Stable Cu Catalysts Supported by Two-dimensional SiO2 with Strong Metal-Support Interaction

Abstract

Cu-based catalysts exhibit excellent performance in hydrogenation reactions. However, the poor stability of Cu catalysts under high temperatures has restricted their practical applications. The preparation of stable Cu catalysts supported by SiO₂ with strong metal-support interaction (SMSI) has thus aroused great interest due to the high abundance, low toxicity, feasible processability, and low cost of SiO₂ . The challenge in the construction of such SMSI remains to be the inertness of SiO₂ . Herein, a simple and scalable method is developed to prepare 2D silica (2DSiO₂ ) supported Cu catalysts with SMSI by carefully manipulating the topological exfoliation of CaSi₂ with CuCl₂ and thereafter calcination. The prepared Cu-2DSiO₂ catalysts with the unique encapsulated Cu nanoparticles exhibit excellent activity and long-term stability in high-temperature CO₂ hydrogenation reactions. This feasible and low-cost solution for stabilizing Cu catalysts might shed light on their realistic applications.

Keywords: Cu/SiO2; high-temperature stability; strong metal-support interaction (SMSI)FF.

Figure 1

a) Schematic of the synthesis process of Cu‐2DSiO₂ based catalysts. The blue sheet, the white sheet, the red nanoparticles, and the cyan shell around red particles are composed of Si, Ca, Cu, and Cu⁺, respectively. b) SEM image, and c) TEM image of 2DSi supported large Cu nanoparticles. d) TEM image, and e–h) EDS mappings of 2DSiO₂ supported large Cu nanoparticles after calcination. i) TEM image, and j–m) EDS mappings of Cu‐2DSiO₂‐400_r.

Figure 2

Catalytic performance of CO₂ hydrogenation (mass of the catalyst: 50 mg; reaction temperature: 500 ℃; flow rates of the reactants: CO₂/H₂/N₂ = 5/5/5 mL min^‐1). a) CO₂ conversion after 54 h testing, and CO selectivity. The hollow column in (a) represents the thermodynamical equilibrium CO₂ conversion for reverse water‐gas shift reaction at 500 ℃ when the flow rate of CO₂ equals that of H₂. b) Arrhenius plot fitting from the CO rates (Table S2, Supporting Information). c) CO₂ conversion under 500 ℃ during a 54 h test for the different Cu catalysts.

Figure 3

a) Cu LMM XAES spectra, b) Raman spectra, c) Cu K‐edge XANES spectra, d) the Fourier transform curves of the EXAFS spectra at the Cu K‐edge, e) diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) spectra of CO adsorbed at room temperature and f) temperature‐programmed reduction (TPR) profiles of different Cu catalysts.

Figure 4

Schematic illustration of the possible evolution routes of different Cu catalysts during preparation and prolonged reaction.