Physical characterization of POD-Cu. (A) XRD patterns of La₂CuO₄ electrodes after activation in Ar and CO₂-feed catholyte. The diffraction peaks marked by black rhombus originated from GDL substrate. The weak Cu diffraction in XRD pattern was the result of the very low content of Cu on the GDL (about 0.16 mg cm⁻¹). (B) Schematic diagram of the structural evolution of La₂CuO₄. (C) HAADF-STEM image and the corresponding EDX elemental mapping of POD-Cu. Scale bar: 100 nm. (D), (E) HR-TEM images of POD-Cu. Inset in (D) is the corresponding FFT pattern. Scale bars: 10 nm in (D) and 5 nm in (E). (F) Pb UPD profile of POD-Cu.