能源短缺和环境污染是未来制约人类社会发展的最主要的问题之一。而探索和开发新型清洁可再生能源是解决未来能源和环境问题，进而推动人类社会发展的关键。太阳能作为一种取之不尽、用之不竭的新型能源，是解决未来能源短缺和环境污染问题的最具潜力的新型清洁能源之一。光催化技术能够将太阳能转化为化学能与电能，从而实现太阳能的转化与存储，是有效利用太阳能来解决能源与环境问题最具潜力的技术手段之一。而目前光催化的效率较低，成为制约其实际应用的最主要问题。因此，探索新型高效光催化材料，进一步提高光催化的能量转换效率，对推动光催化技术进步，进而解决未来能源和环境问题具有重要的意义。 在众多光催化材料中，氮基半导体材料因其具有良好的可见光吸收、合适的能带结构、较高的稳定性和良好的半导体性能，是一类极具发展潜力的光催化材料，因而受到人们的广泛关注。然而，受氮基材料制备技术限制，目前对氮基半导体材料的组分、缺陷、形貌等参数尚不能很好的调控，而这些参数对氮基半导体材料本身的光吸收、载流子分离和电子结构均具有重要影响，是制约氮基材料光催化活性的关键问题之一。因此，本论文选择几种具有前景的氮基材料，如： TaON、Ta₃N₅、Nb₄N₅、g-C₃N₄等，作为研究对象，针对这些材料制备过程和实际应用中的一些关键问题，从材料结构与性能的关系入手，通过研究氮基材料的生长过程与制备技术，实现对氮基材料组分、形貌、缺陷的精确调控，从而进一步拓展氮基材料的光吸收范围和促进光生载流子分离，进而提高其光催化活性，为设计制备新型高效氮基光催化材料提供新的方法和理论依据。在此基础上，结合材料本身的特性，结合光电化学、超级电容器等，开展了一些光电化学分解水和氮基超级电容器等方面的探索研究工作。 在第一章中，首先对太阳能转化储存为化学能与电能的主要方式以及基本原理进行了基本介绍，然后对常见的材料体系的研究现状，以及基本优缺点进行了总结概括，并重点对极具潜力的氮化物材料体系进行了较为详细的介绍，并对解决当前材料性能缺陷的基本方法进行了简单概括，最后提出了本论文的选题意义和主要研究内容。 在第二章中，针对传统高温氮化法难以制备合成取向性氮化物材料的问题，开发了一种新的CCl₄辅助高温氮化法。以LiTaO₃单晶为衬底剥离制备了[100]取向的TaON薄膜及以KTaO₃单晶为衬底剥离制备了[153]取向的Ta₃N₅薄膜，该方法可以以相应的单晶为衬底，在CCl₄辅助下，通过内延生长制备具有高取向性的自支撑薄膜，解决了传统氨气高温氮化法无法制备高取向钽基氮化物的问题。通过该种方法制备的薄膜除了具备晶体结构的取向性以外，还具有独特的由颗粒连接而成的垂直于薄膜表面的准一维棒状结构。基于对单晶衬底与产物的晶体结构分析以及相应的实验结果，提出了该方法取向性生长TaON自支撑薄膜的基本原理：首先前驱体LiTaO₃与产物TaON在特定取向上具有相似的原子排布结构，这使转化过程中的应力得到极大的降低，从而得到相应的取向性结构，而在制备过程中通过加入CCl₄，LiTaO₃前驱体中的杂质元素Li可以以LiCl的形式在高温条件下以气体的形式挥发去除，并且部分钽元素以氯化物的形式去除从而留下足够的空间进行后续氮化反应。当反应结束，降温过程中，LiCl的凝固，会使界面处相应的应力得到释放，从而导致TaON以薄膜的形态完整的剥离下来。通过研究CCl₄辅助高温氮化法制备取向性TaON薄膜的生长机理，为下一步利用该方法制备其他材料提供了基本的理论基础，以此为基础，有望利用此方法合成制备出其他的具有独特结构与性能的材料。 在第三章中，针对取向性TaON光电性能表现与改性问题进行了相应研究。首先研究了高取向结构TaON的光电分解水性能，研究表明，TaON晶体结构的高取向性明显提高了其光电分解水能力，其性能约为无取向的2倍。另外，我们研究发现大量氮空位缺陷的存在会抑制TaON的光电表现，通过在NH₃气氛下退火，在不破坏晶体取向性的前提下，我们成功地移除了相应的氮空位，从而使取向性TaON薄膜光电性能得到极大的增强，其光电流可以增加3.7倍，达到2.84 mA ㎝⁻²。针对TaON在光电测试过程中容易氧化形成相应的氧化物(Tao〓)而导致性能降低的问题，我们对其进行了助催化剂改性研究。首先，我们研究了CoPi在取向性TaON薄膜光电极中的作用，结果表明，虽然Co-Pi能够有效地提高TaON光电极的光电流密度，但是其不均匀负载性导致其仍然无法解决TaON电极的氧化腐蚀性问题。针对此问题，我们通过熔盐法构建了新的钴基助催化剂Co₄N，通过此方法可以实现Co₄N助催化剂在TaON颗粒周围的均匀负载，光电性能测试表明，均匀负载的Co₄N助催化剂既可以有效地提高TaON光电极的水分解能力，亦能够有效地抑制TaON电极的氧化腐蚀性问题。本工作首先证明了取向性TaON具有优异的光电性能，其次验证了新的助催化体系Co₄N在TaON材料中的有效应用。 在第四章中，针对氮化碳光利用效率低与载流子复合效率高问题，我们首先对其进行了元素掺杂改性研究，通过超分子自组装法，以壳聚糖与三聚氰胺作为前驱体成功构建了碳自掺杂的氮化碳材料。理论与实验研究表明，碳元素通过替换桥连氮而成功进入氮化碳的晶格之中，促进了大π键的形成，从而促进光生载流子的分离效率与光利用效率。另外，我们对氮化碳的氮空位缺陷结构进行了调控研究。通过在不同气氛下(H₂与CCl₄气氛)成功制备了具有不同氮空位的氮化碳材料(三嗪环氮空位以及悬挂氮空位)，研究表明两种氮空位均会在禁带中引入杂质能级，单占据态的杂质能级能够作为电子捕获位而捕获光生电子然后作为产氢位点进行光催化产氢反应。光催化性能研究表明由于悬挂氮空位相比于三嗪环氮空位具有更高的杂质电子局域态，因此含有悬挂氮空位的氮化碳表现出了更高的光催化活性。其次，我们在CCl₄气氛下构建了独特的具有1D空心四方柱结构的氮化碳材料(GCN-THP)，并研究了微观形貌对氮化碳性能的影响。经过研究提出了构建该独特形貌结构的氮化碳生长机理。研究表明，独特的1D空心纳米结构能够有效促进光的散射与吸收以及载流子的分离效率，从而能够有效提高氮化碳材料的光催化分解水性能。本章工作分别从元素掺杂，缺陷调控，形貌调控三个方面对氮化碳进行了改性研究，该工作的方法与相应结论有望为其他材料体系的改性研究提供一定指导。 在第五章中，针对常规氮化碳材料多为粉体，可循环利用性差的问题，我们开发了一种利用CCl₄原位提取成核位点从而在多种衬底上构建g-C₃N₄连续薄膜的方法。通过在不同衬底上制备的薄膜研究表明，该方法的基本原理为，在CCl₄作用下，衬底中的金属离子能够被原位提取到衬底表面，然后与g-C₃N₄分子中的富电子氮相互作用而嵌入到g-C₃N₄分子结构中，最后这些金属离子作为锚点而使g-C₃N₄分子连续生长为薄膜。该方法制备的薄膜为连续膜(非颗粒堆积膜)，因此可以脱离衬底而独立存在，并且其相关理化性质可以通过控制制备条件而进行调节。性能研究表明，该方法制备的薄膜不仅具有良好的光催化性能，同时具有良好的循环稳定性与可回收利用性。该方法具有操作简单，无需特殊工艺，成本低廉，可拓展等优点，为g-C₃N₄的循环利用以及在薄膜领域的应用提供了基础，并且该方法有望拓展应用到其他薄膜体系的构建中。 在第六章中，针对电能存储问题，我们对氮化物超级电容器材料进行了研究。通过CCl₄辅助高温氮化法以LiNbO₃单晶为前驱体，成功制备了Nb₄N₅薄膜材料。通过XPS研究发现，该样品内部与表面具有不同价态的铌原子，其内部铌原子价态较低，而表面价态较高，另外晶体结构研究发现，沿着[211]方向Nb₄N₅具有交替排布的Nb原子层与N原子层。独特的结构排布与化学组分导致了当Nb₄N₅作为电极用于储能时，电极内部的电子能够快速的传输到电极表面，从而促进质子在表面的吸附。因此虽然制备的样品具有较小的比表面积，但是其电容测试表明其仍然具有优异的电容性能，其功率与能量密度可分别达到12.5 mW ㎝⁻²与24.6μWh㎝⁻²，循环性测试表明连续循环2000圈无明显性能衰减。本工作证明了通过CCl₄辅助高温氮化法可以成功构建具有优异性能的氮化物电容电极材料，另外以晶体结构为基础，研究了晶体结构与组成成分对材料性能的影响，有望为将来研究更优异的非氧化物电容电极材料提供新的思路与方法。 总之，氮基材料作为一种极具前景的能量转化与存储材料，对能量转化与储存技术发展及其实际应用具有重要意义。在本论文中，通过研究TaON、Ta₃N₅、 Nb₄N₅、g-C₃N₄等氮基材料制备过程—微观结构—物理性能之间的关系，实现了对其微结构参数和能量转化与储存性能的调控，探索了氮基材料结构与性能之间的基本规律，这对改善和进一步提高氮基材料性能，设计和制备新型高效氮基材料，推动能量转化与储存技术发展和实际应用具有重要的意义。 关键词：取向性氮化物；氮化物光(电)催化剂；光(电)催化分解水；氮化物超级电容器

 Energy shortages and environmental pollution are among the most important issues that constrain the development of human society in the future. The exploration and development of new clean renewable energy is the key to solving future energy and environmental problems. As an inexhaustible new energy source, solar energy is one of the most promising new clean energy sources to solve future energy shortages and environmental pollution problems. Photocatalytic technology can convert solar energy into chemical energy to realize solar energy conversion and storage. It is one of the most potential technical means to effectively use solar energy to solve energy and environmental problems. At present, the efficiency of photocatalysis is still low, which has become the most important problem that restricts its practical application. Therefore, exploring new efficient photocatalytic materials and further improving the energy conversion efficiency is of great significance for promoting the progress of photocatalytic technology and solving future energy and environmental problems. Among many photocatalytic materials, nitrogen-based semiconductor materials are a kind of photocatalytic materials with great development potential because of their good visible light absorption, suitable band structure, high stability and good semiconductor performance. However, due to the limitation of the preparation technology, the composition, defects, and morphology of nitrogen-based semiconductor materials are not well regulated, and these parameters are important for light absorption and carrier separation of nitrogen-based semiconductor materials. Therefore, this paper selects several potential nitrogen-based materials as research objects, such as: TaON, Ta₃N₅, Nb₄N₅, g-C₃N₄, etc.. By studying the growth process and preparation technology of nitrogen-based materials, the precise regulation of the composition, morphology and defects of nitrogen-based materials can be realized, thereby further expanding the light absorption and promoting the separation of photogenerated carriers. Our work provides new methods and theoretical basis for the design and preparation of new high-efficiency nitrogen-based photocatalytic materials. Combining with the characteristics of the material itself and photoelectrochemistry, supercapacitors, etc., some research works on photoelectrochemical water splitting and nitrogen-based supercapacitors were carried out. In Chapter 1, the basic methods and principles of solar energy conversion and storage are firstly introduced. Then, the research status of common material systems, as well as their basic advantages and disadvantages are summarized, and the nitrides are discussed in detail. Finally, the basic methods for solving the disadvantages of current materials were briefly introduced, and then we put up the significance and main research contents of this thesis. In Chapter 2, a new CCl₄ assisted nitridation method was developed for solving the difficulty of preparing oriented nitride materials through preparation method. [100]oriented TaON films were fabricated by using LiTaO₃ single crystal as the substrates and [153]-oriented Ta₃N₅ films were also prepared by using KTaO₃ as the substrates. This method can prepare oriented free-standing films by endotaxial growth with the aid of CCl₄, which solve the problem that the conventional high temperature nitridation method cannot prepare the highly oriented tantalum-base nitrides. The film prepared by this method has a unique rod-like structure perpendicular to the surface of the film. Based on the crystal structure analysis between the single crystal substrate and TaON product and the corresponding experimental results, the basic growth mechanism of the oriented TaON free-standing film is proposed. In detail, firstly, the precursor LiTaO₃ and the product TaON have similar atomic arrangement in a specific orientation, which greatly reduces the stress during the conversion process. In the preparation process, by adding CCl₄, the impurity element Li in the LiTaO₃ precursor can be evaporated in the formation of LiCl gas under high temperature condition, and some tantalum atoms are removed in the form of chlorides, which leaves enough space for subsequent nitridation. When the reaction is completed, the solidification of LiCl causes the corresponding stress released at the interface, resulting in the complete peeling of TaON film. By studying the growth mechanism of oriented TaON thin films prepared by CCl₄ assisted nitridation method, it provides a basic theoretical basis for the further preparation of other materials by this method. Based on the results, it is expected to use this method to synthesize and prepare other materials with unique structures and performance. In Chapter 3, the performance of the oriented TaON and its modification were studied. Firstly, we studied the photoelectrochemical water splitting properties of the high oriented TaON. The results show that the high oriented crystal structure of TaON significantly improves its photoelctrochemical water splitting performance, which is about twice that of non-oriented TaON. In addition, we found that the presence of nitrogen vacancy defects inhibits the photoelectrochemical performance of TaON. By annealing under NH3 atmosphere, the nitrogen vacancies were successfully removed without destroying the oriented structure. Then the photoelectrochemical performance of the TaON film was greatly enhanced, its photocurrent can be increased by 3.7 times to 2.84 mA ㎝⁻². In order to solve the problems that TaON is easily oxidized to form corresponding oxides (TaO〓) during the photoelectrochemical test, we carried out researches on the modification of the TaON with cocatalyst. Firstly, we studied the role of Co-Pi in the oriented TaON photoelectrode. The results show that although Co-Pi cocatalyst can effectively improve the photocurrent density of TaON photoelectrode, its uneven distribution makes it still cannot solve the stability problem of TaON clectrode. Aiming at this problem, we constructed a new cobalt-based cocatalyst C04N by molten salt method. The uniform load of CO₄N cocatalyst around TaON particles can be achieved by this method. The photoelectrochemical performance test shows that the uniformly covered C04N cocatalyst not only can effectively increase the performance of the TaON photoelectrode but also can effectively suppress the oxidative corrosion of the TaON electrode. This work firstly proved the excellent photoelectrochemical properties of oriented TaON, and then verified the effective application of the new cocatalyst system C04N in TaON material system. In Chapter 4, in view of the problem that the low light utilization and the high carrier recombination efficiency of carbon nitride, we first carried out the element doping research, using supramolecular self-assembly method with chitosan and melamine as the precursor, we constructed a supramolecular structure, and the carbon self-doped carbon nitride material was successfully constructed with subsequent calcination process. Theoretical and experimental studies show that carbon elements successfully enter the crystal lattice of carbon nitride by replacing bridging nitrogen atoms, which promotes the formation of big π bonds, so that photogenerated electrons can efficiently transfer between adjacent heptazines. Then the separation efficiency of photogenerated carriers and light utilization efficiency are improved. This work proves that the element doping of carbon nitride can be achieved by supramolecular self-assembly method, which provides a new idea and way for the preparation of high-performance, low-cost carbon nitride with element doping. In addition, we systematically studied the nitrogen vacancy defects of carbon nitride. The carbon nitride materials with different nitrogen vacancies (ring nitrogen vacancies and pendent nitrogen vacancies) were prepared under different atmospheres (H₂ and CCl₄ atmospheres). Based on experimental and theoretical calculation studies, both nitrogen vacancies can introduce defect levels into the band gaps, and the single occupied defect level can serve as electron trapping site to capture photogenerated electron and then as the hydrogen generation sites. In addition, the nitrogen vacancies can provide additional transfer channels for electrons, thereby increasing the separation efficiency of photogencrated carriers. Photocatalytic performance studies show that carbon nitrides with pendent nitrogen vacancies show higher photocatalytic activity due to the higher electron localization compared to ring nitrogen vacancies. This work provides detailed theoretical and experimental evidence for understanding the photocatalytic mechanism of carbon nitride with nitrogen vacancy defects, which is helpful for the synthesis of highly efficient carbon nitride materials. Moreover, we constructed carbon nitride material (GCN-THP) with a unique 1D hollow prism structure under CCl₄ atmosphere, and then studied the effect of microstructure on carbon nitride performance. The growth mechanism of carbon nitride with hollow prism was constructed by studying the related morphologies and surface states during different preparation processes. The method realizes a simple, low-cost and safe preparation process for fabricating 1D hollow carbon nitride structure by using low-polymerization melamine as the template. Studies show that the unique 1D hollow nanostructure can effectively promote the light scattering and absorption as well as the carrier separation efficiency, thus effectively improve the photocatalytic water splitting performance of carbon nitride materials. This work provides a new method for constructing carbon nitride materials with unique nanostructure, which is expected to be extended to other material systems. In Chapter 5, the problems that conventional carbon nitride is usually in powder form and has poor recyclability are considered, thus we developed a method to construct g-C₃N₄Continuous films on a variety of substrates by using CCl₄. Studies on the thin films prepared on different substrates show that the basic principle of the method is that under the action of CCl₄, the metal ions in the substrates can be extracted in situ to the surface of the substrates, then with the reaction between electron-rich nitrogen atoms in g-C₃N₄ and the metal cations, metal cations can be embedded into the molecular structure of g-C₃N₄. Finally, these metal ions act as anchor points to continuously grow g-C₃N₄ molecules into thin films. The film prepared by this method is a continuous film (non-particle interaction film), and thus can exist independently from the substrate. Moreover, the film’s physical and chemical properties can be easily adjusted by controlling the preparation conditions. Performance studies show that the film prepared by this method not only has good photocatalytic performance, but also has good cycle stability and recyclability. The method has the advantages of simple operation, no special process, low cost and expandability, and provides a possibility for the reuse of g-C₃N₄ and the application in the field of thin films, and the method is expected to be extended to the construction of other thin film systems. In Chapter 6, we studied nitride supercapacitor materials for electrical storage problems after solar energy is converted into electrical energy. The Nb₄N₅ material was successfully prepared by the CCl₄ assisted nitridation method using LiNbO₃ single crystal as the precursor. It is found by XPS that the niobium atoms have different valence states at the interior and the out surface of the sample, where the interior niobium atoms have lower valence states while the niobium atoms on the out surface have higher surface valence states. In addition, crystal structure studies find that Nb₄N₅ has alternating Nb atomic layer and the N atomic layer along the [211] direction. The unique structural arrangement and chemical composition result in the electrons inside the electrode rapidly transporting to the electrode surface when Nb₄N₅ is used as an electrode for energy storage, thereby promoting the adsorption of protons on the surface. Therefore, although the prepared sample has a small specific surface area, its supercapacitor test shows that it still has excellent supercapacitor performance, where its power and energy density can reach 12.5 mW ㎝⁻² and 24.6 μWh ㎝⁻², respectively, and the cyclic test shows that there was no significant performance degradation after 2000 cycles. This work proves that the nitride capacitor electrode material with excellent performance can be constructed by CCl₄ assisted nitridation method. Based on the crystal structure, the influence of crystal structure and composition on the material properties is studied. It is expected to provide new ideas and methods for developing excellent non-oxide capacitor electrode material in the future. In short, the structure and properties of materials have close relationship. In this study, different structures are prepared by different preparation methods and the relations between them are systematically studied. The studies on the relationships between material structure and properties and the growth mechanism of the construction method is of great value and significance for the future construction of efficient solar energy conversion and storage materials. Keywords: oriented nitrides; nitride photo(electro)catalyst; photo(electro)catalytic water splitting; nitride supercapacitor