The Role of Carbon Functionalities in the Incorporation of Pseudocapacitive Inorganic Phases for Improved Capacitance

Supercapacitors based on carbon materials have shown high power densities compared to rechargeable batteries, but lower energy densities. The introduction of pseudocapacitive materials, such as conducting polymers and/or different inorganic phases, in different carbons have open the possibility to improve the intrinsic capacitance of the electrode materials,  and by consequence the energy densities of the assembled devices. One of the main drawbacks of most inorganic materials is their low electric conductivity, which is somehow compensated when they are incorporated into a carbon matrix. Another strategy has been the introduction of certain functional groups in carbon to promote an intimate interaction with the inorganic compounds, resulting in improved electrochemical properties of the electrode materials for supercapacitors. In these sense, different carbon materials have been modified with different functional groups (-OH, -COOH, -CHO, NH2) to evaluate their effect with different inorganic phases, such as polyoxometalate (POM) or vanadyl phosphate (VOPO₄). The resulting nanocomposite materials (C-POM, C-VOPO4) have been characterized by XRD, FTIR, N₂ and CO₂ isotherms, and most importantly in acidic or neutral aqueous electrolyte where their improved capacitance values have been calculated.