Photocatalytic Evolution of Hydrogen Peroxide: A Minireview

Hydrogen peroxide (H2O2) has demonstrated applicability in a wide range of applications, spanning from a bleaching agent in the pulp industry, environmental remediation, and fuel cell technology. Industrial scale synthesis, either by the anthraquinone method or catalytic oxidation of hydrogen gas, has serious drawbacks which are related with energy demanding and multi-step processes. An alternative green strategy involves the photocatalytic synthesis of H2O2. All that is needed is the renewable energy of the sun, a semiconducting species absorbing in the visible region, water, and oxygen. In this minireview, we describe the evolution of research milestones that have been achieved within the recent decades regarding the development of functional photocatalytic systems. In the early studies, back in the 1980’s, TiO2-based systems were mostly investigated. However, due to the large band gap of titania (3.2 eV), alternative semiconductors were studied which strongly absorb in the visible region. Thus, a variety of semiconductor families have been investigated, such as doped titania systems, other metal oxides, metal sulfides, organic semiconductors, metal-organic frameworks, carbon nitride systems, etc. In parallel, the development of functional dopants onto the surface of the main semiconductor has lead to both the inhibition of electron-hole recombination and H2O2 degradation. The current minireview collectively provides the studies of the higher H2O2 production rates and offer some suggestions for the near future.