期刊
JOURNAL OF PHYSICAL CHEMISTRY A
卷 121, 期 25, 页码 4754-4764出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpca.7b04594
关键词
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资金
- Munich Centre for Advanced Photonics
- International Max Planck Research School of Advanced Photon Science (IMPRS-APS)
- Alexander von Humboldt Research Award
Impressive progress has recently been achieved in photocatalytic hydrogen evolution with polymeric carbon nitride materials consisting of heptazine building blocks. However, the fundamental mechanistic principles of the catalytic cycle are as yet poorly understood. Here, we provide first-principles computational evidence that water splitting with heptazine-based materials can be understood as a molecular excited-state reaction taking place in hydrogen-bonded heptazinewater complexes. The oxidation of water occurs homolytically via an electron/proton transfer from water to heptazine, resulting in ground-state heptazinyl and OH radicals. It is shown that the excess hydrogen atom of the heptazinyl radical can be photodetached by a second photon, which regenerates the heptazine molecule. Alternatively to the photodetachment reaction, two heptazinyl radicals can recombine in a dark reaction to form H-2, thereby regenerating two heptazine molecules. The proposed molecular photochemical reaction scheme within hydrogen-bonded chromophorewater complexes is complementary to the traditional paradigm of photocatalytic water splitting, which assumes the separation of electrons and holes over substantial time scales and distances.
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