Sulfur substitution for lattice oxygen in Co(OH)2 activates the lattice oxygen-mediated mechanism for enhancing oxygen evolution reaction

Water electrolysis for hydrogen production is a highly promising sustainable technology, yet its advancement is hindered by the sluggish kinetics of the anodic oxygen evolution reaction (OER). The lattice oxygen-mediated mechanism (LOM) can offer electrocatalysts faster kinetics than the adsorbate evolution mechanism (AEM). Developing effective strategies to activate the Lattice Oxygen-Mediated mechanism (LOM) is one of the major challenges in the field of hydrogen production through water electrolysis. Herein, we report a sulfur ion-mediated strategy for the in-situ derivation of sulfur-doped cobalt oxyhydroxide (S−CoOOH) from Co(OH) 2 via lattice oxygen substitution, which effectively activates the LOM, allowing for the controllable preparation of a highly active OER catalyst. Furthermore, an integrated OER electrode was constructed by coupling S−CoOOH with nickel foam (S−CoOOH/NF), which provides a current density of 10 mA cm −2 at an overpotential of only 279 mV in alkaline medium, far lower than the 320 mV required for its corresponding Co(OH) 2 /NF electrode. The successful sulfur-for-oxygen substitution in Co(OH) 2 is directly confirmed by Raman, X-ray absorption fine structure (XAFS), and X-ray photoelectron spectroscopy (XPS). Subsequent pH-dependent activity, along with in situ Raman and 18 O-labeled differential electrochemical mass spectrometry (DEMS) measurements, collectively confirms that this structural modification effectively activates the LOM. Density functional theory (DFT) analyses reveal that sulfur substitution shifts the O 2p band closer to the Fermi level ( E F ), which favors lattice oxygen release, thereby activating the LOM. These findings contribute to a deeper understanding of the LOM activation pathways and accelerated reaction kinetics, thereby guiding the rational design of highly active OER catalysts based on non-noble materials. Sulfur substitution for lattice oxygen in Co(OH) 2 , enabled by S doping and morphology control, effectively drives the lattice oxygen mechanism (LOM), leading to a significant enhancement of electrocatalytic activity. This work provides new insights into the activation of the LOM in non-noble materials, thereby guiding the design of highly active OER catalysts based on non-noble materials.