Atomic simulation of adsorption of SO2 pollutant by metal (Zn, Be)-oxide and Ni-decorated graphene: a first-principles study

Due to the impact of toxic gases on human health, considerable interest has been shown in detecting noxious air pollutants, particularly sulfur dioxide (SO₂), both experimentally and theoretically. This work provides new insights into the adsorbing (SO₂) molecules on the surface of metal-oxide graphitic structures, i.e., Beryllium-Oxide (BeO), Zinc-Oxide (ZnO), and Ni-decorated graphene applying a first-principles study. Computational analyses suggest that the type of binding of SO₂ molecule on BeO and ZnO sheets is physisorption so that binding energies of -0.405 and -0.154 eV were assigned to ZnO and BeO nanosheets in that order. The adsorption energy of SO₂ on metal oxide sheets was much higher than the pristine graphene. Taking pristine graphene as an adsorbent for SO₂ molecule, it was found that such nanomaterial is not an efficient adsorbent due to the weak interactions (-0.157 eV) and low electron charge transfer (0.042 e) present in SO₂/graphene complex. To overcome this issue, graphene nanosheets decorated with nickel atoms were studied for interaction with SO2 molecules; the results indicate that the SO₂ molecules were chemisorbed on Ni-decorated graphene sheets with an adsorption energy of -2.297 eV. Chemisorption of SO₂ molecules on Ni-decorated graphene sheets was proven by the strong orbital hybridization between Ni 3d and sulfur 3p orbitals in the Projected Density of States (PDOS) plot. This work provides useful information about SO₂ adsorption on Ni-decorated graphene sheets in order to develop a new class of gas sensing devices. Superior chemisorption of SO₂ on Ni-decorated graphene sheets compared to the physical adsorption on BeO and ZnO sheets makes Ni-decorated graphene a potential candidate for detecting SO₂ molecules.

A comparison study of C19T (T = C, Cr, Ti, Fe, and Ni) nanocages by first-principle DFT calculation for removal of ozone-destroyer pollutants

In the present work, the interaction of dichloromethane (CH₂Cl₂) and chloroform (CHCl₃) on C₂₀ and C₁₉T (T = Cr, Ti, Fe, Ni) has been studied by density functional theory (DFT). The results have been investigated by binding energy, net charge transfer, electrical and thermodynamic properties, and frontier orbitals. Although the complexes of CH₂Cl₂ and CHCl₃ on free C₂₀ nanocages showed slightly binding energy (- 0.029 and - 0.006 eV, respectively), doping of Cr, Ti, Fe, Ni transition metal atoms on C₂₀ nanocage improved the binding energy. The best binding energy was attributed to the adsorption of CH₂Cl₂ on C₁₉Cr (- 0.755 eV). Based on ESP maps, doping of Cr, Ti, Fe, and Ni is the cause of strong electrophilic region creation which is very useful for adsorption process CH₂Cl₂ and CHCl₃ on nanocages. Also, natural bond orbital (NBO) analysis showed that the best charge transfer was 0.253 eV which was related to the formation of C₁₉Fe-CHCl₃ complex. In addition, the least HOMO-LUMO energy gap between free nanocages (C₂₀, C₁₉Cr, C₁₉Ti, C₁₉Fe, and C₁₉Ni) is 4.05 eV (C₁₉Ti). The thermodynamic investigations indicated that due to the negative enthalpy, all of the studied adsorption processes were exothermic.