Phosphomolybdate@poly(diallyldimethylammonium chloride)-reduced graphene oxide modified electrode for highly efficient electrocatalytic reduction of bromate

• One-step fabrication of graphene–polyelectrolyte composite modified electrodes.
• Enhanced phosphomolybdate loading and phosphomolybdate/electrode communication.
• Electrocatalytic reduction of bromate with high stability and efficiency.
• Detailed mechanistic study using rotating disk electrode method.

Phosphomolybdate ([PMo12O40]3− or PMo12) was adsorbed onto a poly(diallyldimethylammonium chloride) functionalized reduced graphene oxide (rGO-PDDA) modified glassy carbon electrode (GCE). Compared to monolayer formation of PMo12 on a bare GCE, the rGO-PDDA electrode has a significantly increased loading of PMo12, due to its much larger surface area. The presence of positively charged PDDA also favors the adsorption of negatively charged PMo12 and enhances the stability of the modified electrode. The fabricated electrode (PMo12@rGO-PDDA/GCE) was characterized by scanning electron microscopy as well as energy dispersive X-ray, Raman and FT-IR spectroscopies and applied to the electrocatalytic reduction of bromate. Cyclic voltammetry showed that PMo12@rGO-PDDA/GCE exhibits high electrocatalytic performance and good stability for the reduction of bromate. A wide linear current vs. bromate concentration response (0.02–10 mM) was achieved with excellent sensitivity (454 μA cm−2 mM−1). The kinetics for the electrocatalytic reduction of bromate and the number of electron involved were evaluated using the rotating disk electrode method.