Photocatalytic hydrogen peroxide production toward quantum yields exceeding 100%

Abstract

Hydrogen peroxide (H₂O₂) is not only an important substance widely used in large quantities in chemistry and the chemical industry, but also a promising clean fuel and oxidant for fuel cells. In recent years, photocatalytic H₂O₂ synthesis from O₂ and/or water has been actively researched with the aim of green on-site production. The intrinsic reaction efficiency can be evaluated by the external quantum yield or apparent quantum yield defined by the ratio of the number of H₂O₂ molecules produced to the number of incident photons. Remarkably, external quantum yields of approximately 100% have already been achieved in several photocatalytic H₂O₂ generation systems via the oxygen reduction reaction (ORR). H₂O₂ has a unique property of being able to be produced through the ORR and the water oxidation reaction (WOR). Taking advantage of this, research into photocatalytic H₂O₂ production via simultaneous reduction and oxidation processes (H₂O₂/H₂O₂-PCP) has recently begun. This feature article focuses on H₂O₂/H₂O₂-PCP, which has the potential to produce H₂O₂ with a quantum yield of over 100%. First, we discuss the fundamentals of materials and reaction design for constructing highly efficient H₂O₂/H₂O₂-PCP systems. Afterwards, several cutting-edge studies on H₂O₂/H₂O₂-PCP are highlighted to learn effective approaches for enhancing the quantum yield and discussed in terms of the materials and reaction design. Finally, we summarize the conclusions and outline challenges and perspectives in this hot topic to stimulate future research.