Effects of Surface Defects on Photocatalytic H2O2 Production by Mesoporous Graphitic Carbon Nitride under Visible Light Irradiation
Effects of Surface Defects on Photocatalytic H2O2 Production by Mesoporous Graphitic Carbon Nitride under Visible Light Irradiation
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DOI：
10.1021/acscatal.5b00408
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发表时间：
2015-05-01
期刊：
影响因子：
12.9
通讯作者：
Hirai, Takayuki
中科院分区：
文献类型：
--
作者：
Shiraishi, Yasuhiro;Kofuji, Yusuke;Hirai, Takayuki
采用硅模板热聚合法制备了不同比表面积的介孔石墨氮化碳（GCN）催化剂，在可见光（λ> 420 nm）照射下，对乙醇（EtOH）和分子氧（O-2）光催化生成过氧化氢（H2 O2）进行了研究。在这些催化剂上，光形成的正空穴氧化EtOH和导带电子定位在1，4-位置的的Al 2 O3单元促进O-2的双电子还原（H2 O2形成）。具有56和160 m（2）g（-1）表面积的GCN催化剂表现出比不使用二氧化硅模板制备的催化剂（表面积：10 m（2）g（-1））更高的H2 O2生产活性，但是表面积的进一步增加（228 m（2）g（-1））降低活性。此外，H2 O2形成的选择性显著降低。具有较大表面积的介孔GCN固有地在表面介孔处含有大量伯胺部分。这些缺陷的行为作为四电子还原O-2的活性位，从而降低H2 O2的选择性。此外，这些缺陷也表现为所形成的H2 O2的光催化分解的活性位点。因此，具有相对大的表面积但具有少量表面缺陷的GCN催化剂促进相对有效的H2 O2形成。
Photocatalytic production of hydrogen peroxide (H2O2) from ethanol (EtOH) and molecular oxygen (O-2) was carried out by visible light irradiation (lambda > 420 nm) of mesoporous graphitic carbon nitride (GCN) catalysts with different surface areas prepared by silica-templated thermal polymerization of cyanamide. On these catalysts, the photoformed positive hole oxidize EtOH and the conduction band electrons localized at the 1,4-positions of the melem unit promote two-electron reduction of O-2 (H2O2 formation). The GCN catalysts with 56 and 160 m(2) g(-1) surface areas exhibit higher activity for H2O2 production than the catalyst prepared without silica template (surface area: 10 m(2) g(-1)), but a further increase in the surface area (228 m(2) g(-1)) decreases the activity. In addition, the selectivity for H2O2 formation significantly decreases The mesoporous GCN with larger surface areas inherently contain a larger number of primary amine moieties at the surface mesopores. These defects behave as the active sites for four-electron reduction of O-2, thus decreasing the H2O2 selectivity. Furthermore, these defects also behave as the active sites for photocatalytic decomposition of the formed H2O2. Consequently, the GCN catalysts with relatively large surface area but with a small number of surface defects promote relatively efficient H2O2 formation.