Catalytic decomposition of NO using molten gallium: an experimental and computational study

Molten gallium (Ga) catalyzes the direct decomposition of NO. In a bubble column reactor, NO decomposition was conducted by injecting NO-containing bubbles into molten Ga at elevated temperatures (> 400 °C), and > 90% conversion was achieved in only ∼ 0.2 s of residence time at 550 °C. Computational analysis showed that despite the weak binding energy of NO to Ga surface (34.4 kJ/mol), thermodynamically favored NO* dissociation on Ga (−138.3 kJ/mol) facilitated decomposition. Although Ga surfaces can be poisoned by O* generated by the dissociation of NO*, introducing reduction gas promoted OH* formation (−51.1 kJ/mol) on the surface and subsequent H₂O desorption, and consequently reactivated the Ga surface. NO decomposition and catalyst regeneration using reducing gas was repeated over 15 cycles in a single droplet reactor, and NO conversion was stably maintained. Experimental and computational results support the potential use of molten Ga as a catalyst for the direct decomposition of NO.