Highly Active and Robust Cr-Doped Co3O4 Electrocatalyst for Acidic Oxygen Evolution via H-Receptor-Mediated Mechanism

Developing efficient and durable oxygen evolution reaction (OER) electrocatalysts for acidic media is vital for advancing proton exchange membrane water electrolyzers (PEMWEs) but remains highly challenging. In this work, a lattice-engineered Cr-doped Co 3 O 4 (Cr 0.3 -Co 2.7 O 4 ) electrocatalyst is constructed and achieves high activity and robustness for acidic OER. Spectroscopic and theoretical analyses reveal that Cr preferentially substitutes Co 3+ octahedral sites to form “CrO 6 ” units and transfers charge from Cr to the coordinated O atoms, activating them as intrinsic proton receptors. This unique functionality enables the formation of a bridged *O-O-H-O* intermediate, which circumvents the scaling relationship in the adsorbate evolution mechanism and accelerates OER kinetics. Meanwhile, Cr incorporation strengthens neighboring Co-O bonds, preserving structural integrity under acidic conditions. As a result, the Cr 0.3 -Co 2.7 O 4 electrocatalyst delivers an overpotential of 404 mV at 50 mA cm -2 , outperforming commercial IrO 2 (417 mV). In a PEMWE, it delivers 200 mA cm -2 at 1.71 V with 500 h continuous operation and only 18 μV h -1 degradation. This work establishes lattice engineering of intrinsic proton-accepting motifs as a viable strategy for designing efficient, durable and noble-metal-free electrocatalysts for acidic OER. The Cr-doped Co 3 O 4 (Cr 0.3 -Co 2.7 O 4 ) electrocatalyst is designed through the lattice-engineered strategy featuring precise control over the Cr substituting Co 3+ octahedral site to form “CrO 6 ” unit. Cr-to-O charge transfer enables the O atom to act as a proton acceptor that couples with *O-O-H to form a bridged *O-O-H-O* intermediate, promoting an effective oxygen evolution reaction via H-receptor-mediated adsorbate evolution mechanism. • Cr-doped Co 3 O 4 (Cr 0.3 -Co 2.7 O 4 ) catalyst is constructed by a lattice-engineered strategy. • Cr substituting Co 3+ octahedral site forms “CrO 6 ” unit with Cr-to-O charge transfer. • atoms function as proton acceptors to form a *O-O-H-O* intermediate that breaks the OER scaling relationship. • Efficient and robust proton-exchange-membrane water electrolyzer is realized with the Cr 0.3 -Co 2.7 O 4 catalyst.