Synthesis and spectroscopic characterisation of aurichalcite (Zn,Cu2+)5(CO3)2(OH)6; implications for Cu–ZnO catalyst precursors

Abstract

The Cu-ZnO catalyst precursors with variable Cu:Zn ratio, between Zn-rich and Cu-rich compositions have been investigated by a combination of electronic and vibrational spectroscopy. Synthesized catalyst precursors exhibit two d-d transition bands of Cu 2+ ions in a distorted octahedral symmetry, at 7,600 and 12,900 cm -1 (1,315 and 775 nm). The effect of structural cation substitution (Zn 2+ and Cu 2+ ) on band shifts is observed in the spectra of the synthetic catalyst precursors. The observation of two broad features at *7,600 and 12,900 cm -1 (1,315 and 775 nm) is a strong indication for Zn 2+ substitution by Cu 2+ ions. The result of multiple bands in the symmetric stretching and bending regions confirms the reduction of symmetry from D 3h to C 2v /C s for (CO 3 ) 2-ion in aurichalcite. The synthetic aurichalcite may be used as a standard for identification of spectral properties of naturally occurring anhydrous carbonate minerals.

Cu,Zn-based catalysts for methanol synthesis: On the effect of calcination conditions and the part of residual carbonates

“…In that matter we neglect the influence of adsorbed CO 2 due to exposure to air on the relevant band regions. The four strong bands observed in AU precursor at 1558, 1507, 1406 and 1366 cm -1 (see Figure 5a), corresponding to the asymmetric C-O stretching mode ν 3 of carbonate, agreed very well with the data published in the literature [5,25,29]. In the calcined AU sample series 4 bands could still be recognized.…”

“…In the calcined AU sample series 4 bands could still be recognized. The large number of bands in the carbonate asymmetric stretching vibration region can be related to the 4 differently coordinated metal centers (octahedral, tetragonally elongated, tetrahedral and trigonal bipyramidal) present in the aurichalcite structure and to the symmetry reduction of the coordinated carbonate compared to the free carbonate ion (see also Figure 6 for comparison) [29]. Additionally, the splitting of the ν 3 band observed for AU indicates a symmetry reduction of the carbonate.…”

The fabrication and characterization of Zn 5 (CO 3 ) 2 (OH) 6 as a new anode material for lithium ion batteries

“…As one of the main sort of zinc mineral in natural, zinc carbonate hydroxide, Zn 5 (CO 3 ) 2 (OH) 6 has been widely adopted as an active precursor for the preparation of ZnO 2 and ZnO [1][2][3][4]. Meanwhile, the partial substitution of zinc in Zn 5 (CO 3 ) 2 (OH) 6 by other metal element such as copper can lead to the formation of other (Zn x M 1-x ) 5 (CO 3 ) 2 (OH) 6 composites (M ¼Cu, etc.…”

Thermokinetic investigation of binary Cu/Zn hydroxycarbonates as precursors for Cu/ZnO catalysts

“…At the same time, the number of publications focusing on the description of the decomposition process and the influence of calcination conditions on the catalytic activity is quite limited [8,9,10,11]. Some studies [12,13] deal with the characterization of binary precursors for Cu/ZnO catalysts, which serve as a suitable model for technical ternary Cu/ZnO/Al 2 O 3 systems.…”