Photoelectrochemical Hydrogen Peroxide Production via Simultaneous Reduction and Oxidation Processes

Hydrogen peroxide (H₂O₂) is an essential substance in chemistry and chemical industry, while being a clean fuel. Currently, research into green and sustainable processes for producing H₂O₂ is progressing rapidly, with the aim of replacing the energy-intensive anthraquinone process used in industrial production. Among them, the photoelectrochemical (PEC) method is one that has attracted much attention, because it allows for the solar-driven production of H₂O₂ from only water and oxygen. Furthermore, highly designed PEC cells enable the simultaneous production of H₂O₂ at the anode and cathode (H₂O₂/H₂O₂-PEC cells). This review article focuses on the H₂O₂/H₂O₂-PEC cells having the potential to achieve a Faraday efficiency (η) exceeding 100% for H₂O₂, with an emphasis on the relationship between electrode materials properties and cell performances. The H₂O₂/H₂O₂-PEC cells can be classified into two types: one involving water oxidation reaction and oxygen reduction reaction (WOR/ORR), and a more recently developed type involving oxygen reduction reaction at both electrodes (ORR/ORR). Based on the fundamental principles of the H₂O₂/H₂O₂-PEC cells, we discussed the electrode material design, and then review some cutting-edge research on the WOR/ORR- and ORR/ORR-PEC cells. Finally, we summarize the conclusions, and outline challenges and perspectives in this hot topic.