Bifunctional 2D-on-2D MoO3 nanobelt/Ni(OH)2 nanosheets for supercapacitor-driven electrochromic energy storage

A hybrid composite that unifies multiple structural attributes is the key for improved functional device performance. Moreover, hierarchical and porous assembly of dissimilar constituent elements at various length scales and dimensionality is highly appropriate for mass transfer and surface/interfacial-dominated reactions. Here, we demonstrate solution processed 2D-on-2D hierarchical architecture of nanobelt core–nanosheets shell consisting of dissimilar transition metal composite. The defining benefits of such hetero-structured material design are short ion diffusion pathway of a thin 2D nanobelt core that is interfaced to large surface area and porous 2D nanosheets. Accordingly, an integrated energy system that delivers multiple functionalities, i.e. supercapacitive charge storage and electrochromic optical modulation, is investigated due to its attractive complementary energy storage and energy conservation capabilities. Consequently, bifunctional electrochromism–supercapacitive properties are demonstrated where desirable optical transmittance modulation and coloration efficiency properties in parallel with favorable pseudocapacitive storage and specific capacitance properties are simultaneously realized. Such an integrated energy system is anticipated to have a broad range of smart applications in buildings, automobiles and other emerging electronics needs.