Reduction kinetics and carbon deposit for Cu-doped Fe-based oxygen carriers: Role of Cu

By combining macroscopic kinetic modeling and density functional theory (DFT) calculations, reduction kinetics and carbon formation of Cu-doped Fe-based oxygen carriers are investigated to reveal the role played by Cu. Compared to undoped Fe-Zr oxygen carrier, 1 mol% Cu dopant enhances reduction rate in the first two reactions (Fe2O3 & nbsp;->& nbsp;Fe3O4 (R-1) and Fe3O4 & nbsp;-> Fe1-xO (R-2)) and hinders carbon formation. This is a result of Cu doping reducing the activation energies of R-1 and R-2 (i.e. R-1: 90.6 & nbsp;-> 56.5 kJ.mol(-1), R-2: 225.9 -> 192.2 kJ.mol(-1)), and increasing the formation energy of carbon-carbon chain on the surface of reduced material. Grain model indicates that Cu dopant promotes oxygen ion migration in bulk material and improves reduction reaction rate constant in R-1 and R-2. However, higher activation energy is found for R-3 (Fe1-xO & nbsp;->& nbsp;Fe), because the formation of an oxygen vacancy becomes harder as the reduction reaction processes. (C)& nbsp;2021 Elsevier Ltd. All rights reserved.

Automated summary

By combining macroscopic kinetic modeling and density functional theory calculations, the reduction kinetics and carbon formation of Cu-doped Fe-based oxygen carriers were investigated. It was found that Cu doping can enhance the reduction rate and inhibit carbon formation by reducing the activation energies and increasing the formation energy of carbon-carbon chains on the material surface. Cu dopant also promotes oxygen ion migration and improves the reduction reaction rate constant.