Sustainable hydrogen peroxide production based on dopamine through Janus-like mechanism transition from chemical to photocatalytic reactions

With increasing interest in hydrogen peroxide (H₂O₂) as an environmentally friendly oxidant for environmental remediation and a promising liquid fuel, we present herein a novel method for green and sustainable H₂O₂ production using versatile dopamine-based materials, demonstrating the conversion of H₂O₂ generation mechanism from a chemical to a photocatalytic process along with the structural transformation of dopamine to polydopamine. During the auto-oxidation of dopamine in the presence of oxygen, which involved the transition of catechol to hydroquinone groups and the ring closure of the amine group, H₂O₂ was chemically generated at a rate of 1.61 mmol g^-1h⁻¹ without an extra electron donor and additional energy sources. In contrast, self-polymerized polydopamine exhibited an effective photocatalytic H₂O₂ generation at a rate of 0.53 mmol g^-1h⁻¹ owing to its visible light absorptivity and semiconducting property. We anticipate that these unique properties of dopamine will provide a new class of organic-based, highly efficient solar-to-H₂O₂ conversion and sustainable energy systems in the future.