Preparation of carbon nanotube-filled bismuth/tin green nanocomposites and their efficient catalytic activity in the thermal decomposition of ammonium perchlorate

The practical utility of bismuth and tin compounds, as promising green combustion catalysts, is constrained by their substantial particle agglomeration. Herein, a straightforward ultrasonication-assisted method was reported to incorporate bismuth and tin compounds into the inner spaces of carbon nanotubes (CNTs), affording CNTs-confined bismuth (tin) compounds. The as-prepared nanocomposites were structurally completely characterized. The electrochemical property investigations showed that the introduction of bismuth and tin compounds increases the catalytic active sites of carbon nanotubes and inhibits nanoparticle agglomeration effectively. The theoretical calculations revealed that synergistic effects between Bi2O3 and carbon nanotubes can improve the efficiency of electron transfer in the Bi(NO3)3@A-CNTs(M1) composite. The evaluation results of the combustion catalytic performance of the nanocomposites on ammonium perchlorate (AP) pyrolysis suggested that adding 5 wt.% Bi(NO3)3@A-CNTs(M1) and DBT@A-CNTs(M1) (DBT = Dibutyltin dichloride) in AP brought about a more concentrated thermal decomposition process, advancing the peak of AP in the high-temperature decomposition stage from 420.4 ℃ to 328.9 and 325.9 ℃, respectively, and boosting its heat release from 976.42 J·g−1 to 2251.2 J·g−1 and 2452.03 J·g−1, respectively. The studies on the thermal degradation mechanism of AP, probed by thermal decomposition kinetics, in-situ solid FTIR and TG-FTIR-MS, concluded that the electron transfer from the critical steps ClO4− to NH4+ and O2 to O2− is accelerated by the interaction of the in-situ formed Bi2O3 nanoparticles and carbon nanotubes, boosting the relative contents of more stable gases, and ultimately promoting AP pyrolysis. A tentative catalytic thermal degradation mechanism of AP is finally proposed.