Journal
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
Volume 5, Issue 3, Pages 2224-2236Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acssuschemeng.6b02490
Keywords
Photocatalytic hydrogen evolution; NiS co-catalysts; g-C3N4; Trifunctional nanocarbons; Graphene
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Funding
- National Natural Science Foundation of China [51672089]
- industry and research collaborative innovation major projects of Guangzhou [201508020098]
- State Key Laboratory of Advanced Technology for Material Synthesis and Processing (Wuhan University of Technology) [2015-KF-7]
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In this work, robust nanocarbons, including graphite (G), carbon nanotube (CNT), reduced graphene oxide (rGO), carbon black (CB), and acetylene black (AB), have been successfully coupled into the interfaces between g-C3N4 and NiS using a facile precipitation method. The results demonstrated that nanocarbons played trifunctional roles in boosting the photocatalytic H-2 evolution over g-C3N4, which can not only act as effective H-2-evolution co-catalysts but can also serve as conductive electron bridges to collect photogenerated electrons and boost the H-2-evolution kinetics over the NiS co-catalysts. More interestingly, the nanocarbons can also result in the downshift of valence band of g-C3N4, thus facilitating the fast oxidation of triethanolamine and charge-carrier separation. Particularly, in all five ternary multiheterostructured systems, the g-C3N4-0.5%CB-1.0% NiS (weight ratio) and g-C3N4-0.5%AB-1.0%NiS photocatalysts exhibited the highest H-2-evolution rates of 366.4 and 297.7 mu mol g(-1) h(-1), which are 3.17 and 2.57 times higher than that of g-C3N4-1.0%NiS, respectively. Apparently, the significantly enhanced H-2-evolution activity of multiheterostructured g-C3N4/carbon/NiS composite photocatalysts can be mainly ascribed to the trifunctional nanocarbons, which serve as the conductive electron bridges rather than the general co-catalysts. More importantly, it is revealed that the amorphous carbons with higher electrical conductivity and weaker electrocatalytic H-2-evolution activity are more suitable interfacial bridges between g-C3N4 and NiS co-catalysts for maximizing the H-2 generation. This work may give a new mechanistic insight into the development of multiheterostructured g-C3N4-based composite photocatalysts using the combination of trifunctional nanocarbon bridges and earth-abundant co-catalysts/semiconductors for various photocatalytic applications.
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