In situ Dispersed Nano-Au on Zr-Suboxides as Active Cathode for Direct CO2 Electroreduction in Solid Oxide Electrolysis Cells

CO₂ electrochemical reduction in solid oxide electrolysis cells is an effective way to combine CO₂ conversion and renewable electricity storage. A Au layer is often used as a current collector, whereas Au nanoparticles are rarely used as a cathode because it is difficult to keep nanosized Au at high temperatures. Here we dispersed a Au layer into Au nanoparticles (down to 2 nm) at 800 °C by applying high voltages. A 75-fold decrease in the polarization resistance was observed, accompanied by a 38-fold improvement in the cell current density. Combining electronic microscopy, in situ near-ambient pressure X-ray photoelectron spectroscopy, and theoretical calculations, we found that the interface between the Au layer and the electrolyte (yttria-stabilized zirconia (YSZ)) was reconstructed into nano-Au/Zr-suboxide interfaces, which are active sites that show a much lower reaction activation energy than that of the Au/YSZ interface. The formation of Zr-suboxides promotes Au dispersion and Au nanoparticle stabilization due to the strong interaction between Au and Zr-suboxides.