Yuelin Wang1, Thanh Ngoc Pham2, Yu Tian3, Yoshitada Morikawa4, Likai Yan5. 1. Institute of Functional Material Chemistry, Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun 130024, PR China; Department of Precision Engineering, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan. 2. Department of Precision Engineering, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan. 3. Institute of Functional Material Chemistry, Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun 130024, PR China. 4. Department of Precision Engineering, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan; Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Goryo-Ohara, Nishikyo-ku, Kyoto 615-8245, Japan; Research Center for Ultra-Precision Science and Technology, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Osaka, Japan. Electronic address: morikawa@prec.eng.osaka-u.ac.jp. 5. Institute of Functional Material Chemistry, Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun 130024, PR China. Electronic address: yanlk924@nenu.edu.cn.
Abstract
A new-type nitrogen-rich carbon nitride material C3N5 has been synthesized recently, in which the C:N ratio increases from 3:4 in g-C3N4 to 3:5 due to the introduction of azo linkage (NN) connecting segments in two C6N7 units. Herein, C3N5 as a photocatalyst for CO2 reduction was investigated by density functional theory methods. The electronic and optical properties indicate that C3N5 has a longer visible-light region with 2.0 eV of band gap in comparison with g-C3N4. The spatial distributions of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) show that the π network of C3N5 is extended by introducing -NN- linkage, which results in much higher photocatalytic efficiency than g-C3N4. The Gibbs free energies for possible CO2 reaction paths on C3N5 were computed. The results show that CO2 can be reduced to CH4 with a low limiting potential of -0.54 V and to CH3CH2OH with a low limiting potential of -0.61 V, which all driven by solar energy. The present work is expected to provide useful guide for new-type nitrogen-rich C3N5 as promising photocatalyst for CO2 reduction reaction (CO2RR).
A new-type nitrogen-rich n class="Chemical">carbon nitride material C3N5 has been synthesized recently, in which the C:N ratio increases from 3:4 in g-C3N4 to 3:5 due to the introduction of azo linkage (NN) connecting segments in two C6N7 units. Herein, C3N5 as a photocatalyst for CO2 reduction was investigated by density functional theory methods. The electronic and optical properties indicate that C3N5 has a longer visible-light region with 2.0 eV of band gap in comparison with g-C3N4. The spatial distributions of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) show that the π network of C3N5 is extended by introducing -NN- linkage, which results in much higher photocatalytic efficiency than g-C3N4. The Gibbs free energies for possible CO2 reaction paths on C3N5 were computed. The results show that CO2 can be reduced to CH4 with a low limiting potential of -0.54 V and to CH3CH2OH with a low limiting potential of -0.61 V, which all driven by solar energy. The present work is expected to provide useful guide for new-type nitrogen-rich C3N5 as promising photocatalyst for CO2 reduction reaction (CO2RR).