In situ electro-organic synthesis of hydroquinone using anisole on MWCNT/Nafion modified electrode surface and its heterogeneous electrocatalytic reduction of toxic Cr(vi) species.

Owing to its electro-inactive character, anisole (phenylmethyl ether, PhOCH 3 ) and its related derivatives have been used as electrolytes in electrochemistry. Herein, we report a simple one-step electro-organic conversion of PhOCH 3 to hydroquinone (HQ) on a pristine-MWCNT-Nafion modified electrode glassy carbon electrode surface, GCE/Nf-MWCNT@HQ, in pH 2 KCl-HCl solution within 15 min of working time. The chemically modified electrode showed a highly redox-active and well-defined signal at an apparent standard electrode potential, E o ' = 0.45 V vs. Ag/AgCl (A2/C2) with a surface excess value, Γ HQ = 2.1 × 10 -9 mol cm -2 . The formation of surface-confined HQ is confirmed by collective physicochemical and spectroscopic characterizations using TEM, UV-Vis, Raman, FTIR, NMR and GC-MS techniques and with several control experiments. Consent about the mechanism, the 2.1% of intrinsic iron present in the pristine-MWCNT is involved for specific complexation with oxygen donor organic molecule (PhOCH 3 ) and hydroxylation in presence of H 2 O 2 (nucleophilic attack) for HQ-product formation. The GCE/Nf-MWCNT@HQ showed an excellent heterogeneous-electrocatalytic reduction of Cr(vi) species in acidic solution with a linear calibration plot in a range, 5-500 ppm at an applied potential, 0.4 V vs. Ag/AgCl with a detection limit, 230 ppb (S/N = 3; amperometric i - t ). As a proof of concept, selective detection of toxic Cr(vi) content in the tannery-waste water has been demonstrated with a recovery value ∼100%.