A solid-state chemical reduction approach to synthesize graphitic carbon nitride with tunable nitrogen defects for efficient visible-light photocatalytic hydrogen evolution
A solid-state chemical reduction approach to synthesize graphitic carbon nitride with tunable nitrogen defects for efficient visible-light photocatalytic hydrogen evolution
复制标题
固态化学还原方法合成具有可调氮缺陷的石墨碳氮化物，用于有效的可见光光催化析氢
DOI：
10.1016/j.jcis.2018.10.012
复制
发表时间：
2019
影响因子：
9.9
通讯作者：
Chen Zhiwu
中科院分区：
文献类型：
--
作者：
Zhang Yizeng;Gao Junning;Chen Zhiwu
具有氮缺陷的石墨氮化碳（g-C3N4-x）是在温和的温度条件下通过简便有效的固态化学还原技术制备的。电子顺磁共振（EPR）、X射线光电子能谱（XPS）、傅里叶变换红外光谱（FTIR）和固态13C MAS NMR谱证明氰基和氮空位可以通过调节化学还原温度来控制。与原始的 g-C3N4 相比，所制备的 g-C3N4-x 在可见光照射下表现出大大增强的光催化析氢活性。 g-C3N4-x在400℃化学还原处理1h后，其最大析氢速率为3068μmol·g−1·h−1，是原始g-C3N4的4.85倍。此外，该光催化剂还表现出优异的重复使用性和储存稳定性。研究发现，氮缺陷可以导致价带上移和导带下移，有利于吸收较长波长的光子和捕获光生电子，从而减少产生的载流子的复合损失。正是由于这种改进的可见光吸收和载流子分离，与原始的 g-C3N4 相比，g-C3N4-x 显示出更好的可见光光催化活性。结论是，本文提出的合成策略代表了一种直接有效的方法，可以协同优化基于 g-C3N4 的光催化剂的化学成分、光学响应和光催化特性。
Graphitic carbon nitride with nitrogen defects (g-C3N4-x) is prepared by a facile and effective solid-state chemical reduction technique at mild temperature conditions. The cyano groups and nitrogen vacancies, as evidenced by electron paramagnetic resonance (EPR), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectra (FTIR) and Solid-state13C MAS NMR spectra, are controllable via adjusting chemical reduction temperature. Comparing to the pristine g-C3N4, the as-prepared g-C3N4-xshows much enhanced photocatalytic H2evolution activity under visible-light irradiation. The maximum H2evolution rate of 3068 μmol·g−1·h−1is achieved with g-C3N4-xafter chemical reduction treatment at 400 °C for 1 h, which is 4.85 times that of the pristine g-C3N4.Moreover, excellent reusability and storage stability have been shown by this photocatalyst as well. It is discovered that nitrogen defects can result in both the up-shift of the valance band and the down-shift of the conduction band, which benefit the absorption of longer wavelength photons and trapping of the photoinduced electrons, therefore reducing the recombination losses of the generated carriers. It is because of this improved visible-light absorption and charge carrier separation, g-C3N4-xdisplays better visible-light photocatalytic activity compared to the pristine g-C3N4. It is then concluded that the synthetic strategy presented here represents a straightforward and efficient way to synergistically optimize the chemical composition, optical response, and photocatalytic characteristics of g-C3N4-based photocatalysts.