Interfacial CN-layer engineering boosts Mn active sites in MoO₂/MnO₂ heterostructure for efficient and durable acidic...

The development of efficient and stable electrocatalysts for the oxygen evolution reaction (OER) in acidic media remains a critical challenge. Here, we designed a hierarchical structure catalyst comprises of MnO₂ and carbon‑nitrogen compound (CN) coated MoO₂ (denoted as MoO₂@CN/MnO₂), in which the Mn species is identified as the real active site for OER and the Mo-containing species (MoO₂@CN) serves as the promoter. The incorporation of CN into the interface between the MoO₂ and MoO₂ facilitates the inner electron transfer from Mo to Mn, thereby increasing the quantity of Mn³⁺ active sites for more efficient OER process, and at the meantime, the presence of CN effectively suppresses Mn dissolution during OER, stabilizing these active sites and improving the overall catalytic stability. The MoO₂@CN/MnO₂ heterostructure exhibits decreases of 29 mV and 74 mV for the overpotential at 20 mA cm^-2 compared with the MoO₂/MnO₂ and the MnO₂, and shows enhanced electrocatalytic stability. This work provides a promising and facile strategy for enriching and stabilizing the active species for acidic OER catalysts.