Electrocatalytic oxidation and reduction of H2O2 on vertically aligned Co3O4 nanowalls electrode: Toward H2O2 detection

Single crystal and vertically aligned cobalt oxide (Co3O4) nanowalls were synthesized by directly heating Co foil on a hot-plate under ambient conditions. The vertically aligned Co3O4 nanowalls grown on the plate show excellent mechanical property and were facilely attached to the surface of a glassy carbon (GC) electrode using conductive silver paint. The prepared Co3O4 nanowalls electrode was then applied to study the electrocatalytic oxidation and reduction of hydrogen peroxide (H2O2) in 0.01 M pH 7.4 phosphate buffer medium. Upon the addition of H2O2, the Co3O4 nanowalls electrode exhibits significant oxidation and reduction of H2O2 starting around +0.25 V (vs. Ag/AgCl), while no obvious redox activity is observed at a bare GC electrode over most of the potential range. The superior electrocatalytic response to H2O2 is mainly attributed to the large surface area, minimized diffusion resistance, high surface energy, and enhanced electron transfer of the as-synthesized Co3O4 nanowalls. The same Co3O4 nanowalls electrode was also applied for the amperometric detection of H2O2 and showed a fast response and high sensitivity at applied potentials of +0.8 V and −0.2 V (vs. Ag/AgCl), respectively. The results also demonstrate that Co3O4 nanowalls have great potential in sensor and biosensor applications.