Lattice oxygen activation in disordered rocksalts for boosting oxygen evolution

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Oxygen evolution reaction (OER) electrocatalysts face limitations due to the scaling relationship in conventional adsorbate evolution mechanisms.
• Lattice oxygen participation via the lattice oxygen oxidation mechanism (LOM) offers a new avenue for catalyst design.

Purpose of the Study:

• To theoretically predict and experimentally validate lithium-excess disordered rocksalts (DRX) as OER electrocatalysts operating via the LOM pathway.
• To explore novel electrocatalyst materials that circumvent the conventional OER scaling relationship.

Main Methods:

• Theoretical prediction of DRX properties, focusing on O-Li orbital interactions and Li-O-Li ligands.
• Isotope labeling experiments to confirm lattice oxygen involvement in the OER process.
• Electrochemical testing of Li_1.2Fe_0.4Ti_0.5O₂ for OER activity, pH dependence, overpotential, and stability.

Main Results:

• DRX materials demonstrate facile activation and oxidation of lattice oxygen at high voltages.
• Isotope labeling confirms lattice oxygen participation in OER through the LOM pathway.
• Li_1.2Fe_0.4Ti_0.5O₂ exhibits pH-dependent OER activity, a low overpotential (263 mV at 10 mA cm^-2), and 100-hour stability.
• The turnover frequency of Li_1.2Fe_0.4Ti_0.5O₂ is significantly higher (9x) than LiFePO₄ at 300 mV overpotential.

Conclusions:

• Lithium-excess disordered rocksalts are promising OER electrocatalysts utilizing the LOM pathway.
• This research opens new possibilities for designing efficient electrocatalysts by exploring DRX materials.
• The LOM pathway in DRX offers a strategy to overcome the OER scaling relationship, advancing catalyst performance.