Elucidating the role of etchants induced photo- and electro-activity in holey graphene oxide and graphene quantum dots composites for textile electrode applications

Abstract

Holey graphene oxide (HGO) can unlock the potential of graphene oxide (GO) by providing high surface area, increased surface reactivity, and fast electrolyte flow. Generally, HGOs are prepared by etching GO, and graphene quantum dots (GQDs) are formed as a byproduct during the etching. GQDs are active materials to increase charge mobility and reduce charge recombination. Previous studies employed strong and high boiling point etchants (e.g., H2SO4), and a filtration process is required for purification. GQDs remained in the filtrate and were lost during the purification because of their small size. To avoid the wastage of GQDs, we tested the low boiling point etchants, which can be separated via vacuum drying to retain GQDs. Considering easy recovery, H2O2, NH4OH, and HNO3 were used for etching, and the resulting composite of GQDs and HGO was characterized and tested for photocatalytic and electrocatalytic activity. The active composite materials were loaded on carbon cloth and reduced to fabricate a stable electrode for performance evaluation. Amongst all etchants, NH4OH could generate the highest surface roughness and nitrogen doping. The NH4OH etched HGO & GQDs composite demonstrated excellent photocatalytic and electrocatalytic activity due to its enhanced surface reactivity, despite its reduced surface area. Compared to negligible photocatalysis of rGO, the optimized composite of GQDs and HGO showed nearly complete dye degradation in 4 h.