Simultaneous Glycolate and Hydrogen Generation Enabled by Unassisted Photocathode-Anode Cells

Abstract

Photoelectrochemical (PEC) water splitting has emerged as a highly promising solar-driven technology for sustainable chemical synthesis. However, this photosynthesis-inspired approach is limited by slow oxygen evolution kinetics. Herein, a bias-free, energy-saving PEC system for simultaneous glycolate and hydrogen production is reported. A highly efficient PdAu catalyst on Ni foam is developed for the upgrading of ethylene glycol (EG) derived from polyethylene terephthalate (PET) plastics, which shows a high performance for electrochemical glycolate production with a low onset potential of 0.25 V vs the reversible hydrogen electrode (RHE) and a high Faradaic efficiency (FE) of 95.6% at 100 mA cm⁻². When coupled with a cuprous oxide (Cu₂O) photocathode, the constructed solar-driven PEC-HER//EGOR device achieves a photocurrent density of up to 5.6 mA cm⁻² at zero applied bias, owing to the lower potential requirement of EG oxidation than oxygen evolution reaction. Moreover, it has nearly unity hydrogen FE and 94.8% glycolate FE at 1 h of unbiased operation, showing great potential in continuous and simultaneous hydrogen production and PET-derived EG valorization without any additional bias or expensive chemicals. This work demonstrates a straightforward, energy-efficient, and environmentally benign solar-to-chemical conversion approach for integrating environmental remediation and PEC synthesis.