Single-phase gadolinium-doped ceria cathode for highly efficient CO 2 electrolysis

High-temperature solid-oxide CO2 electrolysers enable high-efficiency conversion of electrical energy to valuable fuels and chemicals and as such facilitate a sustainable-energy technology. Conventional cermet-based fuel electrodes used in such solid-oxide...


Fig. S2
] Fig. S3 Arrhenius plot and oxygen partial pressure dependence of (a, b), ion transfer resistance ( int ) and (c, d) effective capacitance ( int ).Data obtained from equivalent circuit fitting of impedance spectra of symmetrical cells, GCO | 8YSZ | GCO, recorded (a, c) at different temperatures in CO2/CO 50/50 and (b, d) at 750 °C in different CO2/CO gas mixtures.S3).The parameter  exp represents the experimentally applied electrode thickness.Corresponding data obtained from fitting are listed in Table S6.al. 4 The electronic conductivity of GCO is calculated using σ eon = σ eon 0 O 2  .Values of σ eon 0 and  obtained from fitting experimental data of the total conductivity (Fig. 6) are listed in Table S5.The linear relationship between both parameters reflects a constant mobility of the electronic charge carriers within the experimental range.The dashed straight line is from linear regression analysis of the data.

Fig. S4
Fig. S4 Arrhenius plot and oxygen partial pressure dependence of (a, b) surface reaction resistance ( react ) and (c, d) effective capacitance ( react ).Data obtained from equivalent circuit fitting of impedance spectra of symmetrical cells, GCO | 8YSZ | GCO, recorded (a, c) at different temperatures in CO2/CO 50/50 and (b, d) at 750 °C in different CO2/CO gas mixtures.The dashed lines serve as guides for the eye.

Fig. S5
Fig. S5 Comparison of electron carrier concentrations [Ce Ce′ ] at 750 °C determined from the oxygen partial pressure-dependent capacitance data (shown in Fig.S4c) using eqn (2) with corresponding values calculated from data of oxygen non-stoichiometry of GCO reported by Bishop et al.1

Fig. S6
Fig. S6  TLM | →0 as a function of GCO electrode thickness, showing an optimal electrode thickness ( opt ) at around 32 µm.Values of  TLM | →0 were calculated after thickness-dependent scaling of the resistance values  ion ,  eon and  react determined at 750 °C in CO2/CO 50/50 (listed in TableS3).The parameter  exp represents the experimentally applied electrode thickness.

Fig. S8
Fig. S8 Correlation between electron carrier concentration [Ce Ce ′ ] and electronic conductivity at 750 °C.Data of [Ce Ce ′ ] were calculated from oxygen non-stoichiometry data of GCO reported by Bishop et

Table S1 .
Electrode parameters and equations for estimating values of  ion and  eon used for fitting of data of impedance spectroscopy.Conductivity and resistance values are specified for 750 °C.

Table S2 .
Best-fit parameters obtained from equivalent circuit fitting of the impedance spectrum shown in Fig.3a.

Table S3 .
Resistance values obtained from fitting impedance spectra of symmetrical cells GCO | 8YSZ | GCO recorded at 750 °C in different CO2/CO gas mixtures.

Table S4 .
Resistance values obtained from fitting impedance spectra of symmetrical cells GCO | 8YSZ | GCO recorded at different temperatures in CO2/CO 50/50.