Enabling pure CO2 reduction on Ni-YSZ electrodes: Operando studies indicate an oxide-mediated mechanism

Abstract

Ni-YSZ-based electrodes are well-established in the field of solid oxide technologies. Ni/YSZ-based architectures have well-known performance and mechanical properties besides well-established manufacturing processes. Solid oxide-based CO2 electrolysis on Ni-YSZ at high temperature requires the presence of H2 in the CO2 inlet stream. It is believed that in pure CO2 streams the reaction fails due to oxidation of the Ni-YSZ electrode. Using operando Raman spectroscopy and online mass spectroscopy, we have shown that CO2 can in fact be reduced on the Ni-YSZ surface. Our measurements, reveal that Ni-YSZ oxidizes to NiOx-YSZ within a pure CO2 stream. CO2 electrolysis is possible on this oxide surface via a surface oxygen and vacancy-mediated mechanism similar to those observed within other oxide cathodes such as CeOx. The deactivation of the electrode coincides with strongly reducing conditions and at current densities > 400 mA/cm2, NiOx is completely reduced coinciding with complete stoppage of CO production. Cu-impregnation into Ni-YSZ was demonstrated to mitigate the deactivation issue by forming a more stable surface oxide on Ni which continued to carry out CO2 reduction under strongly reducing conditions. The new electrode demonstrated improved kinetics and stability against carbon deposition via Bouduard reaction.

Enhancement in CO2 Electroreduction upon Pr Infiltration of Ceria Electrodes

“…The oxide ions are conducted away to the anodic side where O2 evolves. 14,18,32 https://doi.org/10.26434/chemrxiv-2024-swljj ORCID: https://orcid.org/0000-0002-3758-3751 Content not peer-reviewed by ChemRxiv. License: CC BY-NC-ND 4.0 CO2 reduction requires Ce 3+ sites.…”

“…spectroscopy at 800 o C. 18 A Raman microscope (Renishaw) equipped with 532 nm laser was used to record operando Raman signals. Materials were characterized using scanning electron microscopy (SEM, EDX), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and Raman spectroscopy.…”

Cu infiltrated Ni-YSZ cathode in CO2 (+H2) stream: Reverse Water Gas Shift vs. CO2 electrolysis

“…22 Raman spectra of B, C, and D show peaks at 534 and 1074 cm -1 , indicating the presence of Cu-doped Ni oxide (Cu alloyed into Ni oxide). [23][24][25][26] Spectrum at E (black spot) on Ni{Cu}Ox-YSZ surface shows peaks at 294, 342, and 622 cm −1 corresponding to Ag, Bg, and Bg vibrational modes of CuO. 27…”