Suppressing lattice expansion via engineering oxygen vacancy into sub-5nm NiO for durable methanol electrooxidation

Replacing the sluggish oxygen evolution reaction (OER) with the electrocatalytic methanol oxidation reaction (MOR) is a promising energy-saving hydrogen production strategy with high-value chemical co-production. However, the electrocatalytic reconstruction at high reaction potentials is prone to catalyst structure collapse due to over-oxidation and lattice expansion, resulting in the loss of active sites and decreased stability. Herein, we presented an oxygen vacancy-rich sub-5 nm electrocatalyst (Nano-Vo-NiO) through a sol-gel-assisted hydrothermal-calcination process integrated with low-temperature plasma modification. The champion catalyst Nano-Vo-NiO operated more than 1000 hours at an industrial-level current density of ~ 500 mA cm ^− 2 , with a Faradaic efficiency of formate above 94.1% in a membrane electrode assembly (MEA). Operando X-ray absorption spectroscopy (XAS) demonstrated that the vacancy structure remains stable throughout the electrocatalytic process, inhibiting the elongation of Ni-Ni bonds and restricting lattice expansion during the electrocatalytic process. Density functional theory (DFT) calculations revealed that the vacancy structure reduces the proton deintercalation energy barrier, thus achieving efficient MOR activity and stability. This study highlights oxygen vacancies as a critical factor in nanoelectrocatalysis and delivers novel design principles and pathway regulation strategies for efficient electrocatalytic organic oxidation.