Figure 1 a Large-scale scanning electron microscopy (SEM) image and 3D structure of CuO NS (insert, orange). b Transmission electron microscopy (TEM) image and c high resolution TEM (HR-TEM) images with measured lattice distance and the corresponding fast Fourier transformation. d Selected area electron diffraction (SAED) pattern along zone axis [001]. e 2D Synchrotron grazing incidence wide-angle X-ray scattering (GI-WAXS) image demonstrating preferred orientation of as-prepared CuO NS on glassy carbon. Additional azimuthally integrated line profiles are shown in Supplementary Fig. S5b.
Figure 2 a Absolute product formation rates of major gaseous products as a function of applied electrode potentials during CO2RR in CO2-saturated 0.1 M KHCO3 at 60 min. b Partial current densities as a function of applied electrode potentials during CO2RR in CO2-saturated 0.1 M KHCO3 at 60 min. c Chronoamperometric performance stability of the CO2 reduction reaction on CuO NS in CO2-saturated 0.1 M KHCO3 at −0.84 VRHE. d and e Long-term stability test over 60 h for d absolute product formation rates of major gaseous products and e Faradaic efficiencies on CuO NS in CO2-saturated 0.1 M KHCO3 at −1.0 VRHE. The error bars are given as standard error of mean. Catalyst loading: 100 μg cm−2.
Figure 3 In situ TEM imaging of catalyst structure during OCP in 30 µL/h H2O flow at a 2 s, b 50 s and c 110 s. The corresponding OCP profile is presented in Supplementary Fig. S15. The whole movie is shown as Supplementary Movie 1. d Current/potential profiles over time with marked time points, t1 - t4 (vertical lines), corresponding to the images in e–h. Linear sweep voltammetry (LSV) is performed after 10-second OCP measurement in a pH = 6.9 buffer solution flow (the OCP profile is given in Supplementary Fig. S17a) with scan rate of 50 mV/s. The following Chronoamperometry (CA) are acquired at −0.84 VRHE (the first potential). The whole movie is shown as Supplementary Movie 4. The corresponding images at i = 2.5 s and j = 460 s with the second LSV + CA (the 10-second OCP profile before LSV is given in Supplementary Fig. S17b) at −1.23 VRHE. Current/potential profiles over time with marked time points, - (vertical lines) and the images snapshots are shown in Supplementary Fig. S18. The whole movie is shown as Supplementary Movie 5. The corresponding images at k = 2.5and l =1000 s with the third LSV + CA (the 10-second OCP profile before LSV is given in Supplementary Fig. S17c) at −1.73 VRHE. Current/potential profiles over time with marked time points, - (vertical lines) and the images snapshots are shown in Supplementary Fig. S19. The whole movie is shown as Supplementary Movie 6. m Schematic overview (time line) of the experimentally observed evolution of the CuO NS morphology probed by the in situ TEM E-chip flow cell, H-cell, and flow cell electrolyzer.
Figure 4 a XANES at the Cu K-edge of the CuO NS catalysts at OCP in 0.1 M KHCO3 at pH 6.8 during 130 min CO2RR at −0.84 VRHE. b Linear combinations (with the weighting factors as fit parameters) of Cu foil and the CuO NS catalysts at OCP were fitted to experimental data of the CuO NS catalysts during 130 min CO2RR at −0.84 VRHE. Colored lines represent the experimental data and black lines the linear combinations. c Amount of Cu metal in the CuO NS catalysts during 130 min CO2RR at −0.84 VRHE. Values are obtained by linear combinations (with the weighting factors as fit parameters) of Cu foil and the CuO NS catalysts at OCP, which were fitted to experimental data. d FT of k3-weighted EXAFS at the Cu K-edge of the CuO NS film at OCP and during 130 min CO2RR at −0.84 VRHE in 0.1 M KHCO3 at pH 6.8. Colored lines represent the experimental data and black lines the simulations. The distance on the x-axis is reduced by 0.35 Å relative to the real internuclear distance. e EXAFS (k3 weighted) at the Cu K-edge of the CuO NS catalysts at OCP and during 130 min CO2RR at −0.84 VRHE in 0.1 M KHCO3 at pH 6.8. Colored lines represent the experimental data and black lines the simulations. Coordination numbers of the first Cu-O f coordination sphere and the first intermetallic Cu-Cu g shell (Details of the fit error and Fourier-filtered error can be found in the Supplementary Information). Catalyst loading: 100 μg cm−2.
XANESスペクトルはその横軸の変化が酸化状態、還元状態の変化を表し、またスペクトルの形状は結晶構造を反映しています。-0.84 V vs RHEを掃引した後、CuOは0価のCuに還元されていることが確認されました。おもしろい点は中間生成物としてCu2Oが形成されていないという点だと思います。実際にFig 4(a)のピンク色のスペクトル形状は時間経過のなかで出現していないようです。
a Operando differential electrochemical mass spectrometry (DEMS) sweep data obtained during CO2RR on CuO NS catalysts (supported on a flat 0.785 cm2 glassy carbon electrode, catalyst loading: 100 μg cm−2.) using CO2-saturated 0.1 M KHCO3 by continuous cyclic voltammetric scan at 5 mV s−1. b DEMS-derived mass charges for various products formed during the cathodic and anodic voltammetric sweep. The error bars are given as standard error of mean. c Spider plot shows the variations in the onset electrode potential of key products during CO2RR by continuous cyclic voltammetric scan at 5 mV s−1 (see Supplementary Table S2). Product molecules considered are: m/z = 28 CO, m/z = 15 corresponding to methane, m/z = 26 corresponding to ethylene, m/z = 31 corresponding to ethanol. d Faradaic efficiencies of CH4, EtOH and C2H4 on Cu(100) terraces of (from left to right) shrinking width and increasing density of Cu(110) steps. While Cu(100) shows little EtOH, EtOH increases with larger (110) step density and narrower (100) terrace width, peaking at Cu(310). The narrow (100) terraces on Cu(210) prevent EtOH formation in favor of CH4 (data from Ref. 56). e–g Illustration of *CH3 as common intermediate of CH4 and EtOH: Side views of the Cu(210), Cu(310) and Cu(510) single crystal facets. Cu(210) features exclusive *CH3 and *H adsorption toward CH4, while Cu(310) allows for C-C coupling between *CH3 and carbonaceous adsorbates on the (100) terraces toward EtOH. The wider (100) terraces of Cu(510) also enables C-C coupling among carbonaceous adsorbates to C2H4. Grey: C, white: H, red:O.
Morphology and mechanism of highly selective Cu(II) oxide nanosheet catalysts for carbon dioxide electroreduction Xingli Wang, Katharina Klingan, Malte Klingenhof, Tim Möller, Jorge Ferreira de Araújo, Isaac Martens, Alexander Bagger, Shan Jiang, Jan Rossmeisl, Holger Dau & Peter Strasser Nature Communications volume 12, Article number: 794 (2021)
