TY - JOUR
T1 - Mechanism of Photocatalytic Water Splitting with Graphitic Carbon Nitride
T2 - Photochemistry of the Heptazine-Water Complex
AU - Ehrmaier, Johannes
AU - Karsili, Tolga N.V.
AU - Sobolewski, Andrzej L.
AU - Domcke, Wolfgang
N1 - Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/6/29
Y1 - 2017/6/29
N2 - 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 heptazine-water 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 H2, thereby regenerating two heptazine molecules. The proposed molecular photochemical reaction scheme within hydrogen-bonded chromophore-water 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.
AB - 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 heptazine-water 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 H2, thereby regenerating two heptazine molecules. The proposed molecular photochemical reaction scheme within hydrogen-bonded chromophore-water 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.
UR - http://www.scopus.com/inward/record.url?scp=85022192847&partnerID=8YFLogxK
U2 - 10.1021/acs.jpca.7b04594
DO - 10.1021/acs.jpca.7b04594
M3 - Article
C2 - 28592110
AN - SCOPUS:85022192847
SN - 1089-5639
VL - 121
SP - 4754
EP - 4764
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 25
ER -