CeO2−δ as Electron Donor in Co0.07Ce0.93O2−δ Solid Solution Boosts Alkaline Water Splitting

Abstract Optimizing the electronic structure with increasing intrinsic stability is a usual method to enhance the catalysts’ performance. Herein, a series of cerium dioxide (CeO 2−δ ) based solid solution materials is synthesized via substituting Ce atoms with transition metal (Co, Cu, Ni, etc.), in which Co 0.07 Ce 0.93 O 2−δ shows optimized band structure because of electron transition in the reaction, namely Co 3+ (3d 6 4s 0 ) + Ce 3+ (4f 1 5d 0 6s 0 ) → Co 2+ (3d 7 4s 0 ) + Ce 4+ (4f 0 5d 0 6s 0 ), with more stable electronic configuration. The in situ Raman spectra show a stable F2g peak at ≈452 cm −1 of Co 0.07 Ce 0.93 O 2−δ , while the F2g peak in CeO 2−δ almost disappeared during HER progress, demonstrating the charge distribution of *H adsorbed on Co 0.07 Ce 0.93 O 2−δ is more stable than *H adsorbed on CeO 2−δ . Density functional theory calculations reveal that Co 0.07 Ce 0.93 O 2−δ solid solution increases protonation capacity and favors for formation of *H in alkaline media. General guidelines are formulated for optimizing adsorption capacity and the volcano plot demonstrates the excellent catalytic performance of Co 0.07 Ce 0.93 O 2−δ solid solution. The alkaline anion exchange membrane water electrolysis based on Co 0.07 Ce 0.93 O 2−δ /NiFe LDH realizes a current density of 1000 mA cm −2 at ≈1.86 V in alkaline seawater at 80 °C and exhibits long‐term stability for 450 h.