Facile one-pot synthesis and application of nitrogen and sulfur-doped activated graphene in simultaneous electrochemical determination of hydroquinone and catechol

Nitrogen (N) and sulfur (S) co-doped activated graphene (N, S-AGR) was prepared by the one-pot pyrolysis of a mixture of graphene oxide (GO), thiourea, and potassium hydroxide (KOH), where thiourea acts as the source of N and S dopants and KOH is the activator for porosity. N, S-AGR with a dopant abundance of 2.8 at% N and 2.3 at% S was then used as a high-activity electrocatalyst in the fabrication of an electrochemical sensor for simultaneous determination of dihydroxybenzene isomers, hydroquinone (HQ) and catechol (CC), in aqueous solution. Compared with the bare glassy carbon electrode (GCE), the electrodes modified with N, S-AGR showed enhanced electrochemical performance toward HQ and CC in both cyclic voltammetric (CV) and differential pulse voltammetric (DPV) measurements because of their enlarged surface area, enhanced electron-transfer rate and increased active sites. Compared with some recently reported electrochemical sensors based on graphene composites, the N, S-AGR modified electrode exhibits higher sensitivity, a much lower detection limit and a comparable linear range for the simultaneous determination of HQ and CC. Moreover, the proposed sensor is promising in practical application for the satisfactory recoveries obtained in real water sample analyses.