Sensing and conversion of carbon dioxide to methanol using Ag-decorated zinc oxide nanocatalyst

Abstract

The catalytic hydrogenation of CO₂ to methanol, which is one of the most important byproducts, has been studied using density functional theory simulations. The chemisorption of silver (Ag) atoms on the ZnO nanocage surface significantly narrowed the bandgap from 4.05 to 1.27 eV and altered the overall optoelectronic and catalytic properties of the nanocage. We introduced a successful two step activation and conversion of carbon dioxide into methanol and water. The high performance of the Ag-decorated ZnO catalyst activated the CO₂ gas owing to its chemisorbed nature. At this stage, three H₂ molecules were incorporated to surround the chemisorbed CO₂ gas, which converted it to methanol (CH₃OH) and water molecules with an enhanced sensitivity of 70%. This demonstrates maximum sensing response up to 54% at room temperature (300 K), which further lowered the bandgap from 1.23 to 0.70 eV. The calculated recovery time of the Ag-decorated ZnO sensor was 5.06 × 10⁻⁰⁹ s, indicating its outstanding optical characteristics, strong chemical stability, and high electron mobility. The adsorption energies of the Ag-decorated and activated CO₂-adsorbed ZnO complexes were found to be −1.76, and −0.28 respectively, indicating a thermodynamically stable configuration. This study focuses on CO₂ activation, advances the catalytic hydrogenation of CO₂ to methanol to develop high-performance catalysts with enhanced sensing responses and recovery times, and provides insight into the reaction mechanisms.