Electro Catalytic Properties of α, β, γ, ϵ ‐ MnO2 and γ ‐ MnOOH Nanoparticles: Role of Polymorphs on Enzyme Free H2O2 Sensing

Polymorphs of Manganese di oxide (MnO₂) such as alpha (α), beta (β), gamma (γ), epsilon (ϵ), and MnOOH type materials were prepared via hydrothermal approach under different conditions. The samples were characterized by XRD, FESEM, FT‐IR, Raman and BET analysis. Cyclic voltammetry (CV) analysis confirm that α ‐ MnO₂ shows better electro‐catalytic ability. Amperometry sensing of hydrogen peroxide (H₂O₂) was carried out by varying applied potential value with the polymorphs of MnO₂. Compared with the other phases of MnO₂, α ‐ MnO₂ shows high linear range up to 20μM. The calculated sensitivity value for H₂O₂ sensing of different phases is in the order of α ‐ MnO₂, β ‐ MnO₂, ϵ ‐ MnO₂, γ ‐ MnO_2, MnOOH and found to be 0.094 mA μM⁻¹ cm⁻² > 0.072 mA μM⁻¹ cm⁻² > 0.07 mA μM⁻¹ cm⁻² > 0.03 mA μM⁻¹ cm⁻² > 0.01 mA μM⁻¹ cm⁻² respectively. All the characterization results reveal that crystalline phase plays a vital role in electrochemical behavior rather than crystalline size, morphology, surface charge, surface area.