Ni(OH)2/graphene nanoplatelet composite as an electrocatalyst for urea oxidation.

• Synthesis of Ni(OH) 2 /graphene nanoplatelets composite under reflux condition. • Ni dispersion on graphene nanoplatelet has been confirmed with TEM analysis. • Ni dispersed over composite facilitates stability and exposure of active sites. • Tafel slope analysis suggests preferential oxidation of urea over OER. In this work, Ni(OH) 2 decorated over graphene nanoplatelets (GNP) synthesised by simple reflux reaction using hydrazine as complexing agent and sodium borohydride as reducing agent. Nickel-graphene platelet (NGP) composites are labelled as NGP-I,II and III for varying Ni-to-GNP ratios. Ni(OH) 2 anchoring on GNP has been confirmed with TEM and EDS analysis. The in situ growth of Ni(OH) 2 on graphene increases the stability and active sites of electrocatalysts for water splitting and direct oxidation of urea. The OER and urea oxidation on NGP-III composite were studied in 1 M KOH electrolyte, exhibiting lower potential of 1.53 V and 1.34 V vs. RHE and Tafel slope of 47 mV dec–1 and 56 mV dec–1, respectively. The negative shift in the oxidation potential of urea suggest that the urea oxidation is preferred over OER. [ABSTRACT FROM AUTHOR]