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Capacitive deionization (CDI) is a desalination technology that shows promise for removing nitrate and phosphate ions. The main components of CDI cells are electrodes, which are typically made from activated carbon (AC). However, the electrosorption performance of AC electrodes is limited because of the negative zeta potential, hydrophobicity, and oxidation resulting in co–ions’ repulsion. This study investigates binder-free polypyrrole-coated nanocellulose (NC/PPy) electrodes, which are hydrophilic and possess various functional groups, as an alternative to AC electrodes. An asymmetric CDI cell with an NC/PPy positive electrode demonstrated greater energy and charge efficiencies compared to a symmetric cell. The NC/PPy electrode exhibited a threefold electrosorption capacity towards nitrate ions compared to the AC electrode, and 4.5 times higher than for phosphate ions. The electrosorption mechanism revealed by first-principles modeling indicates similar sorption energies for nitrate and phosphate ions, with higher nitrate capacity due to co-ion repulsion and diffusion effects.

The conversion of biomass and natural wastes into carbon-based materials for various applications such as catalysts and energy-related materials is a fascinating and sustainable approach emerged during recent years. Precursor nature and characteristics are complex, hence, their effect on the properties of resulting materials is still unclear. In this work, we have investigated the effect of different precursors and pyrolysis temperature on the properties of produced carbon materials and their potential application as negative electrode materials in Li-ion batteries. Three biomasses, lignocellulosic brewery spent grain from a local brewery, catechol-rich lignin and tannins, were selected for investigations. We show that such end-product carbon characteristic as functional and elemental composition, porosity, specific surface area, defectiveness level, and morphology strictly depend on the precursor composition, chemical structure, and pyrolysis temperature. The electrochemical characteristics of produced carbon materials are correlate with the characteristics of the produced materials. A higher pyrolysis temperature is shown to be favourable for production of carbon material for the Li-ion battery application in terms of both specific surface area and long-term cycling stability.