Ag-ZnO/生物质炭纳米复合材料的制备及协同可见光催化性能

以醋酸锌(Zn(CH3COO)2·2H2O)为锌源、硝酸银(AgNO3)为掺杂源、纤维素纳米晶体(Cellulose nanocrystal, CNC)为生物模板,通过溶胶-凝胶法结合碳化处理,制备了Ag-ZnO/生物质炭(Biochar)复合材料。采用TEM、XRD、BET、UV-Vis DRS对所制得的Ag-ZnO/Biochar复合材料进行表征。以亚甲基蓝(MB)为模型污染物,评价Ag-ZnO/Biochar复合材料在可见光源照射下的光催化性能,进一步阐明其光催化机制。结果表明:碳化后纳米ZnO仍保持良好的分散性,球形Ag纳米粒子均匀分散在ZnO表面,形成Ag-ZnO/Biochar三元复合材料。与Ag-ZnO和ZnO/Biochar复合材料相比,Ag-ZnO/Biochar复合材料在可见光下的光催化降解率显著提高。这是由于生物质炭赋予复合体系良好的吸附性能,使MB的光催化降解反应持续发生;而Ag纳米粒子的表面等离子体共振(Surface plasmon resonance, SRP)效应则增强了复合体系在可见光区的吸收。其中,当AgNO3、CNC、Zn(CH3COO)2·2H2O的质量比为0.01:0.25:1时,制得的Ag-ZnO/Biochar复合材料在可见光下具有最佳的光吸收性能和MB降解效率:室温条件下,黑暗中吸附30 min,再用可见光照射120 min,即可达到99%的MB降解率,显著高于Ag-ZnO(约23%)和ZnO/Biochar复合材料(约64%)。

Preparation and synergetic visible-light photocatalysis properties of Ag-ZnO/Biochar nanocomposites

Biochar loaded Ag-doped ZnO composites (Ag-ZnO/Biochar) were prepared with a procedure of sol-gel method and carbonization using zinc acetate (Zn(CH₃COO)₂·2H₂O) as a zinc source, silver nitrate (AgNO₃) as doping source, and cellulose nanocrystal (CNC) as a morphological-inducing template, respectively. The obtained Ag-ZnO/Biochar composites were characterized by TEM, XRD, BET and UV-Vis DRS. The photocatalysis performance of Ag-ZnO/Biochar composites was investigated through the degradation of methylene blue (MB) under visible-light irradiation, and the photocatalysis mechanism of Ag-ZnO/Biochar composites was further studied. The results show that nano ZnO retains a good dispersion after carbonization, and Ag spherical nanoparticles are uniformly dispersed on the surface of ZnO to form Ag-ZnO/Biochar ternary composite. Compared with Ag-ZnO and ZnO/Biochar composites, the photocatalysis property of Ag-ZnO/Biochar composites in the visible-light region is significantly improved, which is attributed to the adsorption ability from biochar and the surface plasmon resonance (SPR) effect from Ag nanoparticles. In particular, the Ag-ZnO/Biochar composites has the best light absorption performance and an optimum degradation efficiency to MB at the mass ratio of 0.01:0.25:1 (AgNO₃:CNC:Zn(CH₃COO)₂·2H₂O), corresponding to 99% degradation rate of MB after the absorption for 30 min in dark condition and continuous irradiation for 120 min under 500 W visible-light at room temperature, which is significantly higher than Ag-ZnO (about 23%) and ZnO/Biochar composites (about 64%).