Acid-Etched CoO Nanoparticles on Nickel Foam: The Highly Reactive (311) Facet and Enriched Defects for Boosting Methanol Oxidation Electrocatalysis.

The confirmation and regulation of active sites are particularly critical for the design of methanol oxidation reaction (MOR) catalysts. Here, an acid etching method for facet control combined with defect construction was utilized to synthesize CoO nanoparticles on nickel foam for preferentially exposing the (311) facet with enriched oxygen vacancies (V). The acid-leached oxides exhibited superior MOR activity with a mass activity of 710.94 mA mg and an area-specific activity of 3.390 mA cm as a result of (i) abundant active sites for MOR promoted by V along with the highly active (311) facet being exposed and (ii) phase purification-reduced adsorption energy () of methanol molecules. Ex situ X-ray photoelectron spectroscopy proved that highly active CoOOH obtained via the activation of plentiful Co effectively improved the MOR. Density functional theory calculations confirmed that the selective exposed (311) facet has the lowest for CHOH molecules. This work puts forward acid etching as the facet modification and defect engineer for nanostructured non-noble catalysts, which is expected to result in superior electrochemical performance required for advanced alkaline direct methanol fuel cells.