Hierarchical hollow metal nanostructure arrays for selective CO₂ conversion

Metal hollow nanostructures have a wide range of potential applications in energy storage and conversion, owing to their low density, high surface to volume ratio, and high contact surface area. However, the fabrication of such nanostructures remains challenging to date, with most fabrication routes only limited to specific materials. Herein, a universal templating strategy for fabricating hierarchical and aligned arrays of hollow metal nanostructures, from a variety of metallic materials including Cu, Ag, Ni and Pd, is reported. By using copper as a representative material, it is demonstrated that these nanostructures exhibit an enhanced electrocatalytic activity for CO₂ conversion, with the Cu nanostructures producing more than 205% and 183% higher yield for CO and H2 respectively, compared to non-nanostructured plain copper films at an applied potential of -2.4 V vs. Ag/AgCl. This work opens up a new route for fabricating hollow nanostructures with tailored metal compositions for energy storage and conversion applications.