二维非金属的石墨相氮化碳/共价三嗪骨架异质结构材料用于高效和高选择性光催化二氧化碳还原

2D metal‐free heterostructure of covalent triazine framework/g‐C_(3)N_(4) for enhanced photocatalytic CO_(2) reduction with high selectivity

利用太阳光驱动CO_(2)转化成为有价值的化工品是一种极具前景的降低大气中CO_(2)含量和生产可再生能源的方法,而这种方法主要依赖于具有高效分离载流子能力的光催化剂.本文将石墨相氮化碳(g-C_(3)N_(4),简写为CN)和共价三嗪骨架(CTF)结合的非金属异质结构(CN/CTF)应用于CO_(2)的光催化还原反应中.材料的zeta电位和X射线光电子能谱结果表明,CN和CTF在超声自组装过程中通过静电作用力相结合,并进一步通过共价键作用增强其界面反应形成CN/CTF异质结构.紫外可见漫反射光谱、光致发光光谱和时间分辨荧光衰变光谱等结果表明,CN/CTF异质结构具有较好的可见光吸收性质,同时具备高效分离光生载流子的能力,其电子转移速率达2.04×10^(8)s^(‒1),有助于提高光催化CO_(2)还原效率.CTF的引入可以极大提高CN的光催化活性,当CTF含量为2.5 wt%时CN/CTF异质结构还原CO_(2)生成CO的产率达到151.1μmol/(g·h),可稳定保持30 h,且反应过程中几乎没有CH_(4)的生成,CO生成选择性达99.9%.与单纯的CTF和CN相比,最优条件的CN/CTF异质结构在可见光照射下能更有效地分离载流子,且载流子复合率更低,其光催化CO_(2)还原成CO的产率分别为CTF和CN的25.5倍和2.5倍.与已报道的基于CN和CTF的光催化剂相比,CN/CTF异质结构具有更好的光催化活性、稳定性和还原CO_(2)选择性.莫特肖特基曲线测试等实验结果表明,CN的导带电位和价带电位分别为-1.20和1.73 V,而CTF的分别为-0.78和1.71 V,该能带结构使得CN和CTF形成Ⅰ型异质结,有利于进行CO_(2)/CO的还原反应(氧化还原电位为-0.52 V).在反应动力学上,CN/CTF异质结构光催化CO_(2)还原生成CO仅需两对H+/e−,提高了生成CO的选择性,同时助剂2,2’-联吡啶配合物的加入可加快电子传输效率,实现CO_(2)的吸附断键和光催化还原的动态循环.综上,本文有望为基于太阳光驱动的光催化还原CO_(2)研究领域提供新的高效非金属催化剂.

Solar‐driven CO_(2)conversion to precious fossil fuels has been proved to become a potential way to decrease CO_(2)with producing renewable fuels,which mainly relies on photocatalysts with efficient charge separation.In this work,a metal free heterostructure of covalent triazine framework(CTF)and graphite carbon nitride(g‐C_(3)N_(4),abbreviated as CN)is applied in the CO_(2)photoreduction for the first time.Detailed characterization methods such as photoluminescence(PL)and time‐resolved PL(TR‐PL)decay are utilized to reveal the photo‐induced carries separating process on g‐C_(3)N_(4)/CTF(CN/CTF)heterostructure.The introduced CTF demonstrated a great boosting photocatalytic activity for CN,bringing about the transform rates of CO_(2)to CO reaching 151.1μmol/(g·h)with a 30 h stabilization time,while negligible CH_(4)was detected.The optimal CN/CTF heterostructure could more efficiently separate charges with a lower probability of recombination under visible light irradiation,which made the photoreduction efficiency of CO_(2)to CO be 25.5 and 2.5 times higher than that of CTF and CN,respectively.This investigation is expected to offer a new thought for fabricating high‐efficiency photocatalyst without metal in solar‐energy‐driven CO_(2)reduction.