天然闪锌矿光催化还原二氧化碳实验研究

Experimental study of photocatalytic reduction of carbon dioxide on natural sphalerite

利用电子探针(EPMA),X射线光电子能谱(XPS),拉曼光谱(Raman)和紫外可见漫反射(UV-vis DRS)对天然闪锌矿成分、物相与能带结构进行了表征,发现Fe,Cu,Ga等杂质金属可抬升闪锌矿价带能级位置,减小禁带宽度,并在其禁带中引入施主与受主能级,增强闪锌矿的光吸收范围.在pH为6的厌氧条件下,光照9h后天然闪锌矿光催化还原CO_2产生的甲酸浓度达到12mg·L^(-1),高于合成ZnS的10mg·L^(-1).当NaH_2PO_2与Na_2S作为复合空穴捕获剂时,CO_2光催化还原速率较由Na_2S作为空穴捕获剂的体系提升45%.在此基础上,根据实验介质环境下闪锌矿表面荷电特性,探讨了闪锌矿对CO_2的吸附方式影响CO_2还原效率并降低CO_2转化为CO_2^-阴离子能垒的微观机制.研究结果可扩展天然半导体矿物作为低成本、大产量光催化剂在CO_2有机转化领域的应用范围.

The chemical composition,mineral phase and band structure were analyzed by electron probe microanalyzer（EPMA）,Raman,X-ray photoelectron spectroscopy（XPS）and UV-vis diffuse reflectance spectroscopy（UVvis DRS）.The dopants including Fe,Cu,Ga raised valence band position and introduced donor level and acceptor level to band structure of natural sphalerite,expanding the light absorption range.In weak acidic and anaerobic solution,the yield of HCOOH photo-reduced by natural sphalerite was 12mg·L^（-1） after irradiation for 9h,higher than synthetic ZnS.The synergistic effect in the use of both NaH_2PO_2 and Na_2S as hole scavenger was also discussed.According to the point of zero charge（PZC）of sphalerite,a micro mechanism was proposed to reveal the process of photocatalytic reduction on natural sphalerite surface.Our research might explore the application of natural semiconducting minerals as cost-effective photocatalysts and provide direction to accelerate photoreduction of CO_2 by surface modification.