Wang Fengzhi, Lei Weisheng, Pan Xinhua, Lu Bin, Ye Zhizhen
State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University Hangzhou 310027 People's Republic of China
RSC Adv. 2020 May 27;10(34):20110-20117. doi: 10.1039/c9ra10819j. eCollection 2020 May 26.
Photocatalytic hydrogen evolution by water splitting has become a very effective way to solve the energy crisis. For use in that process, graphitic carbon nitride (g-CN) has drawn much attention for its response in the visible region. However, its insufficient sunlight absorption efficiency and easy recombination of photoinduced carriers restrict its photocatalytic activity. Herein, we demonstrate a two-step liquid ultrasonic method in water to synthesize a series of tetracyanoquinodimethane (TCNQ)-CN photocatalysts aiming to form a conjugated structure by 7,7,8,8-TCNQ. g-CN was treated with APTES firstly on its surface in order to give a better interface contact with TCNQ. Benefiting from the conjugation effect between TCNQ and g-CN, the separation and transport efficiency of photogenerated carriers were significantly improved. Besides, introducing TCNQ also broadened the absorption region. Both of these points lead to the enhancement of photocatalytic H production rate, with the optimized 5% TCNQ-CN giving a rate nearly 9.48 times that of pure g-CN. Also, 5% TCNQ-CN (U) was prepared with unmodified g-CN, which exhibited a rate only 6.87 times that of pure g-CN, thus validating the necessity of surface modification. Our work reveals that the rational conjugated structure could modulate the electrical and optical properties of g-CN, yielding an improvement of photocatalytic activities.
通过水分解进行光催化析氢已成为解决能源危机的一种非常有效的方法。在该过程中，石墨相氮化碳（g-CN）因其在可见光区域的响应而备受关注。然而，其阳光吸收效率不足以及光生载流子容易复合限制了其光催化活性。在此，我们展示了一种在水中的两步液体超声法来合成一系列四氰基对苯二甲烷（TCNQ）-CN光催化剂，旨在通过7,7,8,8-TCNQ形成共轭结构。首先用APTES对g-CN的表面进行处理，以便与TCNQ有更好的界面接触。受益于TCNQ与g-CN之间的共轭效应，光生载流子的分离和传输效率得到显著提高。此外，引入TCNQ还拓宽了吸收区域。这两点都导致光催化产氢速率的提高，优化后的5% TCNQ-CN的产氢速率几乎是纯g-CN的9.48倍。同时，用未改性的g-CN制备了5% TCNQ-CN（U），其产氢速率仅为纯g-CN的6.87倍，从而验证了表面改性的必要性。我们的工作表明，合理的共轭结构可以调节g-CN的电学和光学性质，从而提高光催化活性。
