钴盐辅助离子热：新策略助力聚合物氮化碳光催化制氢性能显著提升

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Boosting photocatalytic hydrogen production by creating isotype heterojunctions and single-atom active sites in highly-crystallized carbon nitride

Shaohua Shen, Jie Chen, Yiqing Wang, Chung-Li Dong, Fanqi Meng, Qinghua Zhang, Yiliang Huangfu, Zhi Lin, Yu-Cheng Huang, Yanrui Li, Mingtao Li, Lin Gu

Science Bulletin, 2022, 67(5): 520–528

doi: 10.1016/j.scib.2021.11.024

中文导读

聚合物氮化碳在光催化制氢应用中展示了巨大潜力. 研究人员提出了一种同时构建高结晶氮化碳同型异质结并构筑单原子活性位点的策略. 他们发现在离子热合成中加入钴盐, 能促进庚嗪基结晶氮化碳(CCN)向三嗪基结晶氮化碳(PTI)的相变, 同时, 钴盐可作为单原子钴活性位点的金属源. 该Co-CCN/PTI光催化剂在425 nm处达到了20.88%的表观量子效率, 在可见光波段(λ > 420 nm)达到了3538 μmol h⁻¹ g⁻¹的制氢速率, 该速率比CCN高4.8倍, 比PTI高27.6倍. 分析结果表明,CCN/PTI之间的Type II同型异质结可有效促进电荷分离, Co单原子活性位点可加速表面氧化反应, 这两方面因素同时促进光催化制氢性能的提高.

图文速览

Fig. 1 (a) XRD patterns of Co-CCN/PTI-x (x = 0, 2, 4, 10, 20, 40). (b) HRTEM image of Co-CCN/PTI-0. (c) HRTEM image of Co-CCN/PTI-4. (d) The magnified selected area marked in (c). (e) Selected area electron diffraction (SAED) pattern of Co-CCN/PTI-4. (f) HRTEM image of Co-CCN/PTI-40. (g) N 1s XPS spectra of Co-CCN/PTI-x (x = 0, 2, 4, 10, 20, 40). (h) C K-edge XANES spectra of Co-CCN/PTI-0, Co-CCN/PTI-4 and Co-CCN/PTI-40. Inset shows the magnified selected area.

Fig. 2 (a) HAADF-STEM image of Co-CCN/PTI-4. (b) FT k³-weighted Co K-edge EXAFS spectra of Co-CCN/PTI-4, Co-CCN/PTI-40 and the references. (c) Topographical maps of WT-EXAFS of Co-CCN/PTI-4, Co-CCN/PTI-40 and the references. FT-EXAFS fitting curves of (d) Co-CCN/PTI-4, (e) Co-CCN/PTI-40 at Co K-edge. The inset of (d) and (e) shows the structure models of Co-CCN and Co-PTI, respectively, where the sp²-hybridized nitrogen (C=N-C) is denoted as N1 and the amino nitrogen (C−N−H) was denoted as N2.

Fig. 3 (a) Photocatalytic hydrogen production rates over different amounts (10, 20, 50, 100 mg) of Co-CCN/PTI-4 photocatalysts. (b) Photocatalytic hydrogen production rates over CCN/PTI, PTI and Co-CCN/PTI-x (x= 0, 2, 4, 10, 20, 40) using 50 mg of photocatalyst. (c) Wavelength dependent photocatalytic hydrogen production rate over Co-CCN/PTI-4. (d) Cycling photocatalytic hydrogen production activity over Co-CCN/PTI-4. 1.5 mL TEOA was supplemented after 6 hours (2 cycles) of photocatalytic test, and 1.0 mL TEOA was supplemented after another 9 hours (another 3 cycles) of photocatalytic test.

Fig. 4 (a) Schematic illustration of the Type II band alignment within the CCN/PTI isotype heterojunction. (b) The steady-state PL emission spectra of Co-CCN/PTI-x (x = 0, 2, 4, 10, 20,40). Inset shows the zoomed-in PL emission spectra of Co-CCN/PTI-x (x = 10, 20, 40). (c) SPV spectra of CCN/PTI-0, Co-CCN/PTI-4 and Co-CCN/PTI-40. (d) Transient photocurrent responses of CCN/PTI-0, Co-CCN/PTI-4and Co-CCN/PTI-40 under Xe lamp irradiation at a potential of 0.6 V (vs. Ag/AgCl).

Fig. 5 (a) The electron and hole effective mass (unit: m_e) of CCN, Co-CCN, PTI, and Co-PTI. (b) The chemisorption energy for the adsorption of some organic sacrificial reagents (TEOA, methanol, ethanol andformic acid) to the surface of CCN, Co-CCN, PTI, and Co-PTI.

Fig. 6 Schematic mechanisms of the Co-CCN/PTI heterojunction for photocatalytic hydrogen production.

本文通讯作者

沈少华 教授西安交通大学能源与动力学院动力工程多相流国家重点实验室, 主要研究领域为太阳能光/电/热催化制氢与碳氢燃料及其多相反应流与多相界面过程.