A High-Capacity Semiconductor Organic Polymer for Stable Aqueous Ammonium-Ion Storage

In aqueous ammonium-ion storage (AAIS), effective hydrogen-binding sites are crucial for designing high-performance ammonium ions (NH₄ ⁺) host materials. The organic small molecule tetraamino-p-benzoquinone (TABQ) shows great potential in AAIS due to its unique hydrogen-bonding interactions with NH₄ ⁺. However, such small-molecule materials typically exhibit severe dissolution in aqueous electrolytes. Moreover, their low conductivity severely hampers their ability to store ammonium ions. To address these challenges concurrently, a chain amide polymer (PPAT) is designed by introducing a 3,4,9,10-perylenetetracarboxylic dianhydride to extend the skeleton of TABQ. This polymer exhibits an ultralow solubility of 0.00058 mg mL^-1 and introduces substantial functional groups for hydrogen-bonding interactions. The conjugated effect is further extended by combining it with polyaniline (PANI). The spectral and computational results indicate that the designed material possesses an elevated HOMO energy level, a reduced LUMO energy level, and a smaller bandgap. The delocalization of electrons throughout the entire molecule leads to a semiconducting nature. The organic polymer electrode delivers a high capacity of 291.81 mAh g^-1 at 1 A g^-1, outperforming state-of-the-art NH₄ ⁺ storage organic materials. The energy storage mechanism of the hydrogen-bonding interactions between the organic polymer and NH₄ ⁺ is investigated, and the active sites that contribute to high capacity are identified.