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| In this work, first-principle methods are employed to build thermodynamic models for both the pure and sulfur atom modified g-C3N4 photocatalysts. Three possible mechanisms of oxygen evolution reaction (OER) following four one-electron pathway were investigated. The hydroxyl species as a key intermediate is found to strongly interact with the catalyst, which is distinct from the previous observation. The most likely pathway is via H2O → OH → O → OOH → O2, in which the first removal of proton, the rate-determining step, can not become surmountable at room temperature until an overpotential of 0.88 V (2.11 V vs SHE) is presented, in accord with the experimental observation that water photooxidaton is difficult to occur without any modification. On the other hand, the sulfur doping significantly reduces the overpotential , consistent with the experimental finding that the water oxidation reaction could be achieved at a moderate rate with sulfur-modified g-C3N4. Our theoretical results provide useful insights for designing better visible-light-driven anode to achieve high OER activity on graphitic carbon nitride based photocatalysts. |
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| Keywords:water photooxidation; graphitic carbon nitride; reaction mechanism; thermodynamics; DFT-D; sulfur doping |
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