Reduced graphene oxide supported palladium nano-shapes for electro-oxidation of oxalic acid

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 2019-08, Vol.847, p.113167, Article 113167
• Main Authors: Kesavan, Lokesh, Kalekar, Ajit M., Damlin, Pia, Kvarnström, Carita
• Format: Article
• Language: English
• Subjects: Acidic oxides; Ascorbic acid; Catalysis; Catalytic activity; Chemical reduction; Colloiding; Composite materials; Electro-catalysis; Electrochemical oxidation; Ethylene glycol; Glassy carbon; Glassy carbon electrode; Graphene; Hybrid composite; Hybrid composites; Icosahedrons; Mathematical morphology; Morphology; Nanoparticles; Nanostructure; Organic chemistry; Oxalic acid; Palladium; Palladium nanocubes; Palladium nanoicosahedrons; Particle size distribution; Polyvinylpyrrolidone; Potassium bromides; Reduced graphene oxide; Reducing agents; Stabilizers (agents)
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2019.05.049

Size & shape controlled synthesis of metal nanoparticles are of high importance in catalysis. Colloidal techniques offer fine tunings in synthesis process as it involve multiple steps and reaction parameters. An efficient way of producing morphology controlled palladium nanostructures viz. palladium nanocubes (Pd-nc), palladium nanoicosahedrons (Pd-nico) supported on reduced graphene oxide (rGO) and its application in electro-catalysis is reported here. These Pd nano-shapes were achieved via sequential chemical reduction of Pd metal precursor and graphene oxide in the presence of reductant, ethylene glycol (EG) and stabilizer (capping agent), polyvinylpyrrolidone (PVP). Potassium bromide (KBr) and ascorbic acid (AA) were used as structure directing and secondary reducing agents respectively, to tune the geometry of Pd nanoparticles (Pd NPs). The preparation steps were optimized to yield cube shaped Pd nanoparticles (Pd-nc) with mean diameter of 4nm in the presence of KBr/AA; while in their absence, icosahedron shaped Pd nanoparticles (Pd-nico) with mean diameter of 3.1nm were formed and then homogeneously distributed over rGO sheets as evidenced by SEM-EDX and TEM. Further, Pd-nc/rGO and Pd-nico/rGO hybrid composite materials were used to investigate the electrochemical oxidation of oxalic acid (OA) in acidic medium. The results reveal that, these optimal size ranged nanostructures exhibit enhanced electro-catalytic activity when compared to bare glassy carbon electrode (GCE), towards OA oxidation. Among the two, Pd-nico/rGO showed enhanced activity than Pd-nc/rGO. The activity difference was justified based on the particle size distribution and no of surface exposed sites. The synthesis approach provides a versatile route for morphology (shape and size) controlled synthesis of metal nanostructures immobilized on support materials aiming towards fabrication of low cost composites in electro-catalysis and potential sensor applications. Shape selective synthesis of Pd nanoparticles & their catalytic performance in OA electro-oxidation. [Display omitted] •rGO supported Pd nanocubes (Pd-nc) and Pd nanoicosahedrons (Pd-nico) were prepared by one pot sequential reduction method•KBr/AA couple facilitates shape selective synthesis of Pd-nc, whereas high temperature promotes the formation of Pd-nico•Electro-oxidation of oxalic acid (OA) was performed using Pd-(nc, nico)/rGO modified glassy carbon electrodes in 0.1 M H2SO4•3 nm mean sized Pd-nico on rGO was more act