Promoting H₂O₂ production via 2-electron oxygen reduction by coordinating partially oxidized Pd with defect carbon

Electrochemical synthesis of H₂O₂ through a selective two-electron (2e⁻) oxygen reduction reaction (ORR) is an attractive alternative to the industrial anthraquinone oxidation method, as it allows decentralized H₂O₂ production. Herein, we report that the synergistic interaction between partially oxidized palladium (Pd^δ+) and oxygen-functionalized carbon can promote 2e⁻ ORR in acidic electrolytes. An electrocatalyst synthesized by solution deposition of amorphous Pd^δ+ clusters (Pd₃ ^δ+ and Pd₄ ^δ+) onto mildly oxidized carbon nanotubes (Pd^δ+-OCNT) shows nearly 100% selectivity toward H₂O₂ and a positive shift of ORR onset potential by ~320 mV compared with the OCNT substrate. A high mass activity (1.946 A mg⁻¹ at 0.45 V) of Pd^δ+-OCNT is achieved. Extended X-ray absorption fine structure characterization and density functional theory calculations suggest that the interaction between Pd clusters and the nearby oxygen-containing functional groups is key for the high selectivity and activity for 2e⁻ ORR.