Kumaravel, SakthivelSakthivelKumaravelDurai, ManiManiDuraiErusappan, ElangovanElangovanErusappanArun ThirumuruganSandoval-Hevia, GabrielaGabrielaSandoval-HeviaAfzal, MohdMohdAfzalDurai, MathivananMathivananDuraiLee, Dae SungDae SungLee2026-07-072026-07-072025INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 188, 152064 (2025). https://doi.org/10.1016/j.ijhydene.2025.1520640360-31991879-3487https://hdl.handle.net/20.500.12740/24718The development of cost-effective and highly efficient bifunctional materials to enhance the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a significant challenge in electrocatalytic seawater splitting. In this study, we synthesized bare zinc oxide (ZnO), ZnO/reduced graphene oxide (rGO) (ZnO@rGO), and x% RuO2/ZnO@rGO (RZR) (where x = 1.5, 2.5, 3.5, and 4.5 wt%) using sol-gel and hydrothermal methods. Their electrochemical performance was evaluated in an alkaline seawater medium (natural seawater with 1 M KOH). The 3-RZR composite supported on nickel foam (3-RZR@NF) exhibited outstanding activity, requiring only 176 mV for OER and 67 mV for HER at a current density of 10 mA/cm2. These values surpass those of IrO2@NF and approach the performance of the benchmark Pt/C@NF electrode. The catalyst also exhibited long-term stability (70 h) with minimal current fluctuations. The 3-RZR@NF||3-RZR@NF electrolyzer demonstrated superior overall water splitting, requiring lower voltages (1.47 V at 10 mA/cm2) than the conventional Pt/C@NF||IrO2@NF electrolyzer. Furthermore, the 3-RZR@NF||3-RZR@NF electrolyzer achieved high Faradaic efficiencies of approximately 91 % for the HER and 89 % for the OER, while effectively suppressing hypochlorite formation. Additionally, the 3-RZR composite showed remarkable photocatalytic degradation of methylene blue (MB) and tetracycline (TC) under sunlight, achieving near-complete MB degradation and 93 % TC removal with excellent recyclability. Reactive species trapping experiments combined with electron spin resonance analysis confirmed that •O2− and •OH radicals are the dominant reactive species responsible for the decomposition of MB and TC. In addition, liquid chromatography–mass spectrometry was employed to elucidate the degradation pathways of TC and identify its intermediate products.Articulohttps://doi.org/10.1016/j.ijhydene.2025.152064