Assessing the Neuro- and Immunotoxicity of Dissolved Ru ³⁺ from Proton Exchange Membrane Electrolyzers by Zebrafish Models

The scaling up of proton exchange membrane (PEM) electrolyzers for green hydrogen requires proactive environmental risk assessment of catalyst materials. Ruthenium (Ru)-based catalysts are increasingly favored over iridium (Ir) due to cost advantages. However, their tendency to dissolve and release Ru³⁺ ions under operational conditions poses a potential but unexplored ecological threat. This study demonstrates that Ru³⁺ exhibits significantly higher acute toxicity than Ir³⁺ in zebrafish, with a 48 hpf LC₅₀ of 55.3 mg/L. Transcriptomic analysis revealed 4,619 differentially expressed genes, predominantly enriched in neurodevelopmental and immunotoxic pathways, leading to reduced hatching, immune dysregulation, and locomotor defects. Molecular docking identified key protein targets (CASP3, DLG4, GRIN2B, and GSTO1) underlying the toxicity. These findings establish a preemptive safety benchmark for Ru³⁺ and underscore the necessity of incorporating ecotoxicological considerations into the sustainable design of PEM electrocatalysts. We advocate for an expanded ASC-E (Activity, Stability, Cost, Environment) paradigm that integrates environmental biosafety as a core metric.