CeO_2-δ as Electron Donor in Co_0.07Ce_0.93O_2-δ Solid Solution Boosts Alkaline Water Splitting

Area of Science:

• Materials Science
• Catalysis
• Electrochemistry

Background:

• Optimizing catalyst electronic structure and stability is crucial for enhancing catalytic performance.
• Cerium dioxide (CeO_2-δ) is a promising material, but its intrinsic properties often require modification for advanced applications.
• Transition metal doping offers a viable strategy to tune the electronic and structural characteristics of cerium dioxide.

Purpose of the Study:

• To synthesize and characterize novel cerium dioxide-based solid solutions doped with transition metals.
• To investigate the electronic structure modifications induced by cobalt doping in cerium dioxide.
• To evaluate the catalytic performance of the synthesized materials for hydrogen evolution reactions in alkaline media.

Main Methods:

• Solid-state synthesis of Co_xCe_1-xO_2-δ solid solutions.
• In situ Raman spectroscopy to study reaction intermediates and stability.
• Density functional theory (DFT) calculations to analyze electronic structure and adsorption properties.
• Electrochemical testing, including alkaline anion exchange membrane water electrolysis.

Main Results:

• Co_0.07Ce_0.93O_2-δ exhibits an optimized band structure due to a stable electron transition (Co³⁺ + Ce³⁺ → Co²⁺ + Ce⁴⁺).
• In situ Raman spectra confirm enhanced stability of adsorbed hydrogen (*H) on Co_0.07Ce_0.93O_2-δ compared to pristine CeO_2-δ.
• DFT calculations indicate increased protonation capacity and favorable *H formation on Co_0.07Ce_0.93O_2-δ in alkaline media.
• The Co_0.07Ce_0.93O_2-δ/NiFe LDH electrode achieved 1000 mA cm^-2 at 1.86 V in alkaline seawater at 80 °C, with 450 h of stable operation.

Conclusions:

• Cobalt doping effectively optimizes the electronic structure and intrinsic stability of cerium dioxide for catalysis.
• The Co_0.07Ce_0.93O_2-δ solid solution demonstrates superior performance in alkaline hydrogen evolution reactions.
• This material shows significant potential for efficient and durable alkaline seawater electrolysis applications.