Adsorption mechanisms of NH3 on ZrO2 in the N-desorption reaction of the chemical looping ammonia generation

Abstract

ZrO2 inhibits the high-temperature decomposition of NH3 by adsorbing it onto the surface in the N-desorption reaction of the chemical looping ammonia generation. We obtained the crystal morphology of m-ZrO2 and investigated the adsorption mechanism of NH3 on the surface of m-ZrO2 (011) using density functional theory calculations with the generalized gradient approximation (DFT-GGA). The surface (011) was found to be the most likely to appear on m-ZrO2, with a probability of 45.187%. The adsorption sites of NH3 on m-ZrO4 (011) were Zr4 and Zr6. N can form unstable chemical bonds with Zr4 and Zr6. Meanwhile, the density states of N between Zr4 and Zr6 have distinct resonance regions. In turn, NH3 formed unstable adsorption on m-ZrO2 (011), which allowed NH3 transfer on m-ZrO2 (011) and inhibited the high-temperature decomposition of NH3 during the N-desorption reaction.

Keywords

• Chemical looping ammonia generation (CLAG)
• Adsorption mechanisms
• DFT
• Density of states