Subject Number : S-16-NM-0067
Support Type : 機器利用
Proposal Title (English) : Development of new visible light active photocatalysts
Username (English) : Guigao Liu
Affiliation (English) :Hokkaido University, Frontier Biomaterials Science

1. Summary
In this research, a p-n homojunction structured carbon nitride photocatalyst were prepared, which was a result of the introduction of cyano electron-accepting group into the material. Such p-n homojunction structure endowed the as-prepared photocatalyst with increase light absorption and improved electron transfer efficiency, consequently resulting in the much enhanced activity for water splitting. The detailed structure of the photocatalyst was investigated by solution NMR.

2. Experimental
NMR experiments were performed under ambient condition on a JEOL ECS-400 NMR spectrometer.
Before the measurement, the powder samples were dissolved in the concentrated H2SO4 solution.

3. Results and Discussion
Graphitic carbon nitride (g-C3N4) has recently emerged as an attractive photocatalyst for solar energy conversion. However, the photocatalytic activities of g-C3N4 remain moderate because of the insufficient solar-light absorption and the fast electron–hole recombination. Here, defect-modified g-C3N4 (DCN) photocatalysts, which are easily prepared under mild conditions and show much extended light absorption with band gaps decreased from 2.75 to 2.00 eV, are reported. More importantly, cyano terminal CΞN groups, acting as electron acceptors, are introduced into the DCN sheet edge, which endows the DCN with both n- and p-type conductivities, consequently giving rise to the generation of p–n homojunctions. This homojunction structure is demonstrated to be highly efficient in charge transfer and separation, and results in a fivefold enhanced photocatalytic H2 evolution activity. The findings deepen the understanding on the defect-related issues of g-C3N4–based materials. Additionally, the ability to build homojunction structures by the defect-induced self-functionalization presents a promising strategy to realize precise band engineering of g-C3N4 and related polymer semiconductors for more efficient solar energy conversion applications.

4. Others
This work received financial support from the National Basic Research Program of China (973 Program, 2014CB239301), the World Premier International Research Center Initiative (WPI Initiative) on Materials Nanoarchitectonics (MANA), MEXT, Japan, the JSPS KAKENHI (Grant No. 15F15070) and the Mitsubishi Foundation.
Platform staff assisted me on NMR user training.
5. Publication/Presentation
(1) Liu, G.; Zhao, G.; Zhou, W.; Liu, Y.; Pang, H.; Zhang, H.; Hao, D.; Meng, X.; Li, P.; Kako, T.; Ye, J., In Situ Bond Modulation of Graphitic Carbon Nitride to Construct p–n Homojunctions for Enhanced Photocatalytic Hydrogen Production. Adv. Funct. Mater. 2016, 26 (37), 6822-6829.

6. Patent
N/A