Controllable synthesis of ultrathin Co3O4 and construction of RuO2/Co3O4 interface for oxygen evolution performance

Abstract

Replacing noble metal catalysts with transition metal oxides is a key goal in catalysis research. However, obtaining well-defined ultrathin oxides remains challenging, unlike the relatively facile preparation of typical ultrathin crystals. Here, we report the vapor–liquid–solid (VLS) growth of ultrathin Co3O4 nanostructures, using CoCl2 as the precursor in combination with an oxygen-containing atmosphere. Single-crystalline, micrometer-scale, thickness-tunable epitaxial Co3O4 nanosheets were successfully synthesized on Al2O3(0001) substrates and displayed favorable oxygen evolution activity following the loading of RuO2. During the growth process, the cobalt-containing liquid intermediate and the dynamic liquid–solid interface play crucial roles in guiding the epitaxial alignment and promoting expansion of the oxide layer. This method enables the fabrication of structurally well-defined Co3O4 with tunable surface morphology and crystallographic orientation, and offers an ideal model system for investigating structure-dependent catalytic mechanisms and surface reactivity in transition metal oxide catalysts.