磷酸铁基材料是一类组成和结构非常丰富的无机功能材料，在储能、催化等领域有着重要的应用潜力。本论文以实现不同组成和结构的磷酸铁基材料的可控制备及应用发展为研究目标，围绕制备磷酸铁基材料的复杂沉淀体系沉淀形成和演变的基本规律以及磷酸铁基材料组成和结构的调控机制两个关键科学问题展开研究工作，在理论认识、技术创新和新材料开发方面取得的创新性成果如下。（1）确认了三价铁盐和磷酸盐反应的主要副产物及其产生与抑制条件，提出了表观离子成分为Fe3+和HPO42-是快速沉淀制备高纯FePO4的必要条件，发现了Fe2(HPO4)3在高温热处理条件下向FePO4转化的动态过程，明确了反应体系在水热环境中存在的四种磷酸铁物相并揭示了它们的热力学稳定性和相互转化的路径与条件。（2）针对高纯无定型FePO4纳米颗粒，发展了基于微反应器技术和连续直接沉淀过程的高效制备方法，发展了微反应器与高温老化耦合的技术平台，拓宽了高纯无定型FePO4纳米颗粒的制备区间，提出了利用混合酸调控离子分布的新方法，实现了9-59nm范围内的尺寸调节。针对具有纳米结构的磷酸铁基晶体材料，提出了利用固相溶解和液相络合两种在水热条件下控制晶体生长的机制，以及利用微反应器进行成核与生长解耦和独立调控的机制，成功制备了碱式磷酸铁枝晶、具有片状分级结构的磷酸氢铁晶体和多种形貌的单斜磷酸铁晶体材料。（3）揭示了碱式磷酸铁枝晶作为非均相Fenton催化剂，可以在pH值3-8的范围内都表现出良好的活性和优异的稳定性。揭示了具有片状分级结构的磷酸氢铁晶体作为一种在重复使用的便捷性和可靠性方面具有明显优势的过氧化氢仿生酶的潜力，检测双氧水的检测限可低至1μM，10次独立检测的相对标准偏差小于2%。发展了利用界面相互作用来促进无定型纳米FePO4与导电剂CNT相互分散与有效复合的新方法，作为锂离子电池正极材料时，得到的高度分散的FePO4-CNT纳米复合材料的电子传递阻力降低了4倍，表观锂离子扩散速率提升了5.5倍，5C循环2000次容量可以保持90%，倍率性能和循环稳定性明显优于文献报道结果。
Iron phosphate materials draw many attentions since they have diverse structures, compositions and high chemical reactivity, and show great potentials for applications in the fields of energy storage systems and catalysis. For iron phosphate materials, the application performance is closely depended on the composition or structure. And the development of their applications needs to make breakthrough in the controllable synthesis. To this end, we carry out fundamental researches on two key scientific issues: one is the generation and evolution mechanism of iron phosphate nanoparticles, the other is the regulation law of the composition and structure of nano-structured iron phosphate crystalline materials. Some achievements have been made in terms of theoretical recognition, technological innovation and new materials developments. They mainly include: (1) The main by-products and their formation and inhibition conditions in fast precipitation process between ferric salts and phosphate salts have been determined. The prerequisite for obtaining high-purity FePO4 is confirmed. Fe3+ and HPO42- are regarded as apparent reactive ions. The conversion from Fe2(HPO4)3 to FePO4 is observed after high-temperature aging. During hydrothermal synthesis process, four kinds of iron phosphate compounds are identified, and the relative stability in thermodynamics and the conversion routes among them are also revealed. (2) A novel method based on microreactor technology and continuous precipitation process has been developed to prepare pure FePO4 nanoparticles with high throughput. A new strategy coupling microreaction technology and high temperature aging is proposed to endow the preparation of pure FePO4 nanoparticles with operational robustness. The adjustment on the particle size from 9 nm to 59 nm is achieved through using mixed H3PO4 and HNO3 to regulate the distribution of reactive ions. Three general principles have been proposed to regulate the structure of iron phosphate crystals, which are based on the conversion of iron phosphate compounds in solid, the complexation effect between iron and phosphate ions in solution, decoupling the nucleation and growth process of iron phosphate compounds by using combinational reaction system, respectively. And then, dendritic iron hydroxyl phosphate, hierarchical iron hydrogen phosphate and monoclinic iron phosphate with various morphologies are successfully prepared. (3) Dendritic iron hydroxyl phosphate is developed as a novel Fenton catalyst for the degradation of phenol, exhibiting good catalytic activity and great stability as the pH of the reaction system is varied from 3 to 8. Hierarchical iron hydrogen phosphate crystal is firstly demonstrated to possess peroxidase-like activity and be suitable for quantitative detection of H2O2 with a low detection limit of 1 μM. Benefited from the chemical stability of the hierarchical crystal, it also has advantages in good reproducibility (relative standard deviation less than 2% for 10 independent measurements), long-term stability (no activity loss after 10 cycles), and ease of recovery (by simple centrifugation). A new strategy to generate a uniformly dispersed amorphous FePO4 and conductive CNT nano-composite is developed, which exploits the interface interaction between surface-modified amorphous FePO4 and CNT dispersion under mild sonication. The uniformly dispersed nano-composite, used as the cathode for lithium-ion battery, can significantly reduce the electron transfer resistance by 4 times and increase the apparent lithium ion diffusion coefficient by 5.5 times. Nearly 90 % of the initial discharge capacity could be retained at 5 C after 2000 cycles. The rate performance and long-term stability are very superior compared to previously reported results.
