Abstract Photocatalytic nitrogen fixation is considered as a promising candidate for artificial green NH3 production. Searching an environment-friendly photocatalyst with high activity is necessary for the development of photocatalytic nitrogen fixation. Here, a metal-free semi-crystalline g-C3N4 with midgap states (CNV-550) was prepared by heating melamine in a sealed environment. The CNV-550 presented a photocatalytic nitrogen fixation rate of 91.6 μmol L−1 h−1 under visible light without any sacrificial reagent, which was 14.8 times as high as that of pristine g-C3N4. The midgap states from the interaction between g-C3N4 and melem extended the light response range of CNV-550 to 700 nm. The recombination of photogenerated electron-hole pairs was inhibited by the midgap states and the order-disorder interfaces of the semi-crystalline g-C3N4; accordingly, the apparent quantum efficiency reached 1.89% at 420 nm. This work not only present a metal-free high efficient photocatalyst for nitrogen fixation, but also introduces a new method to modify g-C3N4 material by controlling the reaction pressure.

中文翻译：

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具有中带隙态的半结晶石墨氮化碳，用于高效光催化固氮

摘要 光催化固氮被认为是一种很有前景的人工绿色氨生产候选方法。寻找一种具有高活性的环境友好型光催化剂对于光催化固氮的发展是必要的。在这里，通过在密封环境中加热三聚氰胺制备了具有中带隙状态的无金属半结晶 g-C3N4 (CNV-550)。CNV-550在没有任何牺牲试剂的情况下在可见光下表现出91.6 μmol L-1 h-1的光催化固氮率，是原始g-C3N4的14.8倍。g-C3N4 和 melem 之间相互作用的中能隙状态将 CNV-550 的光响应范围扩展到 700 nm。半晶态g-C3N4的中能隙态和有序-无序界面抑制了光生电子-空穴对的复合；因此，在 420 nm 处的表观量子效率达到 1.89%。这项工作不仅提出了一种用于固氮的无金属高效光催化剂，而且还介绍了一种通过控制反应压力来改性 g-C3N4 材料的新方法。