具有π-π共轭超分子结构的g-C3N4光催化新体系构建及其全解水制氢性能研究

It is an ideal way to realize the generation of hydrogen from one-step photocatalytic overall water splitting. However, the disordered migration and low transfer efficiency of photogenerated charge carriers have extremely restricted the improvement of photocatalytic overall water splitting activity. In view of this, the applicant proposes through supramolecular self-assembly method to construct novel π-π conjugated g-C3N4 photocatalytic system, while the π-π conjugated structures are easily controlled by means of non-metallic element doping, the creation of π-π conjugated isotype heterojunctions and the creation of π-π conjugated heterogeneous heterojunctions by the dual cocatalysts introduction. As a result, the driven force of charge carriers separation can be greatly promoted, leading to the enhancement of the spatially directional separation and transfer process of photogenerated charges, as well as the improvement of photocatalytic overall water splitting performance for g-C3N4. Besides, the influence mechanism of supramolecular self-assembly reaction conditions on π-π conjugated structure and micromorphology of g-C3N4 supramolecular assembly will be explored by means of the systematic preparation, characterization and activity evaluation. Moreover, the synergistic strengthening rules between π-π conjugated structure and different reinforcing methods, as well as the dynamics mechanism of photocatalytic overall water splitting reaction will be revealed by the investigation of the spatial separation process for photogenerated charges. We expect to provide a new idea and practice basis for the construction of novel π-π conjugated photocatalyst for overall water splitting.

太阳能光催化全解水一步制氢制氧技术是实现氢气绿色高效生产的理想途径。然而，由于传统光催化剂存在载流子无序化迁移及传质效率低的问题，大大限制了全解水制氢活性的提高。鉴于此，本项目拟采用超分子自组装技术构建基于π-π共轭强化的g-C3N4光催化剂，同时利用非金属元素掺杂、同相异质结和双助剂强化等手段，对π-π共轭结构形成的内建电场电势差进行调控，提升分离驱动力，从而强化载流子在空间尺度上的定向分离与有序化传递，大大提高光催化全解水制氢活性。通过系统制备、表征和活性评测分析研究，揭示超分子自组装反应条件对π-π共轭分子结构和g-C3N4超分子组装体微观形貌的影响机制。通过对光生载流子有序化传递路径的探索研究，揭示π-π共轭结构与上述不同强化手段对载流子空间定向分离与传递的协同强化规律，阐明光催化全解水产氢与产氧动力学机理，为具有π-π共轭分子结构的高效全解水光催化剂开发提供新的思路和实践基础。

中国共产党第十九次全国代表大会报告指出：加快生态文明体制改革，建设美丽中国的重要举措首先是推进绿色发展，壮大节能环保产业、清洁生产产业、清洁能源产业。氢能作为一种清洁、安全、高效的能量载体，实现其高效的开发与利用契合生态文明建设的主题，契合新时代主题。太阳能光催化全解水一步制氢制氧技术是实现氢气绿色高效生产的理想途径。鉴于此，本项目提出采用超分子自组装技术构建基于π-π共轭强化的g-C3N4光催化剂，同时利用构建同相异质结、特定微观结构和双助剂强化等手段，对π-π共轭结构中内建电场的电势差和催化剂微观形貌进行调控，强化载流子在空间尺度上的定向分离与有序化传递，增强催化剂表面对水分子的吸附，从而显著地提高光催化全解水制氢反应活性。基于上述思路，本项目首先合成了具有局部π电子离域程度可调的π-π共轭g-C3N4同相异质结光催化剂，通过增强π-π共轭效应调控材料内部静电势，促使其产氢活性提高至94.94μmol h-1。此外，分别构建了具有三维有序密堆积结构纳米球阵列和空心囊泡状的g-C3N4光催化剂，阐明了其特殊的微观结构对水分子吸附和富集、光生载流子分离的强化机制。在此基础上，分别构建了CoP/CoO双助剂负载的π-π共轭g-C3N4和具有内外表面双助剂分离的增强π-π共轭g-C3N4空心球光催化剂，实现了g-C3N4光催化剂全解水活性的突破。通过系统表征和活性评测分析研究，揭示了超分子自组装反应条件对具有增强π-π共轭结构g-C3N4光催化剂电子结构和微观形貌的影响机制。通过对光生载流子有序化传递的实验测试和理论计算，揭示了π-π共轭结构中载流子空间定向分离与传递的协同强化规律，阐明了光催化全解水产氢产氧动力学机理，为设计和开发具有π-π共轭超分子结构的高效全解水光催化剂提供了新思路和实践借鉴。