Transferring Electrochemical CO₂ Reduction from Semi‐Batch into Continuous Operation Mode Using Gas Diffusion Electrodes

Abstract

The electrochemical reduction of CO2 is a promising method for its conversion which still suffers from important challenges that have to be solved before industrial realization becomes attractive. The optimization of gas diffusion electrodes is described with respect to catalyst dispersion and mass transport limitations allowing solubility issues to be circumvented and current densities to be increased to industrially relevant values. The transfer of the promising results from semi‐batch experiments into continuous mode of operation is demonstrated, and it is indicated how the energetic efficiency can be significantly improved by the choice of electrolyte, in terms of concentration and type. Thereby ohmic losses can be decreased and the intrinsic activity be improved.

Influence of Temperature on the Performance of Gas Diffusion Electrodes in the CO2 Reduction Reaction

“…This leads to a theoretical catalyst loading of 2.55 wt‐% Sn, or 3.22 wt‐% SnO 2 . Electrodes were prepared as reported previously by mixing of the loaded carbon and PTFE (Dyneon, TF 92070Z, =4 μm) in a knife‐mill, followed by dry‐pressing in a cylindrical 7.1 cm 2 mask with 17.6 kN cm −2 for 30 min. Finally, the fragile raw electrodes were heated to 340 °C for 10 min (heat rate: 3.5 K min −1 ) under nitrogen atmosphere, resulting a GDE of sufficient mechanical stability.…”

“…This leads to a theoretical catalyst loading of 2.55 wt-% Sn, or 3.22 wt-% SnO 2 . Electrodes were prepared as reported previously [50] [6][7][8][9]14, red squares: values of our previous work; [7,[49][50][51] blue diamonds: this work.…”

“…SnO 2 was deposited on Acetylene Black by a homogeneous precipitation method based on the one previously reported. [50] Figure 4 shows the SEM and TEM images of the so prepared supported catalyst. SEM imaging shows a uniform distribution of SnO 2 nanoparticles on the support of about 10 nm to 40 nm in diameter.…”

“…[9,41,42,44,45,47,52] The highest reported current density reached with this configuration is 388 mA cm À 2 . [48] Previously, we reported the use of highly hydrophobic GDEs [49][50][51] known from alkaline fuel cell technology [53] or from oxygen-depolarized cathodes in the chlor-alkali synthesis. [54] The catalyst is thereby deposited homogenously on the porous carbon support, which is later mixed with PTFE (35 wt-%), pressed and heated, rendering the pore system highly hydrophobic.…”

Electrochemical Carbon Dioxide Splitting

“…The three‐compartment electrolyzers with flow gas and electrolytes (flow cell) are introduced to achieve high production rate in CO 2 electrolysis and have achieved exciting results recently. As shown in Figure d, a typical flow cell contains an extra gas compartment allowing the sufficient CO 2 supply to the cathode catalyst surface and thus obtains the higher current density compared to that of two‐compartment electrolyzers . Based on this flow cell electrolyzer, a new two‐compartment flow cell electrolyzer has been reported, which does not apply catholyte and corresponding compartment but cycles humid or dry CO 2 to obtained necessary proton from water in the humid gas supply .…”