石墨相氮化碳结构与界面的调制及提高光解水制氢活性和稳定性研究

Graphitic carbon nitride (g-C3N4), as visible light active photocatalyst, has attracted intensive research interests, because of the excellent characteristics for photocatalysis, such as environmental friendly, abundant and rich building elements and chemical stability. However, the low degree of crystallinity and poor electron transfer of g-C3N4 result in poor activity for photocatalytic water-splitting to hydrogen. And, the H2O2 generated from water oxidation that adsorbed on the surface of g-C3N4 induces deactivation. Towards these challenges, we attempt to employ the strategies of adjusting the crystallinity and specific surface area of g-C3N4 and depositing hydrogen evolution catalysts (HEC) and oxygen evolution catalysts (OEC) as dual active sites to enhance the separation of photogenerated electrons and holes, to gain the catalytic activity for water oxidation to oxygen through 4e process and to increase the photocatalytic activity and stability for water-splitting to hydrogen. In this proposal，we will investigate the key pyrolysis reaction conditions to obtain condensed g-C3N4 with high degree of cystallinity, and the preparation methods to acquire porous nanostructured g-C3N4. And, we should elucidate the effects of cystallinity and specific surface area on the properties of electron transfer, light absorption, photoluminescence and photocurrent. Finally, we need to study the methods to deposit the HEC and OEC on porous nanostructured g-C3N4 and the influences of the dual active sites on photocurrent, overpotential, water oxidation to oxygen and photocatalytic activity and stability. Through these investigations, we aim to obtain an efficient and stable photocatalytic water-splitting system by constructing the HEC and OEC co-loaded porous g-C3N4 nanostructres with high cystallinity and surface area.

石墨相氮化碳(g-C3N4)具有环境友好、组成元素含量丰富和化学稳定等特点，成为可见光活性光催化材料研究的重点。但结晶度不高和电子传递能力差导致其光解水制氢活性低，表面催化水氧化产生吸附态过氧化氢导致其失活。针对以上两个科学问题，本项目拟采用提高结晶性和比表面积及界面负载析氢和析氧双催化活性位点的策略来促进光生电子和空穴分离，增加界面水氧化4e途径和氧气析出速率及提高光解水制氢的活性和稳定性。研究热解过程中提高g-C3N4聚合程度和结晶度的关键制备因素及高比表面积多孔纳米结构的制备方法；研究结晶性和比表面积对电子传递、光吸收、光致发光和光电流的影响；研究界面析氢和析氧双活性催化位点对光电流、过电势、水氧化产物及光解水产氢活性和稳定性的影响。从而获得高结晶度、大比表面积和界面析氢和析氧活性位点双负载的g-C3N4多孔纳米结构光解水制氢体系。

本项目聚焦氮化碳本征结构和界面电子与缺陷调控对氮化碳光物理、光催化和光解水分解过程影响的关键科学问题，研究(1) 氮化碳微结构与形貌的调控，包含C/N配比对光电响应、导电性与二维超薄结构的影响，二维褶皱与空洞形貌对光催化分解水活性影响，孔结构与比表面积对光催化分解水活性；(2) 氮化碳界面电子与缺陷的调控，包含表面缺陷结构的制备，界面杂多酸簇组装对光催化活性的影响；(3) 微结构、形貌、缺陷和聚集态（相）对光物理和光催化的影响，包含光吸收与荧光、激发态寿命与动力学、界面电子传递、带隙与导带/价带氧化还原电势、光电流与IPCE，光生电子和空穴对表面吸附物的氧化还原。获得了（1）前驱体中引入小分子葡萄糖实现调控碳氮元素组成和层数及类石墨烯氮化碳（Graphene-like carbon nitride）新材料；（2）氮化碳缺陷表面组装杂多酸簇活性位点构筑高活性超分子杂化光催化材料；（3）氮化碳褶皱形貌调控及对光解水制氢活性的影响；（4）氮化碳空洞形貌及对光解水制氢循环稳定性的影响；（5）氮化碳中混合相结构对光解水制氢活性的影响。通过本项目研究对发展氮化碳新材料，氮化碳结构基元、电子结构和聚集态认知，氮化碳新型催化应用等具有重要的学术价值。