Direct conversion of methane into methanol and ethanol via spherical Au@Cs_2[closo-B_(12)H_(12)]and Pd@Cs_2[closo-B_(12)H_(12)] nanoparticles

摘要

In this present study, novel aqueous-phase catalytic systems, namely spherical Au and Pd nanoparticles (NPs) capped with Cs-2 [closo-B12H12], were used to produce ethanol and methanol via direct oxidation of methane in the presence of H2O2 and O-2 under mild conditions. The ethanol selectivity surpassed 52.96% and 86.33% at 50 degrees C, and the productivity reached 8.86 and 25.18 mol.kgcat(-1).h(-1), respectively. Plausible methane-ethane-ethanol pathway involving free radial center dot OH radicals was proposed based on the electron paramagnetic resonance (EPR) result. According to the theoretical calculations, the surfaces of {111} plane of Au NPs and {100} plane of Pd NPs were capped with Cs-2 [closo-B12H12], and Au-B and Pd-B bonds were consequently formed, respectively. Moreover, the binding energies of Au NPs and Pd NPs capped with Cs-2 [closo-B12H12] were calculated to be -128.9 and -230.1 kcal mol(-1), respectively. Based on the theoretical calculations, higher binding energy indicates a larger amount of charge on the surfaces of the planes of NPs. A lower peak intensity can lead to the formation of a more stable catalyst with enhanced catalytic activity. Thus, the ethanol selectivity of the as-prepared catalyst was considerably higher than that for methanol. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.