Reduced graphene oxide supported nickel tungstate nano-composite electrocatalyst for anodic urea oxidation reaction in direct urea fuel cell

Abstract

In recent time direct urea fuel cell (DUFC) emerges as a potential candidate for sustainable urea reach wastewater treatment and power generation. The efficiency of DUFC mainly governed by the anodic urea oxidation reaction (UOR) kinetics. The design and development of efficient electrocatlysts for UOR remains a key factor for practical utilization of DUFC. In current study, we present a single step hydrothermal synthesis of NiWO4 NPs/rGO (h-NiWO4 NPs/rGO) composite for UOR catalysis in alkaline medium. The synthesized NiWO4 NPs/rGO composite offers a 218 mA/cm2 UOR catalytic current density. Moreover, the h-NiWO4 NPs/rGO composite retains its 94% UOR catalytic current after 1000 cyclic voltammetric cycles. Further, h-NiWO4 NPs/rGO composite shows superior UOR catalytic performance than physical mixture of NiWO4 NPs and rGO, NiWO4 NPs, NiO/WO3 physical mixture and only NiO with reference to catalytic current density, onset potential, and durability. The enhanced electrocatalytic activity of the h-NiWO4 NPs/rGO composite attributed to the synergetic coupling of physiochemical properties of NiWO4 NPs and rGO which improves the charge transfer generates larger electroactive surface and reduces catalyst poisoning. An air cathode DUFC with h-NiWO4 NPs/rGO composite modified anode and Pt/C cathode produces a maximum power density of 5.1 mW/cm2 and 927 mV open circuit potential.