(654d) DFT Study of H2s Binding on Cu2o Oxygen Carrier for Chemical Looping with Oxygen Uncoupling (CLOU)

Considerations into the long-term effects of toxic emissions have become a primary concern given the ongoing evidence of climate change. Carbon capture technologies such as pre, post, and oxy-fuel combustion have become prevalent in industrial processes; however, chemical looping with oxygen uncoupling (CLOU) has given rise to a more efficient, low energy alternative, which bypasses N₂ separation in the product stream. A CLOU process, where coal is implemented as fuel, relies on the usage of a metal oxide to supply oxygen to the system as opposed to air. Research into metal oxide materials has consistently proven Cu-based oxides to be optimal for a CLOU process. While CLOU successfully contributes to the efficiency of carbon capture technologies, there is a risk of the resultant S species coming from the gasified coal forming secondary species, such as H₂S, which may adsorb onto the metal oxide surface potentially leading to the depletion of available O₂ sites.

To gain a better understanding of the interaction of sulfur species with the oxygen carrier material, theoretical studies employing density functional theory (DFT) with the Vienna ab Initio Simulation Package (VASP) and ab initiothermodynamics calculations were carried out for a Cu-based oxygen carrier. Cu₂O (111) surface was selected to represent the reduced state of the oxygen carrier after it was exposed to the fuel. Binding and dissociation of H₂S at various sites on the Cu₂O (111) surface were studied. In order to simulate the CLOU reactor environment, flue gas species such as H₂O and CO₂ were included as co-adsorbents on the surface at various surface coverages. Density of state calculations provided further quantum-based insight regarding the electronic adsorbent-surface interactions. Thermodynamic approximations relevant to experimental CLOU conditions were also carried out for H₂S on Cu₂O (111) at varying partial pressures and temperatures.