Synthesis and electrochemical behavior of monolayer-Ti_(3)C_(2)T_(x) for capacitive deionization

单层Ti_(3)C_(2)T_(x)的合成和电化学行为及其电容脱盐应用

MXene materials have got great attention from researchers of environmental treatment for the great electrochemical performance.Monolayer-Ti_(3)C_(2)T_(x)(T_(x) is the surface terminal groups such as-O,-OH and/or-F species),as a typical structural MXene,always shows better chemical-physical characteristics than multilayer-Ti_(3)C_(2)T_(x).Thus,we prepared monolayer-Ti_(3)C_(2)T_(x) electrode by HF etching method and absolute ethyl alcohol intercalationdelamination treatment for capacitive deionization(CDI).The prepared monolay-Ti_(3)C_(2)T_(x) shows a higher specific surface area(235.6 m^(2)/g)and a thinner thickness(0.8 nm).Moreover,a series of systematic investigation demonstrated that monolayer-Ti_(3)C_(2)T_(x) has obvious promotional phenomenon on electrochemical properties(e.g.,mass specific capacitance increased from 52.1 F/g to 144.7 F/g).The NaCl adsorption capacity of monolayer-Ti_(3)C_(2)T_(x),is 30.7 mg/g in 1000 mg/L NaCl solution at 1.2 V.We concluded that the electro-sorption mechanism could be expressed as double electric layer and monolayer coverage by a good fitting of Langmuir isotherms and the pseudo-second-order kinetics equation.This work would provide a new strategy for the application of monolayer-Ti_(3)C_(2)T_(x) material in wastewater treatment in the future.

MXene材料因其优异的电化学性能在环境处理领域受到广泛关注。其中Ti_(3)C_(2)T_(x)(T_(x)代表材料表面官能团如—O、—OH和—F)作为一种典型的MXene材料,其单层结构的化学物理特性较多层结构更优。因此,本文通过HF刻蚀MAX方法获得多层Ti_(3)C_(2)T_(x),再通过无水乙醇插层-剥离处理制备了单层Ti_(3)C_(2)T_(x)材料,并组装成单层Ti_(3)C_(2)T_(x)电极进行电容脱盐应用。单层Ti_(3)C_(2)T_(x)材料厚度为0.8 nm,比表面积为235.6 m^(2)/g。结果表明单层Ti_(3)C_(2)T_(x)电化学性能得到了明显的改善,质量比电容量由52.1 F/g提升至144.7 F/g。在1000 mg/L NaCl溶液中,电压为1.2 V的条件下,单层Ti_(3)C_(2)T_(x)对NaCl的吸附量为30.7 mg/g,该吸附过程可以采用Langmuir等温线和准二级动力学方程进行描述,推测电吸附机理可以表示为双电层上发生的单层吸附过程。此工作为MXene基材料处理废水提供思路。