高比表面积g-C_3N_4负载Keggin型Cu单晶取代杂多酸特异性光催化还原CO_2制CH_4
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摘要
以三聚氰胺、二水合钨酸钠、二水合磷酸氢二钠、CuCl_2等为原料,采用乙醚萃取法和模板剂法分别制备了Keggin型Cu单晶取代的杂多酸(PW_(11)Cu)和高比表面积g-C_3N_4(PCN),通过浸渍法将PW_(11)Cu负载于PCN上制得催化剂,对制得的催化剂进行了FTIR、XRD、N_2吸附-脱附、UV-Vis漫反射光谱、EIS光谱、荧光光谱表征,通过光催化还原CO_2对催化剂的活性及稳定性进行了考察,并对催化机理进行了探究。表征结果显示,比表面积的增加及PW_(11)Cu的负载均能有效降低光生电子-空穴的复合几率,拓宽光响应范围。实验结果表明,Cu单晶取代杂多酸的负载能够特异性还原CO_2为CH_4,当PW_(11)Cu负载量为15%(w)时表现出最佳的催化活性,且循环使用5次后催化剂的活性没有明显变化。
Using melamine,Na_2WO_4·2H_2O,Na_2HPO_4·2H_2O and CuCl_2 as precursors,Keggin type Cu substituted heteropoly acid potassium(PW_(11)Cu)and high surface area g-C_3N_4(PCN)were synthesized by extraction method with ether and template method,respectively.PW_(11)Cu was loaded on PCN by dipping method.The structure of catalysts was characterized by FTIR,XRD,BET,UV-Vis spectroscopy,EIS spectroscopy and photoluminescence spectrum.The activity and stability of catalysts were tested toward reduction CO_2,and the mechanism of catalysis was also explored.The results indicated that the increase of the surface area and the loaded of PW_(11)Cu could effectively reduce the recombination of the photogenerated electrons and holes,and broaden the range of light response.The result showed that the loading of the PW_(11)Cu could specifically reduce CO_2 to CH_4.The catalyst exhibited the highest photocatalytic activity when the doping amount of PW_(11)Cu was 15%(w)and the activity did not change significantly after 5 cycles.
Using melamine,Na_2WO_4·2H_2O,Na_2HPO_4·2H_2O and CuCl_2 as precursors,Keggin type Cu substituted heteropoly acid potassium(PW_(11)Cu)and high surface area g-C_3N_4(PCN)were synthesized by extraction method with ether and template method,respectively.PW_(11)Cu was loaded on PCN by dipping method.The structure of catalysts was characterized by FTIR,XRD,BET,UV-Vis spectroscopy,EIS spectroscopy and photoluminescence spectrum.The activity and stability of catalysts were tested toward reduction CO_2,and the mechanism of catalysis was also explored.The results indicated that the increase of the surface area and the loaded of PW_(11)Cu could effectively reduce the recombination of the photogenerated electrons and holes,and broaden the range of light response.The result showed that the loading of the PW_(11)Cu could specifically reduce CO_2 to CH_4.The catalyst exhibited the highest photocatalytic activity when the doping amount of PW_(11)Cu was 15%(w)and the activity did not change significantly after 5 cycles.
引文
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[3]Tahir M,Tahir B,Amin N A S,et al.Synergistic effect in plasmonic Au/Ag alloy NPs co-coated TiO2 NWs toward visible-light enhanced CO2 photoreduction to fuels[J].Appl Catal,B,2017,204:548-560.
[4]Patnaik S,Martha S,Madras G,et al.The effect of sulfate pre-treatment to improve the deposition of Au-nanoparticles in a gold-modified sulfated g-C3N4 plasmonic photocatalyst towards visible light induced water reduction reaction[J].Phys Chem,2016,18:28502-28514.
[5]Patnaik S,Martha S,Parida K M.An overview of the structural,textural and morphological modulations of g-C3N4 towards photocatalytic hydrogen production[J].RSC Adv,2016,6:46929-46951.
[6]Lin Zhenzhen,Lin Lihua,Wang Xinchen.Thermal nitridation of triazine motifs to heptazine-based carbon nitride frameworks for use in visible light photocatalysis[J].Chin J Catal,2015,36:2089-2094.
[7]李松田,吴春笃,闫永胜,等.杂多酸光催化降解有机污染物[J].化学进展,2008,20(5):690-697.
[8]Ma Liang,Jia Lihua,Guo Xingfng,et al.Catalytic activity of Ag/SBA-15 for low-t+emperature gas-phase selective oxidation of benzyl alcohol to benzaldehyde[J].Chin J Catal,2014,35(1):108-119.
[9]周广栋,刘延,咸漠,等.第四周期过度金属钨磷杂多酸盐的合成及表征[J].燃料化学学报,2001,29(8):205-207.
[10]金瑞瑞,游继光,张倩,等.Fe掺杂g-C3N4的制备及其可见光催化性能[J].物理化学学报,2014,30(9):1706-1712.
[11]Zhu Anquan,Qiao Lulu,Jia Ziqi,et al.C-S bond induced ultrafine SnS2 dot/porous g-C3N4 sheet 0D/2D heterojunction:Synthesis and photocatalytic mechanism investigation[J].Dalton Trans,2017,46(10):17032-17040.
[12]Yuan Yupeng,Yin Lisha,Cao Shaowen,et al.Microwave-assisted heating synthesis:A general and rapid strategy for large-scale production of high crystalline g-C3N4 with enhanced photocatalytic H2 production[J].Green Chem,2014,16(11):4663-4668.
[13]Li Mengli,Zhang Lingxia,Fan Xiangqian,et al.Highly selective CO2 photoreduction to CO over g-C3N4/Bi2WO6 composites under visible light[J].J Mater Chem A,2015,3(9):5189-5196.
[14]毛丽萍,玉轶聪,史妍,等.Keggin型Sn单取代的杂多酸盐催化合成环己酮[J].精细化工,2017,34(3):300-306.
[15]曲晓钰,胡绍争,李萍,等.镍掺杂石墨相氮化碳的熔盐辅助微波法制备及光催化固氮性能[J].高等学校化学学报,2017,38(12):2280-2288.
[16]Wang Xinchen,Maeda K,Thomas A,et al.A metal-free polymeric photocatalyst for hydrogen production from water under visible light[J].Nat Mater,2009,8(1):159-165.
[17]Zhang Guigang,Zhang Jinshui,Zhang Mingwen,et al.Polycondensation of thiourea into carbon nitride semiconductorw as visible light photocatalysts[J].J Mater Chem A,2012,22(16):8083-8091.
[18]Zou Xiaoxin,Li Guodong,Wang Yuning,et al.Direct conversion of urea into graphitic carbon nitride over mesoporous TiO2 spheres under mild condition[J].Chem Commun,2010,47(3):1066-1068.
[19]Xu Yuanguo,Xu Hui,Wang Lei,et al.The CNT modified white C3N4 composite photocatalyst with enhanced visible-light response photoactivity[J].Dalton Trans,2013,42(41):7604-7613.
[20]Li D,Haneda H,Hishita S,et al.Visible-light-driven N-F-codoped TiO2 photocatalysts.1.Synthesis by spray pyrolysis and surface characterization[J].Chem Mater,2005,17(10):2588-2595.