Unusual Effect of Trace Water on the Structure and Activity of Nix Co1-x Electrocatalysts for the Methanol Oxidation Reaction

Acid-Etched Co3O4 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 Co₃O₄ nanoparticles on nickel foam for preferentially exposing the (311) facet with enriched oxygen vacancies (V_O). The acid-leached oxides exhibited superior MOR activity with a mass activity of 710.94 mA mg^-1 and an area-specific activity of 3.390 mA cm^-2 as a result of (i) abundant active sites for MOR promoted by V_O along with the highly active (311) facet being exposed and (ii) phase purification-reduced adsorption energy (E_ads) of methanol molecules. Ex situ X-ray photoelectron spectroscopy proved that highly active CoOOH obtained via the activation of plentiful Co²⁺ effectively improved the MOR. Density functional theory calculations confirmed that the selective exposed (311) facet has the lowest E_ads for CH₃OH 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.

Recent Advances in Bio-Templated Metallic Nanomaterial Synthesis and Electrocatalytic Applications

Developing metallic nanocatalysts with high reaction activity, selectivity and practical durability is a promising and active subfield in electrocatalysis. In the classical "bottom-up" approach to synthesize stable nanomaterials by chemical reduction, stabilizing additives such as polymers or organic surfactants must be present to cap the nanoparticle to prevent material bulk aggregation. In recent years, biological systems have emerged as green alternatives to support the uncoated inorganic components. One key advantage of biological templates is their inherent ability to produce nanostructures with controllable composition, facet, size and morphology under ecologically friendly synthetic conditions, which are difficult to achieve with traditional inorganic synthesis. In addition, through genetic engineering or bioconjugation, bio-templates can provide numerous possibilities for surface functionalization to incorporate specific binding sites for the target metals. Therefore, in bio-templated systems, the electrocatalytic performance of the formed nanocatalyst can be tuned by precisely controlling the material surface chemistry. With controlled improvements in size, morphology, facet exposure, surface area and electron conductivity, bio-inspired nanomaterials often exhibit enhanced catalytic activity towards electrode reactions. In this Review, recent research developments are presented in bio-approaches for metallic nanomaterial synthesis and their applications in electrocatalysis for sustainable energy storage and conversion systems.