High-Dimensional MoO_x Promotes Meta-Stable Mo⁵⁺ Active Site Regeneration for Efficient H₂O₂ Electrosynthesis

Electrocatalytic two-electron oxygen reduction reaction (2e^- ORR) is a green method for H₂O₂ synthesis, but its application is limited by insufficient catalyst selectivity, active site depletion, and low productivity. By regulating the crystal structure, high-dimensional rod-like molybdenum oxide (HDS-MoO_x) was successfully synthesized, which is a non-traditional phase distinct from the thermodynamically stable α-MoO₃. This unique high-dimensional architecture not only exposes abundant meta-stable Mo⁵⁺ active sites but also enables reversible Mo⁵⁺/Mo⁶⁺ valence cycling to stabilize active-site regeneration. Compared with the conventional α-MoO₃, HDS-MoO_x showed a significant improvement in ORR performance, with a H₂O₂ Faraday efficiency of 97% and a high average yield of 875 mmol g_cat ^-1 h^-1, which is more than twice that of transition metal catalysts reported in the literature. Mechanistic studies reveal that the high-dimensional structure promotes oxygen vacancy formation, exposing Mo⁵⁺ active sites for O₂ activation. Meanwhile, the reversible Mo⁵⁺/Mo⁶⁺ valence cycling effectively mitigates site depletion, ensuring long-term catalytic stability. This work proposed a novel strategy for the efficient electroproduction of H₂O₂, offering valuable insights into the design of high-performance 2e^- ORR catalysts.