Theoretical Prediction of the N−H and O−H Bonds Cleavage Catalyzed by the Single-Walled Silicon Carbide Nanotube

Abstract

Effective cleavage of the N−H and O−H bonds at “metal-free” centers has attracted considerable attention due to the fundamental and industrial importance. In this paper, we show by density functional theory calculations that the pure silicon carbide nanotube (SiCNT) can effectively cleave the N−H bond of ammonia and the O−H bond of H−OX (X = H, CH3, and C2H5). Both the N−H and O−H bond cleavage undergoes two evolution steps: (i) molecular chemisorption of NH3 or H−OX followed by (ii) the activated N−H bond of NH3 or O−H cleavage of H−OX. For the N−H bond cleavage of ammonia, the adsorption energy (−1.199 eV) and the subsequent H-transfer barrier (0.842 eV) from the Si atom to the neighboring C atom indicate a zero total N−H splitting barrier by the Si+−C− center of SiCNT. Similarly, the SiCNT can also split the O−H bonds of H−OX with a considerably larger exothermicity (ca. −1.800 eV) than that of the N−H bond cleavage (−1.370 eV). Subsequently, the resulting NH2 or OX groups and H atom can be converted t...