Boosting N₂O Decomposition by Fabricating the Cs–O–Co Structure over Co₃O₄ with Single-Layer Atoms of Cs

Abstract

Developing effective catalysts for N 2 O decomposition at low temperatures is challenging. Herein, the Cs−O−Co structure, as the active species fabricated by single-layer atoms of Cs over pure Co 3 O 4 , originally exhibited great catalytic activity of N 2 O decomposition in simulated vehicle exhaust and flue gas from nitric acid plants. A similar catalytic performance was also observed for Na, K, and Rb alkali metals over Co 3 O 4 catalysts for N 2 O decomposition, illustrating the prevalence of alkali-metal-promotion over Co 3 O 4 in practical applications. The catalytic results indicated that the TOF of Co 3 O 4 catalysts loaded by 4 wt% Cs was nearly 2 orders of magnitude higher than that of pure Co 3 O 4 catalysts at 300 °C. Interestingly, the conversions of N 2 O decomposition over Co 3 O 4 catalysts doped by the same Cs loadings were significantly inhibited. Characterization results indicated that the primary active Cs−O−Co structure was formed by highly orbital hybridization between the Cs 6s and the O 2p orbital over the supported Co 3 O 4 catalysts, where Cs could donate electrons to Co 3+ and produce much more Co 2+ . In contrast, the doped Co 3 O 4 catalysts were dominated by Cs 2 O 2 species; meanwhile, CsOH species was generated by adsorbed water vapor led to a significant decrease in catalytic activity. In situ DRIFTS, rigorous kinetics, and DFT results elaborated the reaction mechanism of N 2 O decomposition, where the direct decomposition of adsorbed N 2 O was the kinetically relevant step over supported catalysts in the absence of O 2 . Meanwhile, the assistance of adsorbed N 2 O decomposition by activated oxygen was observed as the kinetically relevant step in the presence of O 2 . The results may pave a promising path toward developing alkali-metal-promotion catalysts for efficient N 2 O decomposition.