Density functional theory calculation of reaction pathways for AP decomposition over g-C3N4 surface

The profound understanding of decomposition mechanism of ammonium perchlorate (AP) is significant to the design of AP-based solid propellants. Herein, the possible decomposition reactions of AP over graphitic carbon nitride (g-C3N4) catalyst were investigated by employing density functional theory calculation to explore the reaction network of HClO4 and degradation pathway of NH3 on g-C3N4 surface. The energy barriers of elementary reactions in the network were obtained, the main reaction channels of the decomposition of HClO4 over g-C3N4 catalyst was found out to be HClO4 → ClO3- → ClO2- → ClO− → Cl−. The rate-limiting step along the pathway was the formation of ClO− from ClO2-, with the energy barrier as high as 1.903 eV. The oxidation of g-C3N4 surface would weaken the catalytic capacity of g-C3N4 for the decomposition of HClO4. However, the oxidation of g-C3N4 surface would enhance the catalytic capacity for the adsorption and dehydrogenation of NH3. The pre-adsorbed OH* on g-C3N4 surface would inhibit the adsorption of NH3 but it could promote the dehydrogenation of NH2* and NH*. This work provides new insights about the molecular-level decomposition mechanism of AP over g-C3N4.