Electrochemical CO₂ Conversion Using Skeleton (Sponge) Type of Cu Catalysts

Abstract

Highly porous 3D Cu skeletons (sponges) modified by electropolishing, thermal annealing, and foam electrodeposition have been studied as catalysts for the electrochemical conversion of CO2 with a particular emphasis on C2 products formation. These catalyst materials appear to be promising for future applications where gaseous CO2 reactants can be transported through the 3D catalyst thereby tuning the mean residence time of reaction intermediates inside the catalyst, which crucially influences the final product distribution. In particular, the annealed skeleton (300 °C, 12 h) and the one modified by Cu foam electrodeposition show profound activities toward C2 product formation (C2H4, C2H6) with faradaic efficiencies reaching FEC2 = 32.3% (annealed skeleton sample, −1.1 V vs RHE) and FEC2 = 29.1% (electrodeposited sample, −1.1 V vs RHE), whereas the electropolished Cu skeleton remains largely inactive for both the C1 and the C2 pathway of hydrocarbon formation. This effect is discussed on the basis of residual impurities that are left behind from the investment casting approach on which the fabrication of these Cu skeleton support materials is based. In addition, a higher FEC2H4 /FEC2H6 ratio is observed for the annealed Cu skeleton as compared to the electrodeposited Cu foam. Such a switching in the C2 product distribution (FEC2H4 /FEC2H6 ratio) is discussed on the basis of particular morphological effects (residence time of intermediates inside the catalyst) related to the three-dimensional nature of the used catalysts.

Synthesis and Characterization of Degradation‐Resistant Cu@CuPd Nanowire Catalysts for the Efficient Production of Formate and CO from CO2

“…It should be noted that characteristic shakeup satellite features are expected for the Cu 2p3/2 emission in the range from BE = 939.3-945.6 eV when Cu(II) speacies (e. g. CuO) are present ( Figure S5). [51] Due to the low abundance of Cu(II) on the surface of the CuPd-NWs, the intensity of these shakeup satellite peaks is, however, within the noise level of this XPS spectrum and therefore not visible in this particular case.…”

“…In the third characteristic section of the FE vs E plot at E≤−1.0 vs RHE (Figure ) the parasitic HER starts to become the dominating cathodic reaction which goes along with the decrease of the FE CO values. Note, however, that this anti‐correlated trend in the FEs at high overpotentials/current densities favoring the HER is typically assigned to the onset of mass transport (diffusion) limitations of the dissolved CO 2 reactant in aqueous media when using a classical half‐cell measurement and do not necessarily indicate a failure of the catalyst itself . The solubility of CO 2 in aqueous media is limited to 35 mM …”

“…Similar to the Pd(II) species the copper oxide phases are also not stable under the cathodic conditions of CO 2 RR . We can therefore consider the actually active Cu@CuPd‐NW catalyst as ‘oxide/Pd(II)‐derived’ .…”

“…Similar to the Pd(II) species the copper oxide phases are also not stable under the cathodic conditions of CO 2 RR. [51] We can therefore consider the actually active Cu@CuPd-NW catalyst as 'oxide/Pd(II)-derived'. [3] Such CO 2 RR catalyst activation via the (electrochemical) reduction of a precursor compound has already been demonstrated as highly beneficial for the resulting performance and stability of CO 2 RR catalysts.…”

CO2 Reduction of Hybrid Cu2O–Cu/Gas Diffusion Layer Electrodes and their Integration in a Cu‐based Photoelectrocatalytic Cell

“…reported the CO 2 reduction on ordered porous Cu electrodes derived from Cu 2 O inverse opals, but these were not Cu–Cu 2 O hybrids and not supported on carbon materials. Similarly, Dutta et al . reported the behavior of Cu sponge‐type electrodes in CO 2 electrocatalytic conversion.…”