Confined interfacial self-assembly of graphene-like carbon/MXene composite electrodes for capacitive deionization

Abstract

Electrodes that have high desalting capacity, fast desalting rates and stable desalination performance are needed in capacitive deionization (CDI) technologies for water security. Herein, confined interfacial self-assembly of lignin-based graphene-like carbon (GC) precursors in Ti3C2-MXene interlayers was developed for forming GC/MXene composites. The formation of GC was generated in-situ by KHCO3-assisted pyrolytic carbonization which leads to exfoliation of multilayered MXene thereby forming GC/MXene heterostructures having strong interfacial interactions. GC/MXene exhibited tremella-like nanosheets morphology, accompanied by the formation of a TiO2 phase at the interface of GC and MXene hybridization, which confirmed formation of a heterostructure. Crystallographic phase identification of GC/MXene showed the exfoliation of MXene. GC/MXene had an ultra-negative surface charge of −39.3 mV, making it favorable for application as a cathode for Na+ removal. The GC/MXene heterostructure had high desalting capacity (54.2 mg g−1), high desalting rate (2.7 mg g−1 min−1), and stable cycling performance (90 % SAC retention after 30 cycles). The interfacial self-assembly strategy developed in this work is expected to enable green synthesis routes for graphene/MXene-based composite materials that allow construction of 2D/2D heterostructures for multilayer MXene and their analogues.