Role of Atmospheric CO₂ and H₂O Adsorption on ZnO and CuO Nanoparticle Aging: Formation of New Surface Phases and the Impact on Nanoparticle Dissolution

Abstract

Heterogeneous reactions of atmospheric gases with metal oxide nanoparticle surfaces have the potential to cause changes in their physicochemical properties including their dissolution in aqueous media. In this study, gas-phase CO 2 adsorption on ZnO and CuO nanoparticle surfaces was studied as a function of relative humidity to better understand the role of CO 2 and H 2 O on nanoparticle aging and the influence of this aging process on metal ion dissolution from nanoparticles. Upon nanoparticle exposure to atmospherically relevant pressures of CO 2 under different relative humidity (RH) conditions, temporal variations of surface-adsorbed species were monitored using Fourier transmission infrared spectroscopy (FTIR). Under dry conditions, gas-phase CO 2 readily reacts with surface hydroxyl groups present on the ZnO and CuO nanoparticle surface to form adsorbed bicarbonate, whereas the interaction of CO 2 with surface defect sites and lattice oxygen gives rise to surface-adsorbed monodentate and bidentate carbonate species as well as adsorbed carboxylate. With increasing relative humidity from 0 to 70%, surface speciation gradually changes to that of watersolvated adsorbed carbonate, which was the only detectable surface species at the highest relative humidity investigated (70% RH). High-resolution TEM analysis of reacted ZnO and CuO nanoparticles revealed considerable surface restructuring consistent with the precipitation of crystalline carbonate phases in the presence of adsorbed water. Furthermore, the restructuring of ZnO and CuO nanoparticles during CO 2 exposure is limited to the near surface region. Importantly, the reacted ZnO nanoparticles also show an increase in the extent of their dissolution when placed in aqueous media. Thus, this work provides valuable insights into reactions of atmospheric gases, CO 2 and H 2 O, on ZnO and CuO nanoparticle surfaces and the irreversible changes such reactions can induce on nanoparticle surface chemistry and behavior in aqueous media.

On the origin of the elusive first intermediate of CO 2 electroreduction

“…S19C). The proposed assignment of the carboxylate peaks is in good agreement with literature data for alkali metal-CO 2 − and macrocycle-CO 2 − adducts, as well as for *CO 2 − formed on metals and metal oxides from gas phase (16,17,48,49,(63)(64)(65)(66). In particular, the ν as CO 2 − and ν s CO 2 − peaks of *CO 2 − on transition metals have been reported at 1,530-1,660 and 1,130-1,350 cm −1 , respectively, while its δCO 2 − peak, at 650-820 cm −1 (16,17,48).…”

“…In particular, the ν as CO 2 − and ν s CO 2 − peaks of *CO 2 − on transition metals have been reported at 1,530-1,660 and 1,130-1,350 cm −1 , respectively, while its δCO 2 − peak, at 650-820 cm −1 (16,17,48). The *CO 2 − formed from gas phase on CuO nanoparticles and supported Cu has been associated with peaks at ∼1,535 and 1,210 cm −1 (64,65). Peaks at 1,529-1,520 and 1,347-1,310 cm −1 characterize CO 2 activated on a Co(I) macrocycle in wet acetonitrile (66).…”

Synthesis of monocarboxylic acids via direct CO2 conversion over Ni–Zn alloy catalysts

“…This hypothesis was supported by the strong interactions between the CO 2 molecules adsorbed at the medium basic sites and the catalyst surface at the reaction temperatures and facile desorption of the reaction products from the catalyst surface after the reaction. 90,91 . The reaction between monodentate carbonate and adsorbed H 2 produced bicarbonate, which generated the peaks at 1636 cm − 1 (ν as (O − C−O)), 1419 cm − 1 (ν s (O − C−O)), and 1219 cm − 1 (δ(-COH)) 90 .…”

Regeneration of dust filters challenged with metallic nanoparticles: Influence of atmospheric aging

“…Zinc oxide (ZnO) presence in the filter cake, as found by XRD results, is due to the oxidation of zinc during thermal spraying (arc temperature of about 6000 °C) and to exposure to atmospheric oxygen. Gankanda et al (2016) studied the atmospheric aging of ZnO nanoparticles. They found that the reaction of atmospheric CO 2 and H 2 O (at different relative humidity) with the nanoparticles was responsible for the formation of hydrozincite.…”