water splitting and metal-air batteries have attracted much attention for their environmental friendliness and high conversion efficiency.However,the performance of these technology is heavily dependent on efficient and stable electrocatalysts.Therefore,the development of low-cast,stable and high-performance electrocatalysts has been the focus of research in the field of new energy conversion technologies.Single-atom catalysts are the limit state of loaded catalysts,among which bimetallic single-atom catalysts are of interest due to their tunable electronic structures and catalytic activities.In this paper,a series of Fe-based dual-atom carbon aerogels with remarkable catalytic ability are synthesized by a simple hydrogel template method.The details of the study are as follows:（1）In this study,we use gelatin hydrogel as precursors,nano-Si O₂ as the pore-forming agent,metal（Fe,Ni）complexes as the metal and nitrogen sources,after low-temperature pyrolysis and alkali etching,we prepare a series of atomically dispersed bimetal-doped carbon aerogels.BET tests show that carbon aerogel has abundant pore structure with a specific surface area of up to 467.7 m² g^-1.The electrochemical tests show that the NCA/Fe Ni-500 has the best OER catalytic activity in alkaline medium（1.0M KOH）,with an overpotential of 288 m V at a current density of 10 m A cm^-2 and a Tafel slope of 61.2 m V dec^-1,which is superior to commercial Ru O₂ catalyst(361 m V,93.4 m V dec^-1).Using NCA/Fe Ni-500 as an anode catalyst for water splitting,the voltage required to achieve 10 m A cm^-2 in alkaline medium（1.0 M KOH）and simulated alkaline seawater（0.5 M Na Cl+1.0 M KOH）is only 1.556 V and 1.546 V,respectively,and both can maintain stability for more than 100 hours.DFT theoretical calculation indicates that the charge transfer modulated effect of adjacent Ni-N₄ sites on Fe-N₄ sites in NCA/Fe Ni-500 reduced the energy barrier of O-O bond on Fe-N₄ sites.This work provides a new approach for studying the activity regulation mechanism of bimetallic single atom electrocatalysts.（2）Fe、Ru doped carbon aerogel（NCA/FeRu）were obtained by controlled pyrolysis using gelatin gel as precursor.AC-HAADF-STEM and HR-XPS indicate that both Fe and Ru are atomically dispersed in nitrogen doped carbon aerogel.The electrochemical tests show that NCA/FeRu has excellent ORR,OER,and HER catalytic activities.In alkaline medium,NCA/FeRu shows an impressive ORR performance with a high E_1/2 of+0.92 V,Meanwhile,the overpotential required for OER and HER to reach 10 m A cm^-2 is only 283 m V and 8 m V,respectively.Its catalytic activity in these three reactions is superior to traditional noble-metal catalysts.The flexible Zn-air battery assembled with NCA/FeRu as cathode catalyst can reach an open circuit voltage of 1.49 V,while its maximum power density reaches 138.2 m W cm^-2.Moreover,NCA/FeRu exhibits significant catalytic stability during 1000 consecutive charge and discharge cycles,demonstrated outstanding application prospects.The results of this study indicates that bimetallic single-atom catalysts have advantages in multifunctional catalysis.更多还原