Facile synthesis of three-dimensional platinum nanoflowers on reduced graphene oxide - Tin oxide composite: An ultra-high performance catalyst for methanol electro-oxidation

Herein, we report platinum (Pt) nanoflowers decorated reduced graphene oxide (rGO)-tin oxide (SnO2) composite as an efficient electro-catalyst for direct methanol fuel cells (DMFCs). rGO-SnO2 composite is synthesized by a novel, eco-friendly hydrothermal method using lemon extract followed by electro-deposition of Pt to yield high density Pt nanoflowers uniformly distributed over rGO-SnO2 for superior catalytic performance and optimal utilization of Pt nanostructures. Whilst Pt nanoparticles (NPs)-rGO-SnO2 composite exhibits higher CO tolerance ability (If/Ib = 3) and poor catalytic stability, Pt nanoflowers-rGO-SnO2 composite shows comparable CO tolerance ability (If/Ib = 1.81) with excellent stability. At 3000 s, the current density of Pt nanoflowers-rGO-SnO2 has been found to be 2.1 folds higher than Pt NPs-rGO-SnO2 composite. Excellent durability of Pt nanoflowers-rGO-SnO2 is attributed to the high surface area of Pt nanoflowers which provides more active sites during methanol oxidation without any agglomeration, thus, facilitating diffusion of methanol to Pt for catalytic activity. As per our knowledge, this is the first report on Pt nanoflowers-rGO-SnO2 composite based electro-catalyst for DMFCs that yields superior performances in terms of catalytic efficiency, CO tolerance activity and stability. The composite shows enormous potential to be used as binder free, cost-effective, efficient and durable electro-catalyst for DMFCs applications.