Iron phthalocyanine derived Fe1/h-BN single atom catalysts for CO2 hydrogenation

Abstract

Iron phthalocyanine-coated hexagonal boron nitride (FePc/h-BN) nanoparticles, obtained by FePcCl adsorption on the h-BN surface from a dimethylformamide solution, were subjected to heat treatment in order to form single atom Fe₁/h-BN catalysts. Samples were characterized by means of X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy, and temperature-programmed oxidation/reduction/desorption. The FePc deposition process was optimized to avoid the formation of nanoparticles. FePc exhibits high thermal stability in a hydrogen atmosphere and decomposes into a single iron atom when oxidizing in an O₂ flow at 350 °C (sample Fe₁-ox/h-BN). Subsequent reductive heat treatment in hydrogen (sample Fe₁-red/h-BN) results in the formation of Fe-based nanoparticles due to Fe₁ diffusion and association, resulting in a decrease in catalytic activity. Hydrogenation proceeds according to the Eley–Rideal mechanism with CO₂ chemisorption on the Fe₁ surface species (Fe₁-ox/h-BN) and is changed to the Langmuir–Hinshelwood mechanism (Fe₁-red/h-BN). Selectivity for hydrocarbons increases after reduction of the Fe₁-ox/h-BN sample. Our results open up new possibilities for using metal phthalocyanine as a precursor for cheap, reproducible, and efficient single atom catalysts for CO₂ hydrogenation.