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基于第一性原理的密度泛函理论,本文系统研究了氧化石墨烯及其Ag与Cu掺杂对NH3分子的吸附特性.通过计算电荷分布、态密度、能带结构和吸附能,研究了含氧基团及金属掺杂对氧化石墨烯气敏性能的调控效应.通过对掺杂Ag原子的氧化石墨烯的态密度进行分析,发现Ag原子与NH3中的N原子的s、p和d轨道之间存在共振,表明Ag原子和N原子之间形成了化学键.这种化学键导致Ag对NH3的吸附作用明显强于含氧基团,从而使得掺杂后的氧化石墨烯的吸附能提升了数倍.此外,Cu掺杂氧化石墨烯同样能够显著提升其对NH3的吸附性能.在掺杂浓度均为3.13%的条件下,Cu掺杂的氧化石墨烯对NH3表现出更强的吸附能力.同时,Ag或Cu掺杂的氧化石墨烯中,羧基和环氧基对NH3的吸附模式由物理吸附转变为化学吸附；而羟基则在掺杂前后始终显示出化学吸附特性.综上所述,金属掺杂的氧化石墨烯的吸附能会受到含氧基团和金属原子共同作用影响,且Ag或Cu原子掺杂能显著提高氧化石墨烯对NH3的吸附性能.Graphene has attracted great attention due to its large specific surface area,high charge carrier mobility,and excellent electrical conductivity.However,the inherent structural integrity and zero bandgap characteristics of graphene limit its gas sensing properties.Consequently,researchers have embarked on exploring avenues such as doping graphene or leveraging graphene oxide as a gas-sensitive material to design gas sensors that respond optimally to ammonia.This study,based on first-principle density functional theory,focuses on the field of ammonia gas sensors,investigating in detail the adsorption characteristics of ammonia molecules on graphene oxide (GO) and graphene oxide doped with Ag and Cu (AgGO, CuGO).By calculating parameters encompassing charge distribution,density of states,band structures,and adsorption energies,the study delves into the influence of diverse oxygen-containing groups and metal doping on the gas sensing properties of graphene oxide.The research results demonstrate a substantial charge density overlap between the density of states of hydroxyl groups in graphene oxide and NH3 molecules,thereby indicating a pronounced chemical adsorption propensity.Particularly noteworthy is the observation that post-NH3 adsorption,the hydroxyl-containing graphene oxide exhibits the highest charge transfer (0.078e) and adsorption energy (0.60 eV),signifying its superior adsorption efficacy towards NH3,followed by carboxyl groups,with epoxy groups displaying comparably weaker adsorption capabilities, wherein the latter two primarily engage in physical adsorption.Furthermore,the study delves into the impact of metal doping on graphene oxide,evidencing that the adsorption capability of doped graphene oxide hinges upon the synergistic influence of oxygen-containing groups and metal atoms,with Ag-doped graphene oxide showing a several-fold increase in adsorption energy.Through density of states analysis,it transpires that Ag atoms resonate with s,p,and d orbitals of the N atom in NH3,proving the formation of a chemical bond between Ag atoms and N atoms. Moreover,a comparative analysis shows that Cu-doped graphene oxide (CuGO) has an increased charge transfer of about 0.020e and slightly higher adsorption energy compared to Ag-doped graphene oxide (AgGO) when adsorbing NH3.Intriguingly, under the same doping concentration,CuGO exhibits superior adsorption performance towards NH3. Significantly,within Graphene Oxide doped with Ag or Cu,the adsorption mechanism of carboxyl and epoxy groups transitions from physical to chemical adsorption,while the hydroxyl groups maintain consistent chemical adsorption properties pre and post-doping.This suggests that doping with Ag or Cu atoms can significantly enhance the adsorption capability of graphene oxide towards NH3.
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Keywords:
- doping /
- graphene oxide /
- first principle /
- adsorption
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