Lattice Oxygen Engineering in Ni-Co Hydroxides for Efficient Methanol Oxidation Coupled With Hydrogen Production

Electrocatalytic methanol oxidation reaction (MOR) coupled with hydrogen evolution (HER) can lower the energy cost of H₂ production while valorizing methanol to formate. Developing efficient, low-cost MOR catalysts for alkaline media remains challenging. Here, we report nickel-cobalt bimetal hydroxide (NiCoO_xH_y) nanosheets as a highly active and durable MOR catalysts. The optimized NiCoO_xH_y requires only 1.40 V versus the reversible hydrogen electrode (RHE) to deliver a current density of 400 mA cm^-2 and achieves >99% Faradaic efficiency toward formate at 1.45 V, representing one of the most efficient MOR electrocatalysts reported. In a two-electrode system, methanol oxidation coupled with HER lowers the cell voltage by ∼310 mV compared to conventional water electrolysis at 300 mA cm^-2. In situ Raman and x-ray absorption spectroscopy, together with isotope-labeling studies, reveal that cobalt incorporation promotes the formation of high-valence M⁴⁺ species, which activate lattice oxygen and accelerate methanol electrooxidation. Density functional theory (DFT) calculations confirm that highly oxidized M⁴⁺ species enhance metal-oxygen orbital hybridization, activating lattice oxygen and reducing reaction barriers. This work highlights lattice oxygen engineering via electronic structure modulation as an effective strategy for designing advanced electrocatalysts toward sustainable hydrogen-formate co-production.