Generation of H2O2 by on-site activation of molecular dioxygen for environmental remediation applications: A review

The unique characteristics of H2O2 render it a versatile and green agent for environmental remediation applications. As an essential component of a classic Fenton or Fenton-like reaction, H2O2 can effectively decompose aqueous refractory contaminants via the large amounts of reactive oxygen species produced. There is increasing interest in developing decentralized H2O2 production methods that can greatly reduce the risks and costs of H2O2 storage, transportation, and use for oxidative reactions. The on-site activation of molecular oxygen is an ideal way to produce H2O2 for decontamination since oxygen is safe and readily available. Understanding the behaviors of O2 activation by different reductants is essential in optimizing the selectivity of H2O2 production, removal efficiency, and the functioning of a specific catalyst. In this review, the on-site generation of H2O2, including zero-valent metals, ferrous iron species, catalytic H2 reduction, and the photocatalytic activation route are critically reviewed and discussed from the fundamental aspects to their environmental applications. We hope that this review not only deepens understanding of the on-site generation of H2O2 by O2 activation, but also give pointers to further studies in this important field.