MXenes are two-dimensional transition metal carbides and nitrides, which are promising for supercapacitor applications. The surface of MXenes is usually covered by a mixture of O, OH, and F groups during etching. The effect of mixed termination on the quantum capacitance and work function (WF) of MXenes is investigated by first principles calculation. The WFs of Sc₂C(OH)₂-R are smaller than those of Sc₂CO₂-R and Sc₂CF₂-R when the OH ratio is larger than about 27 %. The quantum capacitances of Sc₂C MXenes with different ratio of F, O, and OH groups (named as Sc₂CF₂-R, Sc₂CO₂-R, Sc₂C(OH)₂-R) are explored to predict the electrode type of materials. Negative binding energies confirm the stability of the studied mixed systems. The increasing ratio of O group can make the system have decreased TDOS near Fermi level, thus decreasing quantum capacitance. The top quantum capacitance of Sc₂CO₂-R and Sc₂C(OH)₂-R systems at negative bias increase with the increasing ratio of O/OH group. All systems have larger storage charge at negative potential, and are all potential cathode materials, especially for Sc₂CO₂-R and Sc₂CF₂-R MXene with much smaller |Q_a|/|Q_c| than 1 and larger C_c. The quantum capacitance under wide voltage is also considered.

MXenes 是二维过渡金属碳化物和氮化物，在超级电容器应用中具有广阔的前景。在蚀刻过程中，MXenes 的表面通常被 O、OH 和 F 基团的混合物覆盖。通过第一原理计算研究了混合终止对 MXene 的量子电容和功函数 (WF) 的影响。当OH比率大于约27％时， Sc ₂ C(OH) ₂ -R的WF小于Sc ₂ CO ₂ -R和Sc ₂ CF _{2 -R的WF。}研究了具有不同F、O和OH基团比例的Sc ₂ C MXenes（命名为Sc ₂ CF ₂ -R、Sc ₂ CO ₂ -R、Sc ₂ C(OH) ₂ -R）的量子电容，以预测电极材料的类型。负结合能证实了所研究的混合系统的稳定性。O基团比例的增加可以使体系的TDOS降低到费米能级附近，从而降低量子电容。负偏压下Sc ₂ CO ₂ -R和Sc ₂ C(OH) ₂ -R体系的顶部量子电容随着O/OH基团比例的增加而增加。所有体系在负电位下都具有较大的存储电荷，并且都是潜在的正极材料，特别是对于|Q _a |/|Q _c |小得多的Sc ₂ CO ₂ -R和Sc ₂ CF _{2 -R MXene。}大于1且更大的C _c。还考虑了宽电压下的量子电容。