Covalently Interlayer-Confined Organic-Inorganic Heterostructures for Aqueous Potassium Ion Supercapacitors.

Artificial assembly of organic-inorganic heterostructures for electrochemical energy storage at the molecular level is promising, but remains a great challenge. Here, a covalently interlayer-confined organic (polyaniline [PANI])-inorganic (MoS 2 ) hybrid with a dual charge-storage mechanism is developed for boosting the reaction kinetics of supercapacitors. Systematic characterizations reveal that PANI induces a partial phase transition from the 2H to 1T phases of MoS 2 , expands the interlayer spacing of MoS 2 , and increases the hydrophilicity. More in-depth insights from the synchrotron radiation-based X-ray technique illustrate that the covalent grafting of PANI to MoS 2  induces the formation of MoN bonds and unsaturated Mo sites, leading to increased active sites. Theoretical analysis reveals that the covalent assembly facilitates cross-layer electron transfer and decreases the diffusion barrier of K + ions, which favors reaction kinetics. The resultant hybrid material exhibits high specific capacitance and good rate capability. This design provides an effective strategy to develop organic-inorganic heterostructures for superior K-ion storage. The K-ion storage mechanism concerning the reversible insertion/extraction upon charge/discharge is revealed through ex situ X-ray photoelectron spectroscopy.