Reactive oxygen species (ROS) are key oxidants for the degradation of organic pollutants in sunlight-driven photocatalytic water treatment, but their interaction with the photocatalyst is easily ignored and, hence, is comparatively poorly understood. Here we show that graphitic carbon nitride (C₃N₄, a famous visible-light-responsive photocatalyst) is chemically stable toward ozone and superoxide radical; in contrast, hydroxyl radical (^•OH) can tear the heptazine unit directly from C₃N₄ to form cyameluric acid and further release nitrates into the aqueous environment. The ratios of released nitrogen from nanosheet-structured C₃N₄ and bulk C₃N₄ that finally exists in the form of NO₃^– reach 9.5 and 6.8 mol % in initially ultrapure water, respectively, after 10 h treatment by solar photocatalytic ozonation, which can rapidly generate abundant ^•OH to attack C₃N₄. On a positive note, in the presence of organic pollutants which compete against C₃N₄ for ^•OH, the C₃N₄ decomposition has been completely or partially blocked; therefore, the stability of C₃N₄ under practical working conditions has been obviously preserved. This work supplements the missing knowledge of the chemical instability of C₃N₄ toward ^•OH and calls for attention to the potential deactivation and secondary pollution of catalysts in ^•OH-involved water treatment processes.

中文翻译：

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在阳光驱动的水处理中，C ₃ N _4对化学活性氧是否稳定？

活性氧（ROS）是在阳光驱动的光催化水处理过程中降解有机污染物的关键氧化剂，但是它们与光催化剂的相互作用很容易被忽略，因此对它的理解相对较差。在这里，我们显示了石墨碳氮化物（C ₃ N ₄，一种著名的可见光响应型光催化剂）对臭氧和超氧自由基的化学稳定性。相反，羟自由基（^• OH）可以直接从C ₃ N ₄撕开庚嗪单元，形成环戊二酸，并进一步将硝酸盐释放到水性环境中。纳米片结构的C ₃ N ₄和本体C ₃释放的氮的比率Ñ ₄终于存在NO的形式₃ ^-达到9.5和6.8％（摩尔）在最初的超纯水，分别由后光催化太阳能臭氧化10小时处理，其可以快速地产生丰富^• OH攻击ç ₃ Ñ ₄。在积极的，在这种竞争向C的有机污染物的存在₃ Ñ ₄为^• OH中，C ₃ Ñ ₄分解已被完全或部分封端; 因此，C ₃ N ₄的稳定性在实际的工作条件下得到了明显的保留。这项工作补充了对C ₃ N ₄对^• OH的化学不稳定性的认识，并呼吁关注^•涉及OH的水处理过程中催化剂的潜在失活和二次污染。