Engineering Interface with One-Dimensional Co3O4 Nanostructure in Catalytic Membrane Electrode: Toward an Advanced Electrocatalyst for Alcohol Oxidation

Electrochemical oxidation has attracted vast interest as a promising alternative to traditional chemical processes in fine chemical synthesis owing to its fast and sustainable features. An electrocatalytic membrane reactor (ECMR) with a three-dimensional (3D) electrode has been successfully designed for the selective oxidation of alcohols with high current efficiency to the corresponding acids or ketones. The anode electrode was fabricated by the in situ loading of one-dimensional (1D) Co3O4 nanowires (NWs) on the conductive porous Ti membrane (Co3O4 NWs/Ti) via the combination of a facile hydrothermal synthesis and subsequent thermal treatment. The electrocatalytic oxidation (ECO) results of alcohols exhibited superior catalytic performance with a higher current efficiency on the Co3O4 NWs/Ti membrane compared with those of Co3O4 nanoparticles on the Ti membrane (Co3O4 NPs/Ti). Even under low reaction temperatures such as 0 °C, it still displayed a very high ECO activity for alcohol oxidation in the ECMR. For example, >99% conversion and 92% selectivity toward benzoic acid were obtained for the benzyl alcohol electrooxidation. The electrode is particularly effective for the cyclohexanol oxidation, and a selectivity of >99% to cyclohexanone was achieved at 0 °C, higher than most reported noble-metal catalysts under the aerobic reaction conditions. The extraordinary electrocatalytic performance of the 3D Co3O4 NWs/Ti membrane electrode demonstrates the significant influence of morphology effect and engineering interfaces in membrane electrodes on the electrocatalytic activity and charge transfer process of nanocatalysts. Our results propose that similar membrane electrodes serve as versatile platforms for the applications of 1D nanomaterials, porous electrodes, and ECMRs.