Operando *OH Tracking Unveils Heteroatom-TailoredCo3O4 Spinel Catalyst for Industrial-Level CurrentDensity Ethylene Glycol Electrooxidation

Nucleophile electrooxidation-assisted hydrogen production embodies an efficient strategy that produces energy-efficient hydrogen energy and value-added products. However, conventional anodic catalysts, with single reactive sites, often face challenges like sluggish oxidation kinetics, electrode corrosion, etc. A Ni_1.2Cu_0.6Co_1.2O₄ catalyst with multiple reactive sites was synthesized via Ni, Cu heteroatom modulation of spinel Co₃O₄. An applied potential of 1.34 V versus reversible hydrogen electrode was applied to achieve 100 mA cm^–2 for the ethylene glycol electrooxidation reaction (EGOR), which was reduced by 250 mV compared to that required for the oxygen evolution reaction, with formate identified as the primary EGOR product. Additionally, the Ni_1.2Cu_0.6Co_1.2O₄/Ni foam catalyst was applied as an anode in a membrane electrode assembly flow electrolyzer, demonstrating operational stability exceeding 170 h at 300 mA cm^–2. The substitution of Co³⁺(Oh) and Co²⁺(Td) with Ni³⁺ and Cu²⁺, respectively, facilitated synergistically enhanced specific adsorption of nucleophiles and hydroxyl radicals (*OH) as well as nucleophile oxidation reaction kinetics. Using ethylene glycol as a model molecule, operando nuclear magnetic resonance and Fourier transform infrared spectroscopy realized operando *OH tracking and EGOR intermediate determination, revealing the *OH transfer pathway in both EG dehydrogenation and product synthesis processes, providing in-depth insight into the reaction mechanism of EGOR.