Spin-State Tuning in PrFeO3-δ Perovskite Boosts High-Temperature Oxygen Evolution Reaction
Assoc. Prof. SONG Yuefeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. WANG Guoxiong from Fudan University, developed a series of alkaline-earth-metal-doped perovskites, Pr0.5Ae0.5FeO3-δ (Ae = Ca, Sr, Ba, labeled as PCF, PSF, PBF), to investigate the impact of electronic structure tuning on high-temperature OER performance.
Efficient energy conversion and storage technologies are critical for achieving China's carbon peak and carbon neutrality goals. Solid oxide electrolysis cells (SOECs) offer a promising route by converting renewable electricity into storable chemical fuels through high-temperature carbon dioxide electrolysis. However, the sluggish oxygen evolution reaction (OER) at the anode poses a major challenge due to its complex four-electron transfer process.Perovskite oxides are regarded as promising candidates for SOEC anodes due to their high mixed ionic–electronic conductivity and tunable electronic structures. Previous studies have revealed a volcano-shaped correlation between the occupancy of the 3d electron with eg symmetry in perovskite oxide and intrinsic OER activity in alkaline solution, with peak activity occurring at a near-unity eg occupancy. Yet, the intrinsic connection between eg occupancy and high-temperature OER activity has remained unclear due to the mechanistic differences between high- and low-temperature OER processes.Spin-state tuning in PrFeO3-δ perovskite for high-temperature oxygen evolution reaction (Image by YU Jingcheng)In a study published in Journal of the American Chemical Society, Assoc. Prof. SONG Yuefeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. WANG Guoxiong from Fudan University, developed a series of alkaline-earth-metal-doped perovskites, Pr0.5Ae0.5FeO3−δ (Ae = Ca, Sr, Ba, labeled as PCF, PSF, PBF), to investigate the impact of electronic structure tuning on high-temperature OER performance.Researchers found that OER activity increases with larger dopant ionic radius, and PBF achieves a current density of 3.33 A cm−2 at 2.0 V and 800 °C. Detailed analyses revealed that alkaline earth metal doping enhances Fe 3d-O 2p hybridization, lowers charge-transfer energy, and promotes oxygen ions migration and surface spillover, thereby accelerating the OER process. Moreover, magnetic measurements showed that Ba doping induces a spin-state transition from high-spin Fe3+ (t2g3eg2) to low-spin Fe4+ (t2g4eg0), resulting in reduced eg occupancy and accelerated oxygen kinetics."Our study establishes spin-state tuning as a key strategy to boost high-temperature OER activity and provides fundamental guidance for electronic structure engineering in the design of advanced SOEC anode materials," said Dr. SONG.