Tandem Photoelectrochemical Cells for Hydrogen Peroxide With Glyceric Acid Production

ABSTRACT While photoelectrochemical (PEC) oxygen reduction for hydrogen peroxide (H 2 O 2 ) production offers a sustainable alternative to the energy‐intensive and detrimental anthraquinone process for industrial production, continuous and stable long‐term operation remains challenging due to sluggish charge transfer kinetics and poor corrosion resistance of the photoelectrode. Herein, we synthesized a heterojunction photocathode comprising CuO and W‐doped CuBi 2 O 4 decorated with Pd nanoparticles (Pd:CuO/W‐CBO) for efficient and stable PEC H 2 O 2 generation. The optimized photocathode achieves an average Faradaic efficiency exceeding 90% with a low onset potential of 1.08 V RHE , enabling a stable operation for over 50 h at 0.7 V RHE . The CuO overlayer effectively suppresses dissolution of Cu and Bi species, improving the stability of CuBi 2 O 4 ‐based photoelectrodes. More importantly, a bias‐free PEC system utilizing the Pd:CuO/W‐CBO photocathode and a Pt/TiO x anode was constructed for simultaneous solar‐driven H 2 O 2 production and electrochemical glycerol oxidation to high‐value chemicals. This unassisted system delivers a current density of 3.75 mA cm −2 under one sun illumination. Further employing a large‐scale photocathode (10 cm 2 ) enables H 2 O 2 and C 3 chemical production rates of 250.4 and 127.6 µmol h −1 , respectively. Regulating H 2 O 2 permeation using an anion exchange membrane considerably enhances the selectivity to 56% for oxidation of glycerol to glyceric acid, markedly outperforming systems using proton/cation exchange membranes (∼20%). Additionally, the cathodically generated H 2 O 2 enables rapid water disinfection, achieving >99.9% bacterial inactivation within 180 min. This work demonstrates a scalable PEC platform for stable concurrent solar‐driven H 2 O 2 generation and glycerol valorization while enabling energy conversion.