Bifunctional RuO2/ZnO@rGO electrocatalysts for efficient alkaline seawater electrolysis and solar-light degradation of organic pollutants

초록

The 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 hydro-thermal 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 center dot O2-and center dot 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.

키워드