Issue 22, 2020

Cu/M:ZnO (M = Mg, Al, Cu) colloidal nanocatalysts for the solution hydrogenation of carbon dioxide to methanol

Abstract

Doped-ZnO nanoparticles, capped with dioctylphosphinate ligands, are synthesised by the controlled hydrolysis of a mixture of organometallic precursors. Substitutional doping of the wurtzite ZnO nanoparticles with 5 mol% Mg(II), Al(III) and Cu(I) is achieved by the addition of sub-stoichiometric amounts of the appropriate dopant [(n-butyl)(sec-butyl)magnesium, triethylaluminium or mesitylcopper] to diethylzinc in the precursor mixture. After hydrolysis, the resulting colloidal nanoparticles (sizes of 2–3 nm) are characterised by powder X-ray crystallography, transmission electron microscopy, inductively-coupled plasma optical emission spectrometry and X-ray photoelectron spectroscopy. A solution of the doped-ZnO nanoparticles and colloidal Cu(0) nanoparticles [M:ZnO : Cu = 1 : 1] are applied as catalysts for the hydrogenation of CO2 to methanol in a liquid-phase continuous flow stirred tank reactor [210 °C, 50 bar, CO2 : H2 = 1 : 3, 150 mL min−1, mesitylene, 20 h]. All the catalyst systems display higher rates of methanol production and better stability than a benchmark heterogeneous catalyst, Cu–ZnO–Al2O3 [480 μmol mmolmetal−1 h−1], with approximately twice the activity for the Al(III)-doped nanocatalyst. Despite outperforming the benchmark catalyst, Mg(II) doping is detrimental towards methanol production in comparison to undoped ZnO. X-Ray photoelectron spectroscopy and transmission electron microscopy analysis of the most active post-catalysis samples implicate the migration of Al(III) to the catalyst surface, and this surface enrichment is proposed to facilitate stabilisation of the catalytic ZnO/Cu interfaces.

Graphical abstract: Cu/M:ZnO (M = Mg, Al, Cu) colloidal nanocatalysts for the solution hydrogenation of carbon dioxide to methanol

Supplementary files

Article information

Article type
Paper
Submitted
13 Phe 2020
Accepted
15 Mot 2020
First published
27 Mot 2020

J. Mater. Chem. A, 2020,8, 11282-11291

Cu/M:ZnO (M = Mg, Al, Cu) colloidal nanocatalysts for the solution hydrogenation of carbon dioxide to methanol

A. H. M. Leung, A. García-Trenco, A. Phanopoulos, A. Regoutz, M. E. Schuster, S. D. Pike, M. S. P. Shaffer and C. K. Williams, J. Mater. Chem. A, 2020, 8, 11282 DOI: 10.1039/D0TA00509F

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