Precious Metal-Free Artificial Leaf for Photosynthesis of Hydrogen Peroxide from Water

Hydrogen peroxide (H₂O₂) is recognized as an environmentally friendly oxidant with a wide range of applications, as well as a promising future energy carrier compared to hydrogen. Light driven and electrochemical production of H₂O₂ have gained significant interest as promising alternatives to the energy-intensive anthraquinone process. The two main approaches for the (photo)electrochemical production of H₂O₂ are the water oxidation reaction (WOR) and the oxygen reduction reaction (ORR). Considering the scarcity of noble metals, it is critical to develop successful high-performing electrocatalysts based on earth-abundant sources, thus adhering to principles of Green and Sustainable Chemistry. Herein, the use of the recently developed FeO_x nanoparticles (NP) catalyst as a photocathode, circumventing catalyst deactivation and oxidation, is reported. The FeO_x NP photocathode exhibited an increased catalytic current by 41% under illumination, demonstrating the advantage of a photoelectrochemical (PEC) setup. Combining the FeO_x NP photocathode for ORR with a Ti-doped α-Fe₂O₃ photoanode for WOR, robust PEC performance is successfully achieved in bias-free conditions. The structural integrity of the FeO_x NP photocathode is preserved without degradation or oxidation for extended periods of irradiation of up to 10 h testimony of a benign and robust process.