Molecular Dynamics Beyond the Monolayer Adsorption as Derived from Langmuir Curve Fitting

Langmuir adsorption model is a classic physical-chemical adsorption model and is widely used to describe themonolayer adsorption behavior at the material interface in environmental chemistry. Traditional adsorption dynamic modeling solelyconsidered the surface physiochemical interaction between the adsorbent and adsorbate. The surface reaction dynamics resultingfrom the heterogeneous surface and intrinsic electronic structure of absorbents were rarely considered within the reportedadsorption experiments. Herein, by employing the chlorine hybrid graphene oxide (GO-Cl) to adsorb Ag+in an aqueous solution,complicated molecular dynamics significantly deviated from the monolayer adsorption mechanism, as suggested by Langmuiradsorption curvefitting, has been elucidated down to atomic scale. In the time-dependent Ag adsorption experiments, both Ag singleatoms and Ag/AgCl nanoparticle heterostructures are observed to be formed sequentially onGO-Cl. These observations indicatethat for the surface adsorption dynamics, not only the surface chemical adsorption process involved but also photoreduction and theC-Cl bond cleavage reaction has been heavily engaged within theGO-Clinterface, suggesting a much more complicated visionrather than the monolayered adsorption algorithm as derived from curvefitting. This study usesGO-Clas a simple example todisclose the complicated adsorption dynamic process underneath Langmuir adsorption curvefitting. It advocates the necessity ofimaging the interfacial atomic-scale dynamic structure with high-resolution microscopy techniques in modern adsorption studies,rather than simply explaining the adsorption dynamics relying on the curvefitting results due to the complicated physiochemicalreactivity of the adsorbents.

Automated summary

The Langmuir adsorption model is widely used in environmental chemistry to describe monolayer adsorption behavior at material interfaces. However, traditional adsorption dynamic modeling often overlooks the surface chemical reaction dynamics of the adsorbent, which is rarely considered in experiments. This study demonstrates through experiments that there is a complex molecular dynamics process occurring at the GO-Cl interface, which significantly deviates from the monolayer adsorption mechanism suggested by Langmuir adsorption curvefitting.