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

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。

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.