NiMoO4@NiMnCo2O4 Heterostructure: A Poly(3,4-propylenedioxythiophene) Composite-Based Supercapacitor Powers an Electrochromic Device.

The hierarchical heterostructure of NiMoO4@NiMnCo2O4 (NMO@NMCO) with furry structures of NMCO juxtaposed with NMO nanowires are endowed with multiple electrochemically active and accessible sites for ion storage, thus delivering an ultrahigh specific capacitance of 2706 F g-1, nearly two-fold times greater than that of sole NMCO. Electrodeposition of an overlayer of a highly robust and electrically conducting polymer, poly(3,4-propylenedioxythiophene) (PProDOT), not only improves the energy storage performance but also assists the binary oxide cathode in retaining its structural integrity during redox cycling. Coupling with an anode of porous flaky carbon (FC) derived from groundnut shells results in an asymmetric supercapacitor of FC//PProDOT@NiMoO4@NiMnCo2O4, which delivers an outstanding capacitance of 552 F g-1, energy and power density ranges of 172-40 Wh kg-1 and 0.75-10 kW kg-1, respectively, and a remarkable cycle life of 50 000 cycles, with ∼97.8% capacitance retention, over an operational voltage window of 1.5 V. From an application perspective, the charged supercapacitor was connected to a complementary coloring reversible electrochromic device (ECD) of Prussian blue//PProDOT, and the ECD state transformed from a pale-blue to a deep blue hue, thus signaling the efficient utilization of energy stored in the supercapacitor. The energy-saving attribute of the ECD was realized in terms of an integrated visible-light modulation of 39% that accompanied the optical transition. Deployment of low-cost devices at homes and commercial spaces, capable of storing and saving energy, is the way forward, and this is one significant step in this direction.