Insights into $CO_{2}$ activation on defective ZnS surfaces

TL;DR

This study combines experimental and computational methods to show that defective ZnS surfaces can activate CO2 at elevated temperatures, with defect sites playing a crucial role in adsorption and reactivity.

Contribution

It provides new insights into how zinc vacancies on ZnS surfaces facilitate CO2 activation, informing catalyst design for CO2 capture and conversion.

Findings

CO2 adsorbs on defective ZnS above 473 K

Adsorption persists after cooling to room temperature

Oxygen adsorption is exothermic on defective surfaces

Abstract

In this work, we investigate $CO_{2}$ activation on ZnS using Near Ambient-Pressure X-ray photoelectron spectroscopy measurements (NAP-XPS) and density functional theory calculations (DFT). Our NAP-XPS experiments reveal that $CO_{2}$ adsorbs onto a defective ZnS surface upon heating above $473 \ K$ in a $CO_{2}$ atmosphere (up to $0.55 \ mbar$). The $CO_{2}$ adsorption fingerprint is detectable even after cooling to room temperature under ultra-high vacuum. Our DFT calculations suggest that $CO_{2}$ adsorption is energetically favorable on ZnS surfaces containing zinc vacancies, highlighting defect sites as key adsorption centers. Additionally, oxygen adsorption on a defective ZnS surface is exothermic, in contrast to the endothermic behavior observed on a defect-free surface. These findings contribute to a deeper understanding of defect-driven surface reactivity and may inform ZnS-based catalyst's design for $CO_{2}$ capture and reutilization.