Compósitos de grafeno amassados decorados por nanopartículas de metais de transição: viabilidade de aplicação como sensores eletroquímicos

Abstract

Graphene-based materials have great potential for a myriad of applications such as energy storage devices, flexible electrodes for photovoltaic cells, sensors, and nanocomposites, among others. The structure of graphene directly influences the performance of the material and the production of 3D graphene-based materials is an alternative to retain the intrinsic properties of 2D graphene and improve other properties such as specific surface area, porosity, mechanical properties, etc. In this sense, nanocomposites based on 3D graphene (crumpled graphene, CG) were synthesized, maintaining the high active area and minimizing the material's aggregation behavior. The synthesis of composites is an alternative to achieve a synergistic effect, where graphene acts as a substrate to immobilize other components such as inorganic nanoparticles, improving the electrochemical properties of the carbon nanostructure. The aerosol-assisted capillary compression strategy adopted to synthesize the composites results in transition metal nanoparticles directly connected to the CG. The carbon nanostructure controls the nucleation and growth of nanoparticles during capillary compression, making carbonaceous structures one of the main research focuses to develop materials for various technological applications, such as electrochemical sensors. In this context, the goal of this work was to synthesize and characterize crumpled graphene nanostructures decorated with nanoparticles of transition metals, such as copper, palladium, and nickel, exploring its promising application as an efficient electrocatalyst in the electrochemical detection of hydrogen peroxide, glycerol, caffeine. The synthesis of CG with the different metallic precursors was carried out in a single step using a horizontal tube furnace, in a spray pyrolysis process. The materials obtained were characterized by scanning electron microscopy, transmission electron microscopy and X-ray excited photoelectron spectroscopy, energy dispersive spectroscopy, X-ray diffraction and thermogravimetric analysis in which the morphology attributed to the crumpled graphene and the presence of metal nanoparticles covering the surface of the carbonaceous material were verified. In addition, electrochemical measurements were performed to investigate the electrocatalytic properties of the sensors by the techniques of cyclic voltammetry and chronoamperometry. The 1:5 CG:Cu nanocomposite showed good sensitivity and linearity in the response curves for H2O2, with detection limit and sensitivity of 0.64 µmol L-1 and 0.37 A L mol-1 cm-2 , respectively. The Pd/CG composite showed sensitivity for the detection of H2O2, caffeine and glycerol of 0.742, 0.848 and 8.24x10-4 A L mol-1 cm-2 , respectively. And the CG:Ni-Acet and CG:Ni-Nit nanocomposites showed excellent electrocatalytic activity in the oxidation of H2O2 with the sensitivity of 0.357 and 0.317 A L mol-1 cm-2 , respectively. In addition, the synthesized composites are reproducible, selective, stable and have a rapid electrochemical response.