Optimization of NiFeCrCoCu high entropy alloy nanoparticle – graphene (HEA-G) composite for the enhanced electrochemical sensitivity towards urea oxidation

Graphene as a single or few-layered 2D material acts as a stable and efficient substrate to build effective nanocomposite catalysts for numerous applications. In this study, a few layers of exfoliated graphene sheets are engineered with novel high entropy alloy (HEA) nanoparticles through mechanical milling technique followed by sonication. Three different HEA-Graphene (HEA-G) composites were produced with the metal-to-graphene weight ratio of 50:50, 70:30 and 90:10. As-synthesized HEA-G composites were extensively characterized through microscopy (AFM and TEM) and spectroscopic (Raman) techniques to understand the HEA nanoparticle formation and distribution over the surface of graphene sheets. Further, the catalytic behaviour of HEA-G composites was examined using cyclic voltammetry (CV) and chronoamperometry (CA) to understand the non-enzymatic oxidation of urea using the HEA-G composites. The onset of the catalytic behaviour was observed with the composite 50:50 which was increased till 70:30 composite. However, the 90:10 composition exhibited minimal catalytic response compared to the other two composites. The composite 70:30 being the best performer was used to derive sensitivity based on the oxidation of urea which was found to be 37.4 μAm M−1 cm−2. The current study opens the window to explore a new class of all possible HEA nanocomposites for electrocatalytic applications.