Atomic layer deposition of alumina on hollow nickel phyllosilicate nanosheets for enhanced CO2 thermal hydrogenation performance

Abstract

Herein, NiSiO3@Al2O3 catalysts were prepared by encapsulating Al2O3 films on nickel phyllosilicate nanosheets via atomic layer deposition (ALD) technique, and used for CO2 hydrogenation reaction. The NiSiO3-R600 catalyst without Al2O3 films underwent serious agglomeration of Ni particles after H2 reduction at 600 °C, leading to poor CO2 conversion of 22.6%. In comparison, CO2 conversion over NiSiO3@5Al2O3-R600 catalyst reached 66.9% due to that the ALD-Al2O3 film can effectively alleviate the agglomeration of Ni particles (6.3 vs. 22.1 nm). Furthermore, the electronic interaction between Al2O3 and the metallic nickel site was confirmed by both XPS spectroscopy and DFT calculations. The chemisorption behaviors of probe molecules on the catalyst surface also prove the better dispersion of metallic Ni sites in the presence of the ALD-Al2O3 layer. Moreover, in-situ DRIFTS characterization indicates that the presence of ALD-Al2O3 film promoted the hydrogenation of HCOO* to CH3O*, which then increased the CO2 conversion and CH4 selectivity.