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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Efficient Photocatalytic Hydrogen Evolution on Band Structure Tuned Polytriazine/Heptazine Based Carbon Nitride Heterojunctions with Ordered Needle-like Morphology Achieved by an In Situ Molten Salt Method
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Efficient Photocatalytic Hydrogen Evolution on Band Structure Tuned Polytriazine/Heptazine Based Carbon Nitride Heterojunctions with Ordered Needle-like Morphology Achieved by an In Situ Molten Salt Method

机译：高效的光催化氢气进化在带结构调谐聚集锌/七氮化碳氮化物异质结，其通过原位熔融盐法实现了有序针状形态

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Polymeric carbon nitride (CN) is a fascinating metal-free photocatalyst for active solar energy conversion via water splitting. However, the photocatalytic activity of CN is significantly restricted by the intrinsic draWbacks of fast charge recombination because of incomplete polymerization. Herein, an in situ ionothermal molten salt strategy has been developed to construct polytriaine/heptazine based CN isotype heterojunctions from low cost and earth-abundant urea as the single-source precursor, with the purpose of greatly promoting the charge transfer and separation. The engineering of crystallinity and phase structure of CN has been attempted through facile tailoring of the conderthation conditions in a molten salt medium. Increasing the synthetic temperature and eutectic salts/urea molar ratio leads to the formation of CN from bulk heptazine phase to crystalline polytriazine imide (P11) phase, while CN isotype heterojunctions are in situ created at moderate synthetic temperature and salt amount. As evidenced by the measurements of UV-vis DRS and Mott-Schottky plots, the conduction band potentials can be tuned in a wide range from -1.51 to -0.96 V by controlling the synthetic temperature and salt amount, and the apparent band gap energies are reduced accordingly. The difference in band positions between PTI and heptazine phase CN enables the formation of CN heterojunctions, greatly promoting the separation of charge carriers. These metal-free CN heterojunctions demonstrate a well ordered needle-like morphology, and the optimal sample yields a remarkable hydrogen evolution rate (4813.2 mu mol g(-1)), improved by a factor of 12 over that of bulk heptazine-based CN and a factor of 4 over that of PTI. The enhanced photocatalytic performance can be directly ascribed to the synergistic effect of the improved crystallinity with reduced structural defects, the decreased band gap energy with tunable band positions, and the efficient separation of charge carriers induced by the formation of heterostructures.
机译：聚合物碳氮化物（CN）是一种迷人的无金属光催化剂，用于通过水分裂的活性太阳能转换。然而，由于不完全聚合，CN的光催化活性被快速电荷重组的内在缺点显着限制。在此，已经开发了一种原位离子熔融盐策略，用于将来自低成本和土坯尿素的Cn同种型异质结构成为单源前体，目的是大大促进电荷转移和分离。 CN的结晶度和相结构的工程通过熔融盐介质中的阴囊化条件的容纳剪裁而试图。增加合成温度和共晶盐/脲摩尔比率导致将Cn的形成从批量七嗪相到结晶的聚集嗪酰亚胺（P11）相，而CN同种型异质结原位以中等的合成温度和盐量产生。如通过UV-VIS DRS和MOTT-SCHOTTKY图的测量所证明，通过控制合成温度和盐量，传导电位可以在-1.51至-0.96V的宽范围内调谐，并且表观带隙能量是相应减少。 PTI和七肽相位CN之间的带状位置的差异使得能够形成CN异质结，极大地促进电荷载体的分离。这些无金属CN异质型证明了一种有序的针状形态，最佳样品产生显着的氢进化速率（4813.2μmmolg（-1）），在批量基于甲庚嗪的CN中提高了12倍。和PTI的一个超过4。增强的光催化性能可以直接归因于改进的结晶度的协同效应，具有降低的结构缺陷，具有可调谐带位置的减小的带隙能量，以及通过形成异质结构诱导的电荷载体的有效分离。

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