Scalable preparation of high-dispersion g-C3N4via GQDs-assisted ultrasonic exfoliation for accelerating cement hydration

Abstract

Tremendous progress has been made in the employment of two-dimensional (2D) nanomaterials in cement composites. However, high cost and poor dispersion of 2D nanomaterials immensely hinder their extensive use. To address these issues, in this work, a scalable, simple, and eco-friendly graphene quantum dots (GQDs)-assisted ultrasonic exfoliation approach was elaborately designed to efficiently delaminate and disperse bulk g-C3N4 (B–CN), thereby obtaining low-cost and high-dispersion CN (G-CN). And the effect of B–CN, B–CN exfoliated without GQDs (U–CN) and G-CN on cement hydration was comprehensively investigated for the first time. Specifically, G-CN possessed a remarkably higher dispersion and a larger specific surface area (32.92 m2 g−1) increasing by 44.45% and 183.55% than U–CN and B–CN, respectively. And based on characteristics of G-CN and properties of GQDs, the exfoliation mechanism of g-C3N4 was ascribed to intercalation, exfoliation, and surfactant effects of GQDs. More importantly, highly dispersed G-CN was more propitious to accelerate cement hydration and refine microstructure, thereby dramatically boosting the compressive strength of cement paste at 7-day curing by 10.1% and 25.0% compared with that of U–CN and B–CN, respectively. This work not only provided a scalable, facile and environmentally-friendly approach to efficiently fabricate well dispersive g-C3N4, but also firstly testified their evident accelerating effect on cement hydration. These findings would be conducive to advancing the application of 2D nanomaterials in cement composites.