Tailored super-microporous pitch-based carbon with small graphitic domains achieving high capacitive desalination performance

Abstract

Carbon materials combining ultra-micropores and long-range graphitic domains are highly desired for enhancing their capacitive deionization (CDI) properties, but conventional fabrication strategies struggle with this trade-off contradiction. Herein, a novel pitch molecular design strategy is developed, combining diphenylurea-induced thermal polycondensation with potassium hydrogen phthalate-assisted activation. As-obtained carbon (DMPC) exhibits ultra-microporosity (0.8 nm) and order-in-disordered pseudographitic domains. Benefiting from systematic engineering of tailored pore size modulation, the active sites of nitrogen configurations on the micropore lattice scaffolds are significantly enhanced, reducing charge transfer resistance and increasing ion transfer/storage capacity. The symmetric DMPC electrode has comprehensive CDI performance, showcasing a salt adsorption capacity of 42.4 mg g⁻¹ at an average desalination rate of 2.64 mg g⁻¹ min⁻¹ and a charging efficiency of 63.3 % at 1.4 V in a 500 mg L⁻¹ NaCl solution. Notably, the good cycling durability and antioxidant mechanism of DMPC are demonstrated in mixed salt solutions. This study sheds light on the potential of molecular design engineering of pitch to tailor porosity and graphitization, paving a new path in advanced carbon electrodes for capacitive deionization.