Abstract The high-temperature secondary calcination (>500 °C) of bulk g-C3N4 usually suffers from a very low yield of g-C3N4 nanosheets owing to its serious and massive depolymerization. In this study, a NH4Cl-induced low-temperature second-calcination approach has been used to synthesize nitrogen-rich g-C3N4 nanosheets with a high yield (ca. 32 wt%), which includes the initial intercalation of NH4Cl into the interlayers of bulk g-C3N4 and the following direct low-temperature calcination at 400 °C. It is found that during the calcination process, the thermal gas flow (HCl and NH3) from NH4Cl decomposition not only can efficiently facilitate the delamination and depolymerization of the g-C3N4 structure, but also can introduce many amino groups on the g-C3N4 surface, resulting in the successful synthesis of nitrogen-rich g-C3N4 nanosheets at such a low temperature. Experimental data suggests that the resulting nitrogen-rich g-C3N4 nanosheets show a distinct enhancement for the H2-evolution performance mainly owing to the introduction of amino groups, which can efficiently enrich H+ from water to facilitate the rapid generation of H2. This study may open up a fire-new insight for the preparation of high-efficiency nanometer materials.

中文翻译：

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NH4Cl 诱导低温形成富氮 g-C3N4 纳米片并改善光催化析氢

摘要 块状 g-C3N4 的高温二次煅烧 (>500 °C) 由于其严重和大量的解聚，通常会导致 g-C3N4 纳米片的产率非常低。在这项研究中，NH4Cl 诱导的低温二次煅烧方法已被用于合成富氮 g-C3N4 纳米片，产率高（约 32 wt%），其中包括将 NH4Cl 初始嵌入到块状 g-C3N4 和随后在 400 °C 下直接低温煅烧。发现在煅烧过程中，NH4Cl分解产生的热气流（HCl和NH3）不仅可以有效促进g-C3N4结构的分层和解聚，而且可以在g-C3N4表面引入许多氨基, 导致在如此低的温度下成功合成了富含氮的 g-C3N4 纳米片。实验数据表明，所得富氮 g-C3N4 纳米片显着提高了 H2 的析出性能，这主要是由于氨基的引入，可以有效地从水中富集 H+，促进 H2 的快速生成。这项研究可能为制备高效纳米材料开辟了一个全新的视角。