Influence of 'period four' transition metal doping in graphene on adsorption and transduction characteristics for CO gas- A detailed ab-initio perspective

This work analyses the comparative effects of period-four transition metal (TM) dopants for CO molecular adsorption on the monolayer Graphene (Gr) supercell using the density functional theory (DFT) based ab initio method for the first time. Ten different TM dopant species (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cr, Zn) have been incorporated and extensively studied in the context of Carbon Monoxide (CO) adsorption. The study elaborates on the effects of metallic doping in Gr on structural stability, electronic properties, adsorption strength, transduction efficacy, and CO recovery time. The study reveals that introducing each period-four TM dopant in the Gr lattice changes the semi-metallic nature, wherein distinct modulations in the energy band structure and the total density of state profiles can be observed after CO adsorption in each doped Gr matrix. The C atom of the polar CO molecule preferentially adsorbed on the doped TM, forming physical C-X (X: metal) bonds and resulting in slight vertical displacement of the dopant towards adsorbed CO. The results exhibit that depending on the strength of CO adsorption, the metallic dopants can be placed in the following order: Ti > V > Cr > Mn > Fe > Co > Ni > Cu > Zn > Sc, with a significant improvement in charge transfer during CO adsorption after Sc, Co, Ni, V, and Zn doping in Gr. Specifically, the Ni, Zn, and Sc-doped Gr ensures an efficient trade-off between adsorption stability and recovery time with high selectivity in CO2 and N-2 environments.