摘要
MXenes have attracted considerable attention owing to their versatile and excellent physicochemi‐cal properties.Especially,they have potential applications as robust support for single atom cata‐lysts.Here,quantum chemical studies with density functional theory are carried out to systemati‐cally investigate the geometries,stability,electronic properties of oxygen functionalized Ti_(2)C(Ti_(2)CO_(2))supported single‐atom catalysts M_(1)/Ti_(2)CO_(2)(M=Fe,Co,Ni,Cu Ru,Rh,Pd,Ag Os,Ir,Pt,Au).A new non‐noble metal SAC Fe_(1)/Ti_(2)CO_(2) has been found to show excellent catalytic performance for low‐temperature CO oxidation after screening the group 8‐11 transition metals.We find that O_(2) and CO adsorption on Fe_(1) atom of Fe_(1)/Ti_(2)CO_(2) is favorable.Accordingly,five possible mechanisms for CO oxidation on this catalyst are evaluated,including Eley‐Rideal,Langmuir‐Hinshelwood,Mars-van Krevelen,Termolecular Eley‐Rideal,and Termolecular Langmuir‐Hinshelwood(TLH)mechanisms.Based on the calculated reaction energies for different pathways,Fe_(1)/Ti_(2)CO_(2) shows excellent kinet‐ics for CO oxidation via TLH mechanism,with distinct low‐energy barrier(0.20 eV)for the rate‐determining step.These results demonstrate that Fe_(1)/Ti_(2)CO_(2) MXene is highly promising 2D materials for building robust non‐noble metal catalysts.
单原子催化剂是一类新型的环境友好催化材料,在能源有效利用和环境保护中发挥着至关重要的作用.发展廉价高效的贵金属催化剂具有十分重要的科学意义和实用价值.近年来,非贵金属部分或者全部取代贵金属的研究也备受关注,成为催化领域的研究热点之一.MXene是由MAX相刻蚀得到的新型类石墨烯结构.MAX相的分子式为M_(n+1)AX_(n)(n=1,2,3),其中M代表前过渡金属,A代表主族元素,X代表C和/或N元素.由于M‒X具有较强的化学键能,A具有较活泼的化学活性,因此,可以通过选择性刻蚀作用将A从MAX相中移除,从而得到类石墨烯的2D结构—MXene.各类MXenes二维材料因具有广泛的应用价值和较好的物理化学性能而引起了人们的广泛关注,尤其在单原子催化方面,MXenes表现出巨大的应用潜力.本文选取氧功能化的Ti_(2)C(Ti_(2)CO_(2))MXene二维材料为载体,系统研究了其负载的金属单原子催化剂(SACs)的稳定性和催化活性.通过筛选周期表第8‒11族过渡金属M_(1)/Ti_(2)CO_(2)(M=Fe,Co,Ni,Cu,Ru,Rh,Pd,Ag,Os,Ir,Pt,Au),筛选出了一种新的非贵金属单原子催化剂Fe_(1)/Ti_(2)CO_(2),发现其对CO氧化反应具有极高的催化活性.基于密度泛函理论(DFT)计算,使用VASP从头算模拟软件对上述体系进行了结构优化以及性质的计算,选取了广义梯度近似(GGA)中的PBE泛函,采用投影缀加平面波(PAW)方法描述体系中电子-离子的相互作用.计算结果表明,O_(2)和CO分子易于在Fe_(1)/Ti_(2)CO_(2)表面的Fe1单原子上吸附活化.基于O_(2)和CO分子不同的吸附构型,对Fe_(1)/Ti_(2)CO_(2)催化CO氧化包括Langmuir-Hinshelwood(L-H),Eley-Rideal(E-R),Mars-van Krevelen(MvK),三分子Eley-Rideal(TER)和三分子Langmuir-Hinshelwood(TLH)可能的五种反应机理进行了理论研究.结果表明,L-H,E-R,Mvk,TER和TLH反应的决速步骤均为形成第一个CO_(2)分子的过程,其活化能分别为0.95,0.77,2.27,0.98和0.20 eV,而第二个CO
基金
国家自然科学基金(21963005,21763006,22033005)
陕西省催化重点实验室开放课题(SXKLC-2017-01)
广东省催化重点实验室(2020B121201002)
广东省“珠江人才计划”(2019QN01L353)
贵州大学自然科学基金([2021]40,[2020]32)。
