Bi‑functional extension on heterogeneous ORR/OER catalysis with 2D materials for Li‑O2 batteries

As the global demand for high-energy-density storage systems continues to surge, conventional lithium-ion batteries face fundamental limitations in theoretical capacity and energy density. Now, researchers from Shandong University, led by Professor Feng Dang, Professor Guoliang Zhang, Professor Han Yu, and their collaborators from Shandong Normal University, Hainan University, and Northumbria University, have presented a comprehensive review on how two-dimensional (2D) materials are revolutionizing lithium–oxygen battery (LOB) technology through heterogeneous ORR/OER catalysis.

Why 2D Materials Matter

Traditional cathode catalysts in LOBs typically suffer from sluggish oxygen reduction/evolution reaction (ORR/OER) kinetics, high overpotentials, and poor cycling stability. The unique anisotropy and electronic properties of 2D materials—graphene, transition metal oxides/hydroxides, MXenes, and dichalcogenides—overcome these limitations by providing atomically thin platforms with large surface areas, abundant exposed active sites, and tunable electronic structures that simultaneously activate both discharge and charge processes.

Innovative Design and Mechanism

The review systematically categorizes activation engineering strategies spanning point, line, plane, and bulk dimensions. At the atomic scale, vacancies and heteroatomic doping modulate local electronic states and reactant adsorption. At the nanoscale, interface structures and crystal plane orientation tune the d-band center and optimize intermediate binding strength. At the macroscale, morphology regulation and heterostructure construction create synergistic electronic compensation through built-in electric fields. Monte Carlo simulations and DFT calculations reveal that the exceptional performance originates from precise control over LiO₂ adsorption energy—neither too strong nor too weak—enabling reversible Li₂O₂ formation and decomposition with minimal overpotential.

Outstanding Performance

The reviewed 2D catalysts deliver remarkable metrics: vertical graphene achieves 23,864 mAh g^-1 with 0.45 V charge overpotential; CoN₃ single-atom catalysts maintain 0.51 V overpotential even after 3,500 hours; Mn₃O₄/graphene composites reach 35,583 mAh g^-1; and Ti_0.87O₂/MXene heterostructures sustain 2,500 hours of stable cycling. The 1T/2H MoS₂ phase-engineered catalysts and Ag-intercalated SnSe₂ systems demonstrate how anisotropic catalytic properties can be harnessed to direct selective Li₂O₂ growth pathways, fundamentally altering reaction mechanisms from solution-mediated to surface-mediated processes.

Applications and Future Outlook

Beyond cathode catalysis, 2D materials extend their functionality across the entire LOB system: graphene and h-BN coatings suppress lithium dendrite growth with mechanical strengths exceeding 1.0 TPa; MXene-modified separators block redox mediator shuttling while homogenizing Li⁺ flux; and phosphorene-derived SEI layers enable stable cycling over 500 cycles. When integrated with machine learning-guided electrolyte optimization and in situ characterization techniques (Raman, DEMS, XAS), these materials pave the way for practical Li–air batteries operating in ambient conditions.

This work establishes a unified mechanistic framework connecting electronic structure, intermediate adsorption, and electrochemical performance, opening promising avenues for next-generation energy storage systems combining ultrahigh energy density, fast charging, and long-term stability.

Stay tuned for more groundbreaking research from this collaborative team at Shandong University and their international partners!