WO3-based electrodes fabricated by plasma electrolytic oxidation (PEO) for coupled hydrogen production and organic pollutant removal

The integration of green hydrogen production with wastewater treatment is a promising strategy for addressing the dual challenges of clean energy generation and environmental remediation. Herein, we propose an innovative class of noble metal (Pt, Pd, Ru, etc.)-free cathodes based on tungsten trioxide (WO3), fabricated via plasma electrolytic oxidation (PEO) on affordable aluminum substrates. The PEO process produced porous, adherent, and compositionally complex coatings of mixed crystalline/amorphous WO3 with embedded W0, providing low-cost and scalable electrodes for the hydrogen evolution reaction (HER), which is also effective in water containing organic contaminants. The structural and surface analyses established a clear structure property relationship, correlating WO3 content and PEO-induced morphology with both hydrogen evolution and pollutant degradation efficiency, while the electrochemical characterization revealed that both increased WO3 loading and Zn–Al layered double hydroxide functionalization improved charge transfer and HER activity. A15W, selected as the best-performing cathode, achieved up to 1 mmol cm 2 H2 generation in acidic water contaminated with model organic molecules (rhodamine B, gallic acid, and 3,4,5-trimethoxybenzoic acid), promoting at the same time pollutants electrooxidation (40-100% abatement depending on the reaction con- ditions). These findings highlight the potential WO3-based electrodes as promising, low-cost alternatives to Pt for integrated hydrogen production and wastewater treatment.