Visible-light driven catalase-like activity of blackberry-shaped {Mo72Fe30} nanovesicles: combined kinetic and mechanistic studies

Abstract

In this work, catalase-like activity of blackberry-shaped nanoparticles composed of giant {Mo₇₂Fe₃₀} clusters in aqueous solution under visible-light irradiation was exploited. The effects of the pH, buffer system, catalyst, H₂O₂ concentration, and optical conditions as well as morphology and crystallinity on the catalytic activity of the clusters were investigated. Our results under different conditions affirmed the superior catalytic activity of amorphous {Mo₇₂Fe₃₀} to that of its crystalline counterpart. The catalyst proved to be a visible-light-driven photocatalyst based on its narrow band gap (2.12 eV) and desired photoefficiency obtained at different wavelengths. The clusters preserved their integrity during treatment with hydrogen peroxide as evidenced by different spectral data as well as compositional analysis (EDS), providing efficient reusability under experimental conditions of this work. The reaction kinetic study demonstrated a first-order reaction with respect to H₂O₂ with a rate constant of 3 × 10⁻⁴ s⁻¹ at T = 298 K. The activation energy of the reaction was found to be 58.74 kJ mol⁻¹. A turnover frequency (TOF) of 0.03 s⁻¹ and turnover number up to ∼3800 were determined for the hydrogen peroxide decomposition process under visible light. Based on scavenging experiments, a non-radical mechanism for dismutation of hydrogen peroxide on the surface of the clusters was proposed.