Sustainable and scalable in-situ fabrication of Au nanoparticles and Fe3O4 hybrids as highly efficient electrocatalysts for the enzyme-free sensing of H2O2 in neutral and basic solutions

The easy, green, and energy-saving fabrication of high-performance electrocatalysts toward detecting trace amounts of hydrogen peroxide (H2O2) in different media remains challenging for a sustainable future. Herein, we establish a one-pot fabrication of Au nanoparticles and Fe3O4 hybrids (Au/Fe3O4) through a sustainable and scalable protocol involving the redox reduction between chloroauric acid and ferrous sulfate at room temperature. The method does not require any additional reducing agent, organic solvent or energy input. Despite the protocol's simplicity, the achieved magnetic Au/Fe3O4 exhibits excellent H2O2 detection properties, i.e., a low detection limit of 0.108 mu M (S/N = 3), a wide linear detection range of 0.001-1 mM, a high sensitivity of 266 mu A mM(-1) cm(-2), and high selectivity in PBS solution. This electrocatalyst can be used to detect H2O2 in milk and juice samples below the residue limit required by the US Food and Drug Administration (< 14.7 mu M). The Au/Fe3O4 hybrid can also be used to detect H2O2 in basic solution with improved electrocatalytic performance. This simple method can further be extended to prepare other metals (Pd, Pt, and Ag)/Fe3O4 for electrocatalytic enzyme-free H2O2 sensing with high efficiency.