Critical role of empty in-gap states in the photocatalytic water splitting on carbon nitride nanosheets
Critical role of empty in-gap states in the photocatalytic water splitting on carbon nitride nanosheets
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DOI：
10.1016/j.apsusc.2023.158806
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发表时间：
2023-10
影响因子：
6.7
通讯作者：
Yaru Liu;X. Zhang;Ya-nan Jiang;Min Zhang;Yuchen Ma
中科院分区：
文献类型：
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作者：
Yaru Liu;X. Zhang;Ya-nan Jiang;Min Zhang;Yuchen Ma
引入氮空位和非金属掺杂剂是提高氮化碳纳米片光催化分解水效率的一种常用策略。特别地，Nat.Energy2021，6，388-397报道了对于含有氮空位和硼掺杂剂的氮化碳纳米片，1.16%的令人着迷的太阳能到氢效率。然而，这些缺陷对反应机理的影响仍然未知。通过第一性原理计算，我们发现H_2O在理想瓜上的分裂只能在激发态下在电荷转移激子的辅助下实现，而且这种激发态反应很容易被水溶液破坏;氮空位和硼掺杂剂的关键作用应该是它们引入了空位，能使反应在基态实现或避免水溶液的负效应的间隙态。然而，硼掺杂会使三嗪间的氮空位中毒，并损害其还原性能。这两种现象不会发生在两个协调的氮空位，但H2O分裂在这个缺陷需要电荷转移激子。上述缺点可能限制了氮空位和硼掺杂对甜瓜光催化分解水的进一步改善。引入合适的空态可能是设计良好的光催化剂裂解H2O的方法。
Introducing nitrogen vacancies and non-metal dopants is one popular strategy to improve the photocatalytic H2O splitting efficiency of carbon nitride nanosheets. Especially,Nat. Energy2021,6, 388–397 reported a fascinating solar-to-hydrogen efficiency of 1.16% for the carbon nitride nanosheets containing nitrogen vacancies and boron dopants. However, effects of these defects on the reaction mechanism remain unknown. Through first-principles calculations we reveal that H2O splitting on perfect melon can only be realized in the excited state under the assistance of charge-transfer excitons, moreover this excited-state reaction is easily destroyed by aqueous solution; the key role of nitrogen vacancies and boron dopants should be that they introduce empty in-gap states which can either make the reaction realized in the ground state or avoid the negative effect of aqueous solution. However, the inter-triazine nitrogen vacancy can be poisoned and the reduction capability can be damaged by boron dopants. These two phenomena do not occur at two-coordinated nitrogen vacancies, but H2O splitting at this defect requires charge-transfer excitons. Above shortcomings may limit further improvement of melon on photocatalytic H2O splitting by doping nitrogen vacancies and boron. Introducing appropriate empty states might be the way to design good photocatalysts for splitting H2O.