Quantum chemical study on adsorption of hydrogen chloride on Zn-doped carbon materials

In previous studies of HCl adsorption on Zn-doped O2 activated carbon (AC) at 100 and 300 °C, we revealed that Zn-doped carbon adsorbed far more HCl than undoped carbon. However, the effect of metals on the adsorption capability of AC and the mechanism of the adsorption stability of HCl have not yet been clarified. Herein, we used molecular orbital (RHF/6-31G∗) calculations for three carbon active site models (Armchair, Zigzag, and Tip types) to investigate the effect of Zn doping on HCl adsorption via the estimation of the electronic states. The molecular models of the carbon materials with or without Zn doping showed that the presence of Zn increased the number of active sites available for the chemical adsorption of HCl molecules. Furthermore, Zn did not contribute to the adsorption stability of HCl in the Zigzag type model. Zn doping was found to change the electronic state of the active site of the carbon material in the direction in which HCl was readily adsorbed. This study lays the conceptual foundation for suppressing the formation of environmentally harmful volatile compounds from HCl generated in high-temperature processes via the modification of carbon materials to increase HCl adsorption. [Display omitted] •The behavior of HCl adsorption on metal catalyst Zn-doped carbon was clarified.•The Tip type stabilized HCl adsorption the most, followed by the Armchair type.•The Zigzag type showed charge polarization near the active sites without Zn doping.•All three models exhibited polarization near the active sites with ZnO doping.