N-Doped-Induced Local Covalency Elevation for Enhancing Cathodic Performance of Solid Oxide Electrolysis Cells

The Ni-based cathode is central to the performances of solid oxide electrolysis cells (SOECs), yet it suffers from poor oxygen ion conductivity, sluggish electron transport, and inefficient CO2/H2O activation. This study explores a heteroatom-doping strategy to comprehensively address the ionic, electronic, and molecular issues in solid oxide cells. When operated in SOEC mode, the maximum power density of the N-doped Ni/CGO (NiO/CGON) cathode achieved a 29.6% improvement over its undoped Ni/CGO, along with a 27.3% reduction in polarization resistance. Moreover, a 31.3% increase in maximum current density was obtained along with considerable stable operation over 150 h at an industrial-scale current density of 0.5 A/cm2. Combined electrochemical measurements, in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and density functional theory (DFT) simulations reveal that N-doped-induced local covalency elevation via the formation of Ce–O/N bonds substantially promotes the oxygen ion and electron conductivity and creates the synergistic Lewis acid–base sites for simultaneous activation of both CO2 and H2O, thereby collectively addressing the ionic, electronic, and molecular issues in SOCs in one simple method.